VEGETATED ROOF SYSTEMS: DESIGN, PRODUCTIVITY, RETENTION, HABITAT, AND SUSTAINABILITY IN

GREEN ROOF AND ECOROOF TECHNOLOGY

DISSERTATION

Presented in Partial Fulfillment of the Requirements for

the Degree Doctor of Philosophy in the Graduate School of The Ohio State University

By

Reid R. Coffman, M.L.A.

* * * * *

The Ohio State University 2007

Dissertation Committee Approved by Professor: Claudio Pasian, Adviser Professor: Jane Amidon Professor: Jay Martin _____________________________ Professor: Tom Waite Adviser Horticulture and Crop Science Graduate Program

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ABSTRACT

The environmental technology of vegetated roof systems, also called

green roofs or ecoroofs, depends on collaboration between designers and

scientists. But this collaboration is difficult to carry out due to well-entrenched

differences in disciplinary methods. To compensate this dissertation attempts to

improve our conceptualization and dissemination of vegetative roof system

projects and to extend our scientific knowledge of how these systems function.

In Chapter 1, I offer designers a framework for the conceptualization of ecoroof

projects and dissemination of knowledge about such systems. Problems in

conceptualization are caused by ignorance, generality, complexity and obscurity,

while problems in dissemination are created by a lack of communication and the

number of research projects. I propose a design-research framework for the

inclusion and communication of research agendas into design projects. This

framework provides a design-research model and design-research domains to

direct future projects and enhance collaboration.

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Innovation in ecoroof technology persists, but often occurs with assumed

benefits possessing unknown consequences. Therefore, in Chapter 2, I describe

the first scientific study, which was designed to evaluate experimentally the effect

of substrate depth on net primary productivity, water retention, and water quality.

My data revealed that deep substrate roofs retained 18% more rainwater while

producing 2.5 times more biomass than shallow substrate roofs. Roofs using

water recycling or run-on water produced up to 26% more biomass than those

receiving only direct precipitation and did so without any significant reduction in

retention. All roofs showed low productivity compared to grassland and forest

ecosystems. Water quality was lowest in deep roofs, yet remained higher than

receiving streams. This chapter demonstrates that ecoroof innovation should

continue as a part of the technology’s development.

The use of ecoroofs for the conservation of urban biodiversity is

advocated by enthusiasts, yet the affects are largely unknown. In Chapter 3, I

quantify animal diversity for several taxa on two vegetated roof systems and

promote a methodological approach for such studies. I used a rapid assessment

method to quantify the diversity of insects, spiders and birds on these ecoroofs

based on relative abundance data. The Rènyi family of diversity indices was

used to compare diversity between the two ecoroofs. My data revealed relatively

low similarity between the species assemblages, but a relatively strong similarity

in community structure. Overall, the intensive ecoroof supported slightly higher

diversity.

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Finally, the overriding support for implementing ecoroof technology

centers on the idea of improving urban sustainability, which goes unmeasured.

Therefore, in Chapter 4, I use emergy analysis to quantify and compare the

sustainability of three vegetated roof systems: an agricultural roof garden, a

shallow-substrate ecoroof, and a deep-substrate ecoroof. The shallow-substrate

ecoroof was the most sustainable (least unsustainable) of the three, followed by

the deep-substrate ecoroof and the agricultural roof garden. All three systems

were less sustainable than various agricultural practices, while being more

sustainable than conventional landscapes, urban gardens and cities. These

results confirm that vegetated roof systems can improve the sustainability of a

city, but are reliant on many non-renewable resources for their construction and

upkeep.

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DEDICATION

This work is dedicated

to my parents, Sally and Larry Coffman,

and my wife, Kelly Coffman,

for their faithful support.

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ACKNOWLEDGMENTS

I wish to thank my main advisor, Dr. Claudio Pasian, for the intellectual

support, and the creation of a well-balanced environment of learning and growth,

and his patience in undertaking such an interdisciplinary effort that was underway

prior to his involvement.

I wish to thank my sustainability chapter advisor, Dr. Jay Martin, for his

educational support and encouragement from the very early stages of this

endeavor, through beginning discussions in classroom teaching to the academic

guidance of this project’s development.

I wish to thank design chapter advisor, Professor Jane Amidon, for her

fresh perspective provided during mid-project stage, and the contribution of a

design perspective and methods connecting the various involved disciplinary

investigations to landscape architecture.

I wish to thank my habitat chapter advisor, Dr. Tom Waite, who provided

the much needed foundational research guidance in this project and who made

himself available in times of need during my transition period between main

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advisors. His help interpreting the concepts and applications of ecology were

irreplaceable and deeply appreciated.

I am grateful to the following for their assistance: Dr Norman Johnson

(Insect identification) and Dr Richard Bradley (Arachnid identification) and

Graham Davis, researcher of The Ohio State University for their guidance and

assistance. The Wexner Center for the Performing Arts and the Ford Motor

Company for their cooperation in providing information and access and

particularly Don Russell for his involvement. The Department of Horticulture and

Crop Science at OSU, the National Wildlife Federation (NWF) and the Ohio

Agricultural Research and Development Center (OARDC) for their financial

support. The several anonymous peer reviews provided by members from the

research committee of the Greening Roofs for Healthy Cities organization.

Lastly, I wish to thank Martin F. Quigley, PhD for his initial encouragement

and support of this project.

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VITA

April 25, 1970 ……………………………..Born, Battlecreek, MI 1993 ………………………………………..B.S. Education, University of Missouri 1998 ………………………………………..M.L.A. Architecture, University of

Colorado 2001 ………………………………………..Adjunct Faculty, College of Architecture The Ohio State University 2002-2004………………………………….Graduate Assistant, College of Food, Agricultural and Environmental Sciences The Ohio State University 2004 ……….……………………………….Campus Ecology Fellowship National Wildlife Federation The Ohio State University 2004-present……………………………….Assistant Professor, College of Architecture, University of Oklahoma

PUBLICATIONS Coffman, R. 2007 “Understanding Assignments: Improving the Edge Condition of

a Mitigation Wetland ” Council of Educators of Landscape Architecture Conference, State College, PA

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Coffman, R. 2007 “Ecoroofs as Habitat? Assessing Biodiversity Across Green Roof Class.” Greening Rooftops for Sustainable Communities, Minneapolis, MN

Coffman, R. and Davis, G., 2005 “Insect and Avian Fauna Presence on Ford’s

River Rouge Plant.” Greening Rooftops for Sustainable Communities, Washington D.C

Coffman, R. and Martin, Jay 2004 “The Sustainability of an Agricultural Roof

Garden” Greening Rooftops for Sustainable Communities, Portland, OR

FIELDS OF STUDY Major Field

Horticulture and Crop Science Specialization

Urban Ecology Plant and Systems Ecology

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TABLE OF CONTENTS

ABSTRACT ...........................................................................................................ii DEDICATION ....................................................................................................... v ACKNOWLEDGMENTS .......................................................................................vi VITA ...................................................................................................................viii TABLE OF CONTENTS ....................................................................................... x LIST OF FIGURES ............................................................................................. xiii LIST OF TABLES .............................................................................................. xvii

CHAPTER 1 AMBIGUOUSLY GREEN? IMPROVING COMMUNICATION IN ECOROOF TECHNOLOGY THROUGH A DESIGN-RESEARCH FRAMEWORK ................................................................................................ 1

1.1 ABSTRACT .................................................................................................... 1 1.2 INTRODUCTION .............................................................................................. 3

1.2.1 Overview .............................................................................................. 3 1.2.2 Vegetated Roof System Terms and Types........................................... 5 1.2.3 Vegetated Roof System History ........................................................... 7

1.3 BROAD SHIFT TO ENVIRONMENTAL SERVICES .................................................. 9 1.3.1 Sustainability and Environmental Services........................................... 9 1.3.2 Environmental Services of Vegetated Roof System ........................... 11

1.4 SPECIFIC PROBLEMS .................................................................................... 14 1.4.1 Current problems in dissemination ..................................................... 14 1.4.2 Current problems in conceptualization ............................................... 17

1.5 PROPOSED METHODOLOGY.......................................................................... 26

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1.5.1 The design model precedent .............................................................. 26 1.6 DESIGN-RESEARCH DOMAINS....................................................................... 28

1.6.1 Productivity Domain............................................................................ 29 1.6.2 Biodiversity Domain............................................................................ 32 1.6.3 Energy ................................................................................................ 35 1.6.4 Nutrient Cycling Domain..................................................................... 37 1.6.5 Hydrologic Cycle Domain ................................................................... 39 1.6.6 Social Understanding and Stewardship.............................................. 43

1.7 SAMPLE APPLICATIONS ................................................................................ 45 1.7.1 Rosetti Building .................................................................................. 46 1.7.2 Ford Assembly Plant Ecoroof ............................................................. 48 1.7.3 Latter Day Saints Conference Center................................................. 49

1.8 DISCUSSION................................................................................................ 52 1.9 CITATIONS .................................................................................................. 54

CHAPTER 2 PRIMARY PRODUCTIVITY, WATER RETENTION AND LEACHATE QUALITY IN TWO ALTERNATIVE ECOROOF DESIGNS........ 61

2.1 ABSTRACT .................................................................................................. 61 2.2 INTRODUCTION ............................................................................................ 62

2.2.1 Ecoroofs ............................................................................................. 62 2.3 MATERIAL AND METHODS.............................................................................. 69

2.3.1 Constructed Plots ............................................................................... 69 2.3.2 Experimental Design .......................................................................... 73 2.3.3 Data collection.................................................................................... 73 2.3.4 Data analysis...................................................................................... 74

2.4 RESULTS .................................................................................................... 74 2.4.1 Biomass.............................................................................................. 74 2.4.2 Retention ............................................................................................ 78 2.4.3 Water Quality...................................................................................... 82 2.4.4 Interactions......................................................................................... 87

2.5 DISCUSSION................................................................................................ 92 2.6 CONCLUSIONS............................................................................................. 96 2.7 CITATIONS .................................................................................................. 98

CHAPTER 3 ECOROOFS AND BIODIVERSITY: ASSESSING ANIMAL DIVERSITY ON TWO TYPES OF VEGETATED ROOFS........................... 103

3.1 ABSTRACT ................................................................................................ 103 3.2 INTRODUCTION .......................................................................................... 104 3.3 VEGETATED ROOF SYSTEMS AND ANIMAL DIVERSITY ASSESSMENT............... 107

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3.4 METHODS ................................................................................................. 112 3.5 RESULTS .................................................................................................. 116 3.6 DISCUSSION.............................................................................................. 121

3.6.1 Combining Rapid Assessment and the Rènyi method for quantifying diversity ..................................................................................................... 122 3.6.2 Ecoroof Biodiversity and Conservation............................................. 123

3.7 CONCLUSIONS........................................................................................... 126 3.8 CITATIONS ................................................................................................ 128

CHAPTER 4 EMERGY EVALUTION OF THE PRODUCTIVITY AND SUSTAINABILITY OF THREE VEGETATED ROOF SYSTEMS ................ 132

4.1 ABSTRACT ................................................................................................ 132 4.2 INTRODUCTION .......................................................................................... 133 4.3 METHODS ................................................................................................. 138

4.3.1 Systems Descriptions ....................................................................... 138 4.3.2 Emergy Flows and Definitions .......................................................... 139 4.3.3 Emergy Analysis............................................................................... 142

4.4 SUB-ANALYSIS OF EXPANDED CLAY ............................................................. 150 4.4.1 The emergy analysis of expanded clay ............................................ 150

4.5 RESULTS .................................................................................................. 153 4.5.1 Renewable ....................................................................................... 153 4.5.2 Purchased Resources ...................................................................... 154 4.5.4 Yields and Specific Emergy.............................................................. 155 4.5.5 Emergy Indices................................................................................. 156

4.6 DISCUSSION.............................................................................................. 158 4.6.1 Limitations ........................................................................................ 158 4.6.2 Vegetated Roof Systems Sustainability and Productivity ................. 160 4.6.3 Comparison to other landscape systems.......................................... 162 4.6.3 The City and Vegetated Roof Systems............................................. 167 4.6.4 The Perception of the Vegetated Roof Technology.......................... 168 4.6.5 Improved Sustainability .................................................................... 169

4.7 CONCLUSIONS........................................................................................... 172 4.8 CITATIONS ................................................................................................ 174

REFERENCES................................................................................................. 179 APPENDIX A VEGETATED ROOF SYSTEM DESCRIPTIONS...................... 193 APPENDIX B STATESTICAL ANALYSIS ....................................................... 197 APPENDIX C EMERGY CALCULATIONS..................................................... 200 APPENDIX D COPYRIGHT PERMISSION ..................................................... 209

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LIST OF FIGURES

Figure Page 1.1 Two vegetated roof system classes: The Ford Motor Assembly Plant,

Dearborn, MI USA (left) is an extensive system (<15.24cm of soil) consisting of a shallow rock-based substrate containing exotic succulents that regulate energy and stormwater, while the Fairmont Waterfront, Vancouver, BC Canada (right) is an intensive system consisting of raised beds of thick, rich topsoil (with planters >1m deep) producing local produce and herbs……………………………………….......7

1.2 The contributing effects persisting in ecoroof projects, shown above in

ovals with arrows indicating cumulative influence………………………... 19 1.3 An example of the effect of ignorance at Ford Assembly Plant ecoroof

Dearborn MI. Irrigation is used past the plant establishment period in order to maintain a visual appearance likely impacting its main goal of stormwater retention…………………………………………………………..21

1.4 The complex intellectual design-research model allows research and

design collaboration through semi-alternating phases. The model begins with current knowledge that can be applied to the site and defined through discrete elements that can be constructed, assessed and disseminated. The knowledge returns to inform future projects………………………………………………………………………....27

1.5 A diagram of ecoroof design-research domains with example criteria

are shown in circles and two-way arrows indicate potential influence…..29 1.6 An illustrative image-diagram for the Rosetti Building ecoroof in Zurich,

Switzerland prioritizing biodiversity, productivity, energy, and hydrologic cycling (shown in circles) in the project agenda. The background image

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shows the site while text explains the proposal, means of installation and assessment criteria………………………..………………………....…..47

1.7 An illustrative image-diagram for the Ford Assembly Plant Ecoroof,

Dearborn, MI USA prioritizing energy, hydrologic cycling and stewardship (shown in circles) in the project agenda The background image shows the site while text explains the proposal, means of installation and assessment criteria. ………………………………….…..49

1.8 An illustrative image-diagram for the Church of Latter Day Saints

Conference Center ecoroof, Salt Lake City, UT USA prioritizing stewardship, biodiversity and energy (shown in circles) in the project agenda. The images show the site while text explains the proposal, means of installation and assessment criteria. …………………………..51

2.1 General view of the plots located in the Waterman Farm at the OSU

campus, Columbus, OH……………………………………………………....71 2.2 Plot Layout. Class: e (extensive) or i (intensive). Alternative: a (apron),

d (direct), r (recycle) and c (control). Aprons are shown as attached squares with a X drawn on them………………………………………….…72

2.3 Mean productivity measured as whole plant biomass by class (±SE)

(P-value < 0.001, 95% CI). Bars with same letter are not significantly different.………………………………………………………………………...75

2.4 Mean productivity measured as whole plant biomass by alternative

(± SE.) (All P-values are < 0.05, 95% CI). Bars with same letter are not significantly different.……………………………………………………..76

2.5 Mean productivity measured as whole plant biomass by alternative

and class (± SE.) (All P-values are < 0.05, 95% CI). Bars with same letter are not significantly different …………………………………………..77

2.6 Mean productivity measured as whole plant biomass per species

(± SE.) (P < 0.001, 95% CI). Bars with same letter are not significantly different.………………………………………………………….78

2.7 Mean water retention by class (± SE). (P < 0.001, 95% CI) Bars with

same letter are not significantly different……………………………….…..79 2.8 Mean water retention by alternative irrespective of class (± SE). (All P

values are < .05, 95% C.I.) Bars with same letter are not significantly different………………………………………………………………………....80

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2.9 Mean water retention of alternative by class (± SE). (All P-values are < .05, 95% C.I.). Bars with same letter are not significantly different……………………………………………………………………...….81

2.10 Mean water retention of natural and simulated storms (± SE). (P < 0.05,

95% CI) Bars with same letter are not significantly different.…………..…82 2.11 Mean Electrical Conductivity (EC) in the runoff water by class (mean ±

SE). (P < 0.001, 95% CI). Bars with same letter are not significantly different ..…………………………………………………………..…………..83

2.12 Mean Electrical Conductivity (EC) in the runoff by alternative

irrespective of class (± SE). (All P values are < .05, 95% C.I.) Bars with same letter are not significantly different…………………..…....84

2.13 Mean Electrical Conductivity (EC) in the runoff by alternative and

class (± SE). (All P values are < .05, 95% C.I.) Bars with same letter are not significantly different……………………………...……..…….85

2.14 Mean pH in the runoff by alternative irrespective of class (± SE). (All P

values are < .05, 95% C.I.) Bars with same letter are not significantly different……………………………………………………………………..…..86

2.15 Mean pH in the runoff by alternative irrespective of class (± SE). (All P

values are < .05, 95% C.I.) Bars with same letter are not significantly different…………………………………………………………………..……..87

2.16 Linear regression of biomass predicted by retention shown with

observed values as symbols ( y = 6.3496x - 70.801 R2= 0.8262).…… …88 2.17 Linear regression of biomass predicted by retention by alternative

regardless of class shown with observed values as symbols. (Direct; y = 5.1658x - 60.425 R2 = 0.976 Recycle, y = 6.4007x - 61.433, R2= 0.971. Apron y = 9.0247x - 138.61, R2= 0.9382)………… ……..…..89

2.18 Mean moisture tension in the substrate by class observed values as

symbols an predicted values as an exponential curve; extensive (y = 4.3261e 0.2179x) and intensive (y = 3.2342e 0.2283x).………. ………….….. .90

2.19 Mean moisture tension in the substrate for the extensive class

alternatives shown observed values as symbols an predicted values as an exponential curve; direct y = 4.3261e 0.2179x), apron (y = 4.298e 0.2394x), control (y = 3.4185e 0.2795x) and recycle (y = 3.0663e 0.2025x ). ….91

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2.20 Mean water tension in the substrate for the intensive class alternatives shown with observed values as symbols an predicted values as an exponential curve; direct (y = 3.2342e 0.2283x), apron (y = 3.5781e 0.2376x), control (y = 2.6034e 0.201x) and recycle (y = 2.5819e 0.1769x …………………………………………………………….92

3.1 Map showing the two study sites site e and site i………………………...107 3.2 Relative abundance of insect orders at sites e and i………………….… 119 3.3 Curves represent diversity Hα (y-axis) of insects, spiders and birds for both

site e (dashed) and site i (solid) across scales α (x-axis), with integer values of α corresponding to conventional metrics of diversity: 0 (richness), 1 (Shannon’s), 2 (Simpson’s), 3 (Berger-Parker) and 4 (infinity). The curves indicate higher diversity at site i than site e.…….120

3.4 Diversity profiles describing both site e (dashed) and site i (solid) for:

a) all taxa, b) spiders, c) insects, and d) birds…………………………….121 4.1 The emergy system diagram of the agricultural roof garden. Inputs

to the system (circles) are quantified in Table 4.1 corresponding to the number shown. Interactions occur within the system boundary (larger rectangle) and outputs leaving the system are shown as arrows. ....….146

4.2 The emergy system diagram of the shallow substrate ecoroof. Inputs

to the system (circles) are quantified in Table 4.1 corresponding to the number shown. Interactions occur within the system boundary (larger rectangle) and outputs leaving the system are shown as arrows……….147

4.3 The emergy system diagram of the deep substrate ecoroof. Inputs

to the system (circles) are quantified in Table 4.1 corresponding to the number shown. Interactions occur within the system boundary (larger rectangle) and outputs leaving the system are shown as arrows……....148

4.4 The emergy system diagram of expanded clay. . Inputs to the system

(circles) are quantified in Table 4.1 corresponding to the number shown. Interactions occur within the system boundary (larger rectangle) and outputs leaving the system are shown as arrows………………………..152

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LIST OF TABLES

Table Page 1.1 Green roof research occurring in public institutions………………….…….13 3.1 The two study sites compared by categorical.…………………….......….113 3.2 Collected Taxa from the two study sites …………………………..…117-118 4.1 The emergy table of the vegetated roof systems quantifies inputs and

outputs from raw units, which are multiplied by the emergy per unit (transformity) to get a total emergy value for each input. Output is the sum of the all emergy values……….……………………………………….149

4.2 Substrate composition table of the three vegetated roofs systems by

volume and percentage per cubic meter. …………………………………150 4.3 Emergy table of expanded clay quantifies inputs and outputs from raw

units, which are multiplied by the emergy per unit (transformity) to get a total emergy value for each input. Output is the sum of the all emergy values. ………………………………………………………………………..153

4.4 Emergy indices table describing the three vegetated roofs systems and

branched flow of the agricultural roof garden. ………………………...157 4.5 Comparative landscapes table describes the values of the three

vegetated roof systems and ten previously evaluated landscapes. ……166 B.1 ANOVA (General Linear Model) for whole plant biomass (per plant per plot) versus class, alternative, plant………………………………………..196

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B.2: ANOVA (Friedman’s) for biomass (per plot) amongst class………….....197 B.3: ANOVA (Friedman’s) for biomass (per plot) amongst alternative……....197 B.4: ANOVA (General Linear Model) for Retention……………………………197 B.5: ANOVA (General Linear Model) for Electrical Conductivity……………..198 B.6: ANOVA (General Linear Model) for pH……………………………………198

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CHAPTER 1

AMBIGUOUSLY GREEN? IMPROVING COMMUNICATION IN ECOROOF

TECHNOLOGY THROUGH A DESIGN-RESEARCH FRAMEWORK

1.1 Abstract

This study offers to design disciplines a framework for conceptualizing,

developing design methods and establishing assessment criteria for vegetative

roof systems. The study’s framework is intended to function as a designer’s

‘toolkit’ to assist in their communication with researchers, while offering

opportunities to direct design projects toward research applicability and

dissemination. Excluded from this study is an equivalent ‘toolkit’ assisting

researches in understanding the design process. The original intent of this study

was to combine design and scientific research methodologies into a singular

(interdisciplinary) process in order to assist developing solutions in ecoroof

technology. The integration of design and scientific research proved difficult as

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established methodologies governing the practice and dissemination of

disciplinary work remained distinct. Poor communication between design

professionals and applied researchers persists as an impediment in the

development of the technology.

Therefore, this study proposes a first step towards rectify the current

professional gap by connecting design and research through the use of both a

design model and design-research domains. Beginning with a discussion of the

available literature, the problems associated with research dissemination and

project conceptualization are described. The design profession factors

contributing to the problem include: ignorance, generality, complexity and

obscurity. To improve project conceptualization a design-research model is

offered to establish greater clarity in project goals through the use of design-

research domains. Six design-research domains are proposed to identify the

multidisciplinary initiatives of ecoroofs: productivity, biodiversity, energy balance,

nutrient cycling, hydrological cycling, and stewardship. The domains are based

on published and developing research agendas within ecoroof technology and

are intended to strengthen project development while providing research

legitimacy. The design-research domains are applied to sample applications of

past projects. The domains are shown as image-based illustrative diagrams

inclusive of disciplinary perspective while displaying the hierarchy of project

goals. Finally, further opportunities for disciplinary collaboration in ecoroofs and

design are discussed.

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1.2 Introduction

1.2.1 Overview

Although ecoroof technology has recently experienced a rapid rise in

popularity as a green building practice, it remains plagued by problems of clarity

and miscommunication that are hampering its development, implementation and

effectiveness (Bruce 2005; Calkins 2005). These problems are caused by

general issues, such as a shared understanding of sustainability by involved

members, and specific issues, such as misinterpreting disciplinary knowledge.

However, one “weak link” that has been expressed by Bruce (2005) is the poor

relationship between design and research professions. Designers, lack effective

relationships with researchers, and therefore contribute to technological

problems through their leadership in project conceptualization and subsequently

reduce the effectiveness of knowledge dissemination. Therefore, this study

provides designers with a ‘toolkit’ to address these problems through improved

association with, and recognition of research contributions.

Many issues contribute to these problems. One is the current shift from a

general concept of sustainability to the concept of ecosystem services, which are

the environmental benefits society receives from the natural processes of

ecosystems (Costanza et al. 1997; Daily 1997; de Groot et al. 2002). This broad

epistemological shift is influencing the way team members approach a project. In

addition to such broad changes, many disciplines are trained categorically and

have knowledge and methods considered exclusive. This creates a series of

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problems in the sharing of knowledge (dissemination) and in the development of

the project (conceptualization).

Most recently, calls for greater communication between the disciplines

involved in design and research have been made (Grant and Jones 2005;

Oberlander and Whitelaw 2005; Dunnett 2006). One framework for managing the

complexity of these projects has been proposed by Grant and Jones (2005).

However, the framework does not consider several existing research areas,

overlooks design innovation as a part of research objectives, and, most

importantly, does not offer a method to actively connect designers with

researchers.

This study shows that design and research exist simultaneously but are

not currently coordinated. Design continues to be committed to aesthetic-only

design proposals that compromise and contradict understood performance,

which is a risk of professional marginalization. In my opinion, research, on the

other hand, is developing in relative isolation, at times repeating itself, but overall

developing the knowledge of the technology. In the worst case scenario, the

fields come together as knowledge is applied as design regulation which often

results in professional contention. The attempt of this study is to inform

designers on how they can improve their association with researchers by better

understanding current research agendas and how to include research input into a

design project.

Therefore, this chapter proposes a framework to rectify the current

situation by connecting design and research through the use of a design model

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and design-research domains. The chapter begins with description of the

selected literature reviews used in this study, an explanation of ecoroof types and

terminology; a discussion of the broad shift to environmental services, and

discusses the specific problems with the technology. From that point, the new

methodology is proposed by explaining the design model precedent and design-

research domains. To further understand how the domains function, they are

applied to three projects as sample applications. Lastly, a discussion of the

design-research methodology is provided.

1.2.2 Vegetated Roof System Terms and Types

A vegetated roof system is simply vegetation growing on a building

rooftop. This is a generalized term that has been used informally to discuss all

types roof greening. The more specific terms used to describe vegetated roof

systems are ecoroof, living roof, brown roof, roof garden and green roof, which

are more distinctive terms, yet are often used interchangeably. Ecoroof and

living roof have been associated with systems that complete an apparent season

cycle, such as dormancy due to heat or cold. Therefore, they are understood to

be an expression of an ecological or a living condition. These two terms have

been used in the Western United States. Brown roofs are, on the other hand,

associated with the urban reclamation process in which disturbed on-site soils

are used as growing medium for vegetation. This term has been used in the

United Kingdom. In addition, roof garden, the oldest and most common term, is

associated with a contrived aesthetic space for human inhabitation.

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The term green roof has two connotations: one is more specific, signifies a

thin green layer of substrate and vegetation, not intended for human inhabitation;

the other is a broad meaning that includes all forms of roof greening. Commonly,

the use of the term green roof implies that the entire roof is covered with a layer

of impervious membrane, which is topped with soil and vegetation in order to

optimize the site-specific and community environmental benefits (Peck and Kuhn

2001; Scholz-Barth 2001). Occasionally, the term green roof will be conjoined

with other roof descriptors such as ‘agricultural green roof’ or ‘green roof garden’.

At this time, no universal taxonomy, or agreement on the terminology,

exists for this technology. Miller (2004) points out that these terms are all

prescriptive, and none are currently based on descriptive performance factors.

This is likely to be the reason that all terms are used interchangeably, often

overlapping, and frequently conjoined. Throughout this chapter, the term

vegetated roof system or ecoroof will be used when referring to a broad inclusive

group, and green roof when speaking about the more discrete systems known as

the extensive classes.

The two accepted classes of vegetated roof systems are based largely on

structure and to a lesser degree on function. The first class is an extensive

system consisting of less than 10 cm of substrate and allowing for only a few

plant species. The other class is an intensive system consisting of more than 30

cm (12”) of soil medium and allowing numerous plants species (Peck et al. 1999;

Dunnett and Kingsbury 2004). Examples of these two classes are shown in Fig

1.1.

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Figure 1.1. Two vegetated roof system classes: The Ford Motor Assembly

Plant, Dearborn, MI USA (left) is an extensive system (<15.24cm of soil)

consisting of a shallow rock-based substrate containing exotic succulents that

regulate energy and stormwater, while the Fairmont Waterfront, Vancouver, BC

Canada (right) is an intensive system consisting of raised beds of thick, rich

topsoil (with planters >1m deep) producing local produce and herbs.

1.2.3 Vegetated Roof System History

The concept of roof greening has two histories: one of opulence and the

other of economy. As explained by Osmundson (2001), the luxury of roof

greening for wealth and power dates back to before 2000 BC. Works such as the

Hanging Gardens of Babylon, The Ziggurat of Nanna and the 19th-century

Kremlin all possess environments of abundant vegetation created for a ruling

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class as demonstrations of their affluence. These were technological marvels of

their time period, requiring immense labor for construction and maintenance, and

in the process consuming amounts of vast resources. On the other hand, the

thrifty use of locally available materials, such as sod, by needy individuals, to

protect and insulate their dwellings, has been a part of many cultures for equally

as long. Northern European cultures have conserved examples of these works

as a part of national heritage sites. These examples are made of local soils and

plants and placed on small dwellings to be used almost solely to cool the

structure during intense heat or warm the structure during intense cold. In

America, an example of this is European settlers using sod roofs in dwellings on

the Great Plains.

Although credit for the contemporary concept of roof greening can be

attributed to the Austrian artist Friedensreich Hundertwasser, the first recorded

English-language use of the contemporary term “green roof” may have been

Kohler’s (1990) book section on urban ecology. Shortly after, the subject was

published as a book topic by Johnston and Newton (1993), while the first

academic journal publication in English was cited using the term “green roof” do

not appear until 1998 in the analysis for heating and cooling benefits by

Eumorfopoulou (1998) and Palomo Del Barrio (1998). In 2003, for the first time

the English-language listings of academic records using the term “green roofs”

climbed out of the single digits. Many of the English-language written popular

articles cite German studies. The German citations occur in academic journals,

trade journals, conference proceedings and self published institutional reports.

9

The term “ecoroof” is a more recent, synonymous term employed by western

North American professionals whose landscapes are not perennially green in

color (Lipton 2003). It is used in this dissertation because it implies local or

regional context and an ecosystem approach.

Although growing vegetation on a rooftop is an ancient practice, the

current technology is a very recent development in North America. There

remains a large body of untranslated work regarding ecoroof technology from

Europe, specifically Germany which has been best illustrated by Mentens et al.

(2003). Some of this work has made its way to North America through trade and

manufacturer information. In the last five years, over a dozen North American

universities have begun research on vegetated roof systems.

1.3 Broad Shift to Environmental Services

1.3.1 Sustainability and Environmental Services

As sustainability remains a governing principle for community

development, the focus on discrete criteria for determining sustainability is

beginning to supplant the general measures of sustainability. The shift in focus

to performance criteria for constructed landscapes such as ecoroofs is related to

the shift in understanding the ecosystem benefits provided by landscapes.

The most widely used definition for sustainability was offered by the UN

World Commission for the Environment and Development (WCED). In its report,

entitled Our Common Future, the WCED conflates sustainability with economics

under the concept of sustainable development. “‘Sustainable development’ is

10

development that meets the needs of the present without compromising the

ability of future generations to meet their own needs” (WCED 1987). This

generality was criticized and expanded upon further defining “sustainable

development” through “sustainable growth,” “sustainable use,” and “sustainable

economy” (Munro and Holdgate 1991). All of these failed to make sustainability

measurable.

In design, the concept of sustainability has been addressed by many

(McHarg 1992; Lyle 1994; Van der Ryn and Cowan 1996; Thompson and Sorvig

2000; Birkeland 2002). Measuring sustainability has proved difficult but has been

performed through emergy analysis (Odum 1994; Ulgiati et al. 1994; Brown and

Ulgiati 1997) and the ecological footprint method (Rees and Wackernagel 1996).

Recently, the sustainability of ecoroofs has been measured by emergy (Coffman

and Martin 2004). Coffman and Martin (2004) demonstrated that an agricultural

roof garden can be as sustainable as on-grade gardens and more sustainable

than a conventional residential lawn. However, as useful as a technique like

emergy analysis may be at determining sustainability, it has yet to be accepted

by design professionals and the lay public due to its complex theory. There

continues to be a demand for more distinct performance criteria that define

sustainability.

Several focus groups have been working to define the criteria of a

sustainable landscape: USGBC is developing LEED for Neighborhood

Development (USGBC 2007), and the American Society of Landscape

Architects (ASLA) and the Ladybird Johnson Wildflower Center are developing

11

‘Site Metrics’ to quantify sustainable landscapes as a part of their organizations’

sustainability initiatives (ASLA 2007).

Each group has begun defining criteria that can be used to determine

levels of sustainability. Many of these criteria are related to the concept of

ecosystem benefits, which are the environmental services society receives from

the natural processes of ecosystems (Costanza et al. 1997; Daily 1997; de Groot

et al. 2002). Costanza et al (1997) describe seventeen services and functions

that benefit society, such as: climate regulation, water regulation, nutrient cycling,

and pollination. These services have been shown to be provided in urban

settings by constructed landscapes (Bolund and Hunhammar 1999). These

services are measured using discrete variables that have been developed to

evaluate the performance of a given ecosystem function. For example, the

service of habitat can be assessed as biodiversity and can be measured

discretely by the number of species, or the genetic variation within the examined

species. Equally, regulation can be assessed as water balance and can be

measured discretely by stormwater retention or evapotransporation. Thus, many

sustainable initiatives are now looking at ways to explain and measure

performance through more discrete criteria.

1.3.2 Environmental Services of Vegetated Roof System

The roof systems provide services such as temperature amelioration,

stormwater runoff retention, habitat establishment, and food creation (Peck et al.

1999; Onmura et al. 2001; Scholz-Barth 2001; Brenneisen 2003; Rowe et al.

2003; Wong et al. 2003; Dunnett and Kingsbury 2004; Alcazar and Bass 2005;

12

Hunt and Smith 2005). However, only recently experimental research has been

performed by public institutions. Early experimental research was performed

under proprietary agreements with private sponsors, making dissemination

difficult.

Early research on vegetated roofs focused on developing growing media

to provide services. The growing media used in these systems is called

substrate. Substrates have been designed to optimize water capacity, provide

structure, and limit bulk weight, by being a mix of lightweight mineral and organic

(75% mineral/25% organic material (Hydrotech 2000)) that meet a German

industrial standard. The mineral material is strong, light weight and absorbs water

for slow release; examples include diatomaceous earth, expanded clay or baked

shale. The organic material is hummus or compost, which provides nutrients.

The substrate depth strongly influences the growth and development of the plant

community.

However, public and public-private projects examining more issues are

becoming common (Table 1.1). One example of private sponsorship that initiated

subsequent public research in North America is the Ford Motor Company’s

project. The research was initiated to determine the feasibility of a vegetated roof

system on a new facility in Dearborn, Michigan (USA). Ford partnered with a

roofing manufacturer and a local research institution (Michigan State University).

Initial studies determined an extensive vegetated roof system could be used to

achieve the project’s goals of storm water retention and energy efficiency. An

extensive system of 10 cm depth planted entirely with sedum spp. was installed

13

on a building area of 0.2 Ha. The project evaluated several issues, such as plant

survival in a thin substrate as well as water retention. The research project has

been extended by the local university to determine the survivability of native

perennials and grasses in thin substrates (<15.24cm).

An example of a public project that spurred further research is the Chicago

City Hall, Chicago, Illinois (USA). It is an example of a public retrofit on 3,065m2

of existing rooftop. The project’s main purpose was to initiate studies in the area

temperature amelioration and plant establishment. The subsequent research

questions generated from this project created enough interest to establish two

local centers: the Chicago Center for Green Roof Technology and the Illinois

Environmental Protection Agency Green Roof Research Station. Each center is

studying temperature amelioration, stormwater retention, vegetation and runoff

quality. The establishment of public research appears to growing as more local a

regional communities desire an improved understanding of the environmental

benefits of vegetated roof systems.

14

Name Location Year Est Current Study Focus

North American Centers Pennsylvania State University University Park, PA

USA 2001 Extensive depths, sedum vegetation,

heating, cooling, runoff quality and quantity Michigan State University Lansing, MI USA 2001 Extensive depths, native and sedum

vegetation, runoff quality and quantity, habitat

Green Roof System Consortium Toronto, ON Canada 2002 Extensive and Intensive depths, native and sedum vegetation, garden vegetables, runoff quality and quantity, land use, habitat

Chicago Center For Green Technology

Chicago, IL USA 2003 Extensive depths, sedum vegetation, heating, cooling, runoff quality and quantity

Illinois Environmental Protection Agency

Chicago, IL USA 2003 Extensive depths, sedum vegetation, heating, cooling, runoff quality and quantity

University of Georgia Athens, GA USA 2003 Extensive depths, sedum vegetation, heating, cooling, runoff quality and quantity

British Columbia Institute of Technology

Vancouver, BC Canada

2004 Extensive depths, native and sedum vegetation, heating, cooling, runoff quality and quantity

Lady Bird Johnson Wildflower Center Austin, TX USA 2006 Extensive depths, native and sedum vegetation, heating, cooling, runoff quality and quantity

International Berlin-(Composite by Koehler) Berlin, Germany 1982 Extensive depths, native and sedum

vegetation, runoff quality and quantity, land use, habitat

Augustenborg Botanical Roof Malmo, Sweden 1998 Extensive depths, sedum vegetation, heating, cooling, runoff quality and quantity

Kuleuven University Leuven, Belgium 2000 Extensive depths, slope, sedum vegetation, runoff quality and quantity,

Table 1.1. Green roof research occurring in public institutions

1.4 Specific problems

1.4.1 Current problems in dissemination

Calkins (2005) points out in her study of green building practices that

ecoroofs are a rarely used technology, due to information deficiencies. Her

findings suggest that all green building practices, including ecoroofs, must make

the generation and dissemination of information a top priority in order to become

15

accepted in practice. She states that pursuing detailed, unbiased research on

performance and costs is the key to advancement of all green building practices.

Often created by multidisciplinary teams, ecoroofs can become either

examples of collaboration or underperforming liabilities, due to their critical

technical requirements. Osmundson, in his book Roof Gardens (1999), explains

the very delicate balance between roof garden success and failure. He explains

that, although this is an ancient practice, there is a dearth of current professional

knowledge. Many designers have echoed this concern for a greater clarity, or

understanding, in ecoroof projects (Grant and Jones 2005; Oberlander and

Whitelaw 2005; Dunnett 2006).

Bruce (2005) explains that ecoroof technology cannot persist given the

current paucity of knowledge. This paucity is not only preventing the design

profession from delivering the promised performances of these systems, but it is

also affecting innovation. He states that only limited quantifiable information is

available about the performance and benefits of green roof technology and

argues that continued development must come from both innovation, in the form

of ideas, and technology, in the form of performance. In order to remedy the

problems of information and dissemination, he advocates that “all [ecoroof]

projects serve as a research platform,” which would act “to expand the industry’s

understanding and advocacy of green technologies”. Therefore, collaboration of

design and research through ‘live’ projects is the way to improve knowledge.

This collaboration requires an improved communication in the ecoroof project.

16

Diverse disciplines with specific knowledge and objectives are often

involved in ecoroof design. The engineer is concerned with structural loads and

waterproofing. Additionally, he or she may be interested in stormwater runoff,

storage, or recycling. Environmental scientists are often interested in the issues

of local climate cooling or pollution removal. Both of these professions could be

concerned with the reduced energy uses of the building. Wildlife biologists are

concerned with biodiversity and habitat. Horticulturalists and plant scientists are

concerned with plant survival and maintenance practices. Landscape architects

are concerned with appearance, use, meaning, and general function. Each

disciplinary role influences the responsibilities and outcomes of the other

disciplines, making success largely a result of interdisciplinary coordination.

In addition to a lack of information, language considered specific to the

various disciplines can also impede interdisciplinary projects.

Miscommunications, and the importance of proper communication, are spoken of

by ecoroof professionals (Osmundson 1999; Bruce 2005; Dunnett 2006).

Definitions, concepts, and their associated methods are not equally understood

by all parties, creating miscommunications. In ecoroofs, the language

contributing to miscommunications first begins with the ambiguity in terms used

for ecoroof systems. These miscommunications are passed forward through

design and construction projects, where they can compromise the legitimacy of

post construction research.

17

1.4.2 Current problems in conceptualization

It is difficult to determine the precise causes for the problems occurring in

the conceptualization of ecoroof design, due to the field’s relatively young age

and limited publications. In this section, the contributing effects are described

that individually or collectively create problems between ecoroof design and

research.

For the purposes of this study, a problem can be defined as any specific

matter of difficulty that occurs in a project between design and research

professionals. These problems vary based on the design goals and the type of

the intended research. The problems discussed here may involve various

disciplines, but are specific to the conceptualization of the projects and have

been taken from actual projects. However, the causes of the problems are

commonly found in many projects. It is this study’s intent to illustrate common

contributors, or ‘contributing effects’, to problems in ecoroof design and research,

which, if recognized, would benefit the advancement of the technology and bring

design and research closer together on this subject.

Problems commonly arise between design and research when a design

team strives for synthesis and creates project proposals that are unreasonable

and unsupported, and the outcomes are immeasurable. Often a designer aims

to construct several possible meanings and interpretations within the built work.

This also happens to be the definition of ambiguity. However, ambiguity, in

research is considered a near fatality. It is equivocal and lacks definiteness,

which is contradictory to the overall goal of research.

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When a design proposal expresses contrary positions, it devalues the

research agendas by interrupting the logic with misleading propositions, making it

difficult to prove any results from the design. This often occurs in parts of a

design process that employ inductive reasoning, where ideas are generated from

group interaction. However, the problem is created when the proposal never

passes through a rigorous phase of critique, evaluation, and selection to clear its

contradictory properties. Because contrary positions are so problematic to

research, the design and research of ecoroofs should be scrutinized for problems

possessing contradictions. In this chapter, several ecoroof projects are examined

in terms of contributing effects that lead to contradictions.

Ecoroof problems persist through four contributing effects: ignorance,

generality, complexity, and obscurity (Fig. 1.2). Many problems are created by

ignorance, a lack of knowledge, or what is unknown at the time a design is

conceived. No design is immune to this, especially those that are exploratory, or

first generation. Often, award winning projects that offer important advances to

the field are susceptible to the problems of ignorance.

19

Figure 1.2. The contributing effects persisting in ecoroof projects, shown above

in ovals with arrows indicating cumulative influence.

This issue of ignorance may arise in a project’s original proposal. One

example has been shown in the Gap Corporation building ecoroof (William

McDonough + Partners, Hargreaves & Associates with Rana Creek Consulting).

It was proposed, that employing an indigenous plant palette to the ecoroof would

continue to provide an unaltered form of wildlife habitat conservation. This was

understood as “from a bird’s perspective, nothing has changed” (Burke 2003).

However, the project focused on the technology of growing native plants on

rooftops and the bird research was never performed; therefore the assertion can

20

never be proven, leaving the project open for continual scrutiny. The disregard of

preliminary research demonstrates the effect of ignorance in the

conceptualization of a project.

The failure to communicate the design goals throughout the project is

evidence of another form of ignorance. For example the Ford Assembly Plant

(McDonough and Braungart, Xero flo) in Dearborn, Michigan, was constructed

with the primary intent to reduce stormwater runoff. However, Ford built an

overlook tower where visitors can view the green roof. To meet visitors

expectations of a green “colored” roof, the ecoroof continues to be irrigated past

establishment. This arguably affects the functioning of the environmental benefit

of retention because it was not designed for continued irrigation (Fig 1.3).

Another form of ignorance is when organizational support lacks

knowledge. For example, Leadership in Energy and Environmental Design

(LEED) (a US-based organization renowned for its evaluation system for

sustainable design and construction practices) is currently recognizing ecoroof

designs that possess inherent potential contradictions. In the Mountain Co-Op

project in Winnipeg, Ontario Canada (Design Solutions), a LEED-accredited

building, the ecoroof received a full credit point for ‘habitat’ in the Sustainable

Site section for protecting open space, where it is expected to protect and restore

prairie habitat (Kula 2005). However, it also received points in the Water

Efficiency section for “innovative waste water technology” by incorporating solid

and liquid waste water recycling in the ecoroof, thereby using the ecoroof as a

21

type of biofiltration. It is unknown whether or not these two functions can coexist

without system compromise.

Figure 1.3. An example of the effect of ignorance at Ford Assembly Plant

ecoroof Dearborn MI. Irrigation is used past the plant establishment period in

order to maintain a visual appearance likely impacting its main goal of

stormwater retention (photo by author).

However troublesome, the effects of ignorance are the least concern for

ecoroof projects. A lack of knowledge is always a part of the trial and error

process and subsequent iterations usually overcome ignorance through outside

22

criticism. More worrisome is the level of problems created by the effects of

generality.

A problem created by generality is one in which a project establishes and

retains loose, nonspecific goals that have broad appeal in the design phase, but

which can belabor construction and weaken research objectives. It is assumed

that, during the design process, the design goals will reach greater specificity.

But when imprecise goals such as ‘sustainability’ are proposed early and the

project fails to develop specific objectives, even if considered successful in terms

of budget and waterproofing, the vague agenda can create confusion in design

development and construction and make research objectives difficult to establish.

An example of a project threatened by generality is ”Meadow in the sky”

for the Sechelt Justice Building (Sharp and Diamond) Sechelt, Canada which

replicates an indigenous dry coastal meadow ecosystem in place of the

grassland meadow the building was destroying. The stated design intent was to

fulfill the mission of the firm, which was to “work to restore natural landscapes as

well as establishing new plant communities suited for specific climates” (Sharp

2003). The claim of restoring natural landscapes or creating new plant

communities is so grossly non-specific and contradictory that no form of research

could actually evaluate it. The sub-claim of creating a meadow in the sky pertains

to either the overall characteristics or the unlimited potential of the system, and

both would be extremely difficult to prove. For the designers, researchers, the

client, and the general public, it is difficult to determine whether or not anything is

valuable from such a loose proposal. A project suffering from generality often is

23

received with indifference by both professionals and researchers and could be

overlooked for any beneficial contribution that it possesses.

At the other end of the spectrum from generality is complexity, where

many agendas create a complicated project. The problem of complexity occurs

when numerous agendas are added to a project without consideration of their

effect on the main goals, creating a project predicated upon compromise. It is

understood that overlap occurs in most projects, but that overlap must be clearly

understood and compatible in order to communicate through construction and

possess an environment conducive to research. Any intricate components

should be well developed and expressed.

For example, the Multnomah County building ecoroof (Macdonald

Environmental Planning) experienced a design process in which the original

design concept, created by a visual artist, was replaced because of public

scrutiny, leading to a problem of complexity. The main design goal was to create

an aesthetic public improvement for building occupants and visitors. As the

project lost support, it was coupled to other benefits, such as long term cost

savings, stormwater retention, energy reduction and technical viability. The later

benefits became ultimate priorities, defining by the post construction monitoring,

while aesthetics and social involvement became antidotal and go unmeasured by

researchers. In the end, the ecoroof was constructed with a planting palette

meeting aesthetic demands requiring seasonal irrigation and unexpected

maintenance in the form of weeding, thus compromising sustainable water and

maintenance goals. Limited access occurs on a recessed patio separated by

24

fencing and retaining walls making direct involvement with the plants impossible

and viewing very difficult thus compromising the aesthetic public improvement

goal.

Many projects begin under non-specific general sustainability ideals, but

become problematic through excessively random complexity applied with

generality. In their approach, they obscure the main goals of the design.

Obscurity creates the greatest problem in ecoroof design, because of its impact

on the many parties involved.

Obscurity occurs in a project when so many agendas are added to a

project that the main goals and the foundation knowledge are confounded by

claims that oscillate between very general and complex. The quantity of

contradictions is likely to be higher in projects impacted by obscurity due to a lack

of distinction and the occurrence of periodic confusion. Projects of obscurity can

be identified by these contradictions that propose almost everything, while failing

both to explain how they will deliver and to prove what is being proposed.

For example, the plan called “Long Island (Green) City,” (Balmori

Associates) proposed to create an elevated Central Park in Queens, New York

(Wayland-Smith 2005). Their claims are so exhaustive and unclear that the

design proposal contains several contradictions. The claims are illogical,

confusing, and concealed. Overall, they claim to provide sustainability outcomes

while ignoring universally accepted ecological processes and demonstrated

results from ecoroof research. Lastly, they claim to be providing a pre-accepted

aesthetic of nature that is based on a grid layout.

25

Balmori Associates envisions a “self-sufficient and self-sustaining” system

that brings “nature’s principles of reuse, storage and adaptability” into the city for

the contemplation of our coexistence with nature, through “checker board,” or

“Mondrian-inspired” geometric grids that displace the current “ecological

experiments” of ecoroofs (Wayland-Smith 2005). This proposal contradicts itself

numerous times by misrepresenting how it will function; its most obvious

contradiction is the antithetic proposal of establishing a permanent visual field, or

scene, while operating within ecological theory and promising a self-sufficient

system. There are two major contradictions in this proposal. First, the proposed

aesthetic contradicts ecological understanding. The Sedum spp. palette is

governed by physical laws of energy and will function to reorganize the “checker

board” design creating a patchwork aesthetic, which has been shown by Kohler

(2003). Even the thinnest substrates created for Sedum spp. can recruit

colonizing grasses and herbaceous species (Koehler 2003; Dunnett 2005). In

order to maintain the grid and its associated aesthetic, the system would require

weeding and fertilization, as demonstrated by Emilsson (2004) and Rowe et al

(2006) even in the extremely thin substrates. Secondly, Wayland-Smith (2005)

goes on only when these aesthetically driven systems replace the current

“ecological experiments” of ecoroofs will there be a “wide spread adoption of the

technology” . This very large contradiction is the claim that the technology is

functional understood and no more experimentation (or innovation) is needed,

which defies the opinions of most designers and researchers (Miller 2004; Bruce

26

2005; Calkins 2005; Grant and Jones 2005; Oberlander and Whitelaw 2005;

Dunnett 2006).

1.5 Proposed Methodology

1.5.1 The design model precedent

The issue of collaboration of research and design is contested by many

designers, with regards to when research is to be included in the process, the

types of expected results, and even semantics (Chenoweth 1992; LaGro 1999).

However, models of how designers can incorporate research into a design

problem do exist (Milburn and Brown 2003). And examples of ecoroof projects

employing a design-science method have been recorded (MacDonagh et al.

2006).

Milburn and Brown (2003) describe a design model that parallels the

scientific method of theory-hypothesis-experiment-evaluate, but allows for

creativity and collaboration. It is particularly well suited for complex processes.

They describe it as the Complex Intellectual Activity model, which is a didactic

approach that defines a process where standard rules are applied, specific data

are analyzed, and new ideas are developed and tested. This model begins by

collecting preliminary information from generalized understandings (theory) and

previous studies (published findings); the problem is broken down into elements;

the information is accessed, analyzed, and applied to elements of the design

which are synthesized to create a coherent design or plan (proposal); and results

(new findings) are evaluated and stored for future use. Milburn and Brown go on

27

to explain, through what they call an analytical approach, that research is

continual and informs the design; that the process is pragmatic; that the concept

is interpreted on the site and the site remains significant where the overall focus

in on the process. This allows creative problem solving and experimentation to

be governed by a process that delivers measurable results. The complex

intellectual activity model proposed by Milburn and Brown was slightly modified

for its application by adding a stage of assessment (Fig. 1.4). Also, descriptions

of activities were clarified to include both the research scientist, as well as, the

designer.

Figure 1.4. The complex intellectual design-research model allows research and

design collaboration through semi-alternating phases. The model begins with

current knowledge that can be applied to the site and defined through discrete

elements that can be constructed, assessed and disseminated. The knowledge

returns to inform future projects.

28

1.6 Design-Research Domains

The design-research domains established from scientific areas in order to

assist designers in advancing design concepts targeting environmental service

goals. The domains are ‘tools’ used by designers to enhance the communication

in the conceptualization of projects which subsequently allows for the improved

potential of dissemination. The domains focus communication and link the

design process with post-construction evaluation opportunities through

measurable criteria. The presence of criteria can then engage research

assessment, evaluation and dissemination.

These domains are not mutually exclusive per se, but are categorized to

direct the project towards various measurable criteria (Fig. 1.5). They are based

on structure-function relationships in which each domain can influence the

others. For example, productivity might influence biodiversity. The general idea

is that first a domain is identified as the main project goal and then the

performance criterion can be identified. Subsequent domains can then be

selected. The domains are as follows: productivity, biodiversity, energy balance,

nutrient cycling, hydrological cycling, and stewardship.

Each listed domain, is presented based on published information for that

domain. In this way, each domain provides a short literature review of previous

findings.

29

Figure 1.5. A diagram of ecoroof design-research domains with example criteria

are shown in circles and two-way arrows indicate potential influence.

1.6.1 Productivity Domain

This domain includes the growth of plants (possibly animals) and overall

production of biomass as a baseline measure of ecoroof function. Projects

concerned with producing vegetative cover, or developing biomass as a form of

mitigation, are concerned with overall function which is indicated by the level of

30

productivity. Productivity is the rate of production of biomass of an ecosystem

and provides a general view of how an ecosystem performs (Stiling 2002).

Primary productivity, the growth of plant biomass, is the basic measure and is

usually recorded in g.m-2.yr, Productivity underlies various goals of sustainability,

wherein the level of productivity correlates to levels of ecosystem function. For

example, high productivity is commonly associated with higher nutrient uptake,

water uptake, and solar interception (Lieth 1978). For design projects striving for

higher ecosystem benefits higher productivity would be the priority design intent.

Although productivity has not been identified as a sustainability goal in ecoroofs,

it is discussed here because it is a composite measure that can be associated

with many ecosystem services.

In recent ecoroof studies, productivity has been concerned mostly with the

individual plant and to a small degree the ecosystem. In ecoroofs studies, whole

plant level studies on establishment, survival, and growth are most common, as

roof designers attempt to create a plant palette that will survive the conditions of

the roof. It has been found that ecoroof plant growth is influenced by 1) the water

capacity of the system, 2) the method of plant implementation, 3) the building

architecture, and 4) the maintenance of the vegetation stand (Koehler 2003).

Koehler (2003) has compiled information and drawn conclusions from

eight separate study sites that have recorded data over an eighteen-year period

of collection. He states that total plant biomass (dry weight) from these studies

ranged between 4.2 g.m-2.yr and 47.2 g.m-2.yr. The leaf area index is 0.64 on the

31

highest area of coverage. And the shoot to root ratio is approximately 0.9. This

information was supported by his earlier studies (Koehler 1990).

In both studies by Koehler (1990 & 2003), dominant species are listed and

given as a percent of cover. He states that Allium schoenoprasum had more than

75% coverage in the first site; the second site, a younger site, was covered with

60% Sedum spp. The younger site possessed a greater number of plant species

(88) compared with the older site, but it was noted that this site originally used

irrigation in establishment methods. None of the other species’ percentage of

cover were given. Although no quantities or percentage of cover were listed,

Koehler states that the total number of plants in the older site has declined with

age. Also, absent from the recorded data was the listing of substrate depths and

maintenance regimes.

In general, green roof ecosystems are oligotrophic, or low nutrient,

because they rely solely on precipitation for nutrient input. Low soil water content

is stated to be a factor limiting green roof plant growth. Pearce (2003) records

observations that support this, while Koehler’s (2003) study concludes that green

roof plants will develop slower than plants on typical grasslands due to

physiologic constraints of the ecosystem.

The substrate parallels the properties of an A-C soil horizon structure,

where a plant exists in a small amount of soil over immediate bedrock preventing

its connection with any base-flow water source. This makes the plant entirely

dependent on precipitation as a water source. Koehler (2003) cites that plants in

32

central Europe must be able to adapt to up to four weeks without water during

their summer growing periods.

Species lists for North American projects are becoming more available.

However, they do not always distinguish the type of roof properties that would

provide the appropriate habitat. Native plant development is the subject of

experiments in various locations (see Biodiversity domain). The most commonly

used plants are Sedum spp., due to their tolerance of extreme environmental

conditions.

The growing of vegetable garden plants has been documented in texts

(Tinkel 1977) (Kortright 2001; Levenston 2002). Practical planting and growing

methods are covered by Tinkle (1977). Rough data on the quantities of food

produced has been recorded, but they are not supported by detailed explanation

of methods (Ehrenfeld 2000; Martin 2001).

As the priority for providing ecosystem benefits persists in ecoroofs,

productivity is likely to emerge as a more important determinant influencing

design intent. It may also become a strong delimiter for the classes or types of

ecoroof systems.

1.6.2 Biodiversity Domain

This domain includes the variation in plant and animal life found on an

ecoroof. Projects involving habitat goals, biological diversity, or species

mitigation are concerned with biodiversity. Overall habitat functions to conserve

important biological and genetic attributes, and evolutionary processes can be

measured through diversity. Biodiversity can be defined as any one of the

33

following: the variety of species (species diversity), genetic variability among

individuals (genetic diversity), and variety of ecosystems (ecosystem diversity)

(Miller 1998). This offers potential for flexibility in the design of an ecoroof for

habitat. For example, if biodiversity is a goal of the project, then a criterion could

be plant species richness (the number of plant species).

Biodiversity in green roofs thus far has addressed species and ecosystem

level issues and is considered to have enormous opportunities for more research

(Lundholm 2005). Moreover, creating habitat for species conservation has been

the primary reason behind recent initiatives within this area, in an effort to

improve regionally-based species diversity (Gedge 2003; Brenneisen 2005).

General habitat for maximum species biodiversity is now advocated and

technically instructed at the annual Greening Rooftops for Sustainable

Communities conference.

The work to date has dealt largely with secondary biodiversity (fauna) and

its connection with primary biodiversity (plants) at the species level. Secondary

biodiversity has been examined by Brenneisen (2001, 2003) and Kadas (2002). It

has been shown that invertebrate species diversity (Shannon Index) and roof

design factors such as substrate depth, structure, and vegetation diversity are

strongly associated (Kadas 2002). Bird, beetle and spider diversity (species

richness) correlated with roofs possessing topographic (mounds), substrate, and

floristic diversity (Brenneisen 2003). Invertebrate community composition has

been listed for central North America (Coffman and Davis 2005) and assessed

for rare species in England and Switzerland (Jones 2002; Brenneisen 2003).

34

Green roof fauna communities have been compared to terrestrial

brownfields with differing results. Brenneisen (2003) found community similarity

across selected taxa (birds, beetles and spiders), while Kadas (2002) recording

single taxa (spiders) did not.

Rare species of fauna and flora have been documented in green roofs.

Invertebrate species have been the most commonly assessed fauna.

Brenneisen (2003) found four spider species, and twenty four beetle species

listed in the Red Data book. In England, Kadas (2002) recorded two rare spider

species, and Jones (2002) recorded rare bug species and several nationally

scarce beetles and spiders.

One species of bird, the Black Redstart (Phoenicurus ochruros) was found

in high abundance in vegetated roofs in Switzerland. This bird is an endangered

species in the United Kingdom. As a result of a community action plan creating

15,000 m2 of green roof in London, the Black Redstart has been observed using

the new roofs (Gedge 2003).

Rare species of plants have been recorded on the Moos water treatment

plant in Zurich, Switzerland. The roof was constructed in 1914 using a traditional

method of placing the existing soil on the building rooftop, and it continues to

exist today without replacement or disturbance. The topsoil was taken from the

local environment, which at the time was a seasonal wet prairie. Consequently,

the green roof possesses numerous extirpated plants, including several rare

species and nine species of orchid (Orchis spp.) It is home to the only population

of Orchis moro left in the region (6000 individuals).

35

A few studies draw attention to the ecosystem level diversity by

recognizing the importance of the substrate (Brenneisen 2004; Dunnett and

Kingsbury 2004). The ecosystem most commonly associated with ecoroofs is the

rock outcrop ecosystem, which is a thin topsoil layer over parent material

possessing an A-C horizon. This is where native plant palettes have been

generated (MacDonagh et al. 2006) and plant community research studies are

based (Lundholm 2005).

Survivorship for native plant experiments are being performed by Michigan

State University and case study observations are found on locally generated

public projects. Although it is the intention in many of these projects that native

plants are used, they must use plants that can adapt to drier, more extreme

conditions. Survivorship can be confounded when non-adaptive native or

horticultural species are selected and supplemental irrigation becomes a post-

hoc management practice.

1.6.3 Energy

The energy domain includes all forms of energy used or altered by an

ecoroof. Projects involving resource use and temperature analysis, such as the

urban heat island effect, are concerned with energy. Ecoroof influence on the

urban heat island effect has been studied at local as well as regional scales, and

is currently a part of the Smart Growth and Urban Heat Island initiative by the US

Environmental Protection Agency.

Vegetated roofs have been modeled to reduce roof surface and ambient

air temperatures (Palomo Del Barrio 1998). In experimental studies, roof

36

maximum surface temperatures have been reported to be reduced on green

roofs by approximately 30o C (Onmura et al. 2001; Liu and Baskaran 2003; Tan

et al. 2003; Wong et al. 2003). Membrane temperatures between conventional

exposed roofs and green roofs differ by 40o C (Liu and Baskaran 2003). More

convincingly, heat flux was reduced by 50% in Onmura’s study, and Liu and

Baskaran (2003) saw diurnal fluctuations of 45 o C for a conventional roof while

recording only 6 o C in a vegetated roof. Tan et al (2003) reported similar

findings.

The average daily energy demand for space conditioning due to the heat

flow through a conventional roof was 6.0-7.5 kWh·day-1 (20,500-25,600 BTU·day-

1). However, the growing medium and the plants of the green roof modified the

heat flow and reduced the average daily energy demand to less than 1.5

kWh·day-1 (5,100 BTU·day-1)–a reduction of over 75% (April-Sept) (Liu and

Baskaran 2003). Multi-story buildings in warm summer climates have been

shown to reduce up to 6% of summer energy costs (Alcazar and Bass 2005).

Martens and Bass (2006) calculated energy savings in a 250m x 250m green-

roof design with 50,000 W internal loading. The seasonal energy savings was

found to be 73%, 29%, and 18%, for a 1, 2, and 3-story design, respectively,

using the Bowen ratio and ESP-r model.

Energy modeling has been used to accurately simulate green roof

temperature cycles by Gaffin et al. (2006). They found a range for the Bowen

ratio β of 0.12 –0.35, indicating the latent heat losses (evapotranspiration) were a

factor of 3-8 times larger than sensible heat (air convection). The variations in β

37

were evidently due to variations in soil moisture content. On a regional scale,

modeling of the urban heat island effect with irrigated green roofs has been

estimated to reduce the urban heat island by 1oC (Bass et al. 2003).

1.6.4 Nutrient Cycling Domain

The nutrient cycling domain includes the recycling of chemical elements

that are used to support life, which in excess can contribute to waste. Projects

concerned with water quality, carbon sequestration and soil fertility are

concerned with nutrient cycling. Because nutrients are the chemical elements

that are used to support life they are commonly tied to energy issues because

they help facilitate energy flow. Some of the most common are hydrogen, carbon,

oxygen, nitrogen, and phosphorus. Water and light (energy) are also essential

nutrients, but here they have their own domains for clarity. The quantities of

these common elements are often studied to understand how a system is

functioning. For example, nitrogen levels can be assessed in plants and the soil

to determine how nitrogen is moving through the ecosystem. Balanced nitrogen

levels in a system means the nutrient is being used efficiently for plant growth,

but excess amounts found in the soil can create change in the plant community.

New species that require more nitrogen to survive will begin to establish. Or, the

excess nitrogen could be carried out of the system by water leading to an

accumulation in another ecosystem. This creates pollution.

Nutrients are studied by assessing their quantities in water, soils and

organisms (plants and animals). The most common study is soil nutrient

assessment used to determine nutrient availability (usually called fertility), such

38

as the amount of phosphorus to grow fruit crops. More complex studies look at

the cycles through food web patterns and organism effects on nutrients. These

can address local cycles, such as the local uptake of phosphorus by plant, or

global cycles, such as carbon cycle influence on the biosphere.

Nutrient cycling has not been largely investigated in ecoroofs, but is

emerging in the USA in order to address National Pollutant Discharge Elimination

System Phase II (NPDES) (www.epa.gov) requirements to reduce stormwater

impacts on receiving water bodies. The published results for ecoroof effect on the

nutrient levels in stormwater discharge have been shown to be contradictory.

The nutrient inputs come from three sources: the initial substrate,

maintenance practices and atmospheric deposition. The methods for measuring

nutrients in the hydrologic cycle have been through direct discharge points from

the ecoroofs as well as in receiving bodies of water (Koehler 2003).

Ecoroofs have been shown to reduce lead 94.7%, cadmium 87.6% and

nitrate 80.2% to receiving waters (Koehler et al. 2002). Beattie et al. (2002) has

preliminary shown reductions in first flush and composite events from

precipitation values in nitrate (50%), and total suspended solids. Turbidity

showed an increase while electrical conductivity results were inconclusive.

However, some fluctuations appear to be a result of maintenance and use on the

green roof (Hutchinson et al. 2003; Lipton and Strecker 2003).

It has been demonstrated that fertilization allows for exportation of

nutrients, even when applied at the rate of the international guidelines for green

roofs (FLL) (Emilsson 2004). In preliminary findings, Emilsson (2004) found that

39

by applying the FLL guidelines of 5g(N)·m²·yr-1) produce a 16% rise in nitrogen

export. Recordings of specific levels of nutrient application and use of time-

released products reduce nutrient export (Rowe et al. 2006). However, a study

by Hunt and Smith (2005) indicated that newly constructed green roofs leach

nitrogen (Total Kjeldahl Nitrogen, NO3+NO2, NH3) and phosphorus (Total

Phosphorus and Organic Phosphorus) from their substrate when compared to

rainfall and a control roof. Subsequent studies showed that this could be due to

the amount and type of compost used in the substrate (Hunt et al. 2006).

1.6.5 Hydrologic Cycle Domain

The hydrologic cycle domain includes the use of water by an ecoroof and

its subsequent impact on nearby environments. Projects involved with

stormwater retention, irrigation and grey water recycling are concerned with

hydrologic cycling. The hydrologic properties are one of the more studied areas

of vegetated roof system technology. Most studies have focused on water

quantity through the system as retention and runoff. This is one reason green

roofs have achieved recent popularity. As stormwater runoff has been linked to

flooding and combined sewer overflow events, ecoroofs have been assessed for

reducing roof runoff.

The hydrological cycle is important in urbanization for the reason of

flooding. However, it is equally important for its influence on living things. The

amount of available water influences vegetation and animal life.

Generally, vegetated roof systems retain between 20-80% of annual

rainfall in temperate climates (Mentens et al. 2003) and can reduce peak flows

40

(Hutchinson et al. 2003; Rowe et al. 2003). Studies in Berlin have recorded

runoff reduction of 75% of total precipitation (Peck et al. 1999). Koehler (2002)

also references a Berlin study that estimates total (annual) runoff reduction to be

60-79% over a three year period. However, the substrate depth was not

mentioned. Hutchinson et al. (2003) has recorded local data for Portland, OR

stating 4-5 in (12 cm) thick can absorb 69% of the rain falling on to it. This is

assumed to be annual data for that region. Additionally, a fourteen inch deep

intensive green roof is said to reduce annual runoff by 85-95% (Miller 2002).

Minke (1982) has been quoted by Peck (1999) stating that a simple grass

covered roof with 20-40 cm (8-16”) deep substrate can hold 10-15cm (4-6”) of

water. Peck (1999) interprets Liesecke’s (1989) work to conclude that retention

rates vary with seasonality, stating that summer rates are 70-100%, while winter

rates are 40-50%.

Storm events contribute another set of data that appears to show green

roofs, especially extensive green roofs, are effective at retaining short duration

storm events such as cloud bursts. A winter ten year storm event records only a

43% retention, but summer storm event retentions were recorded to be 100% for

the same 8 cm (3.5 inch) deep green roof (Miller 2002).

Beattie et al. (2002) at the Penn State Center for Green Roof Research, in

a web-published EPA study, recorded runoff reductions of small duration storm of

approximate 50%. Rowe et al (2003) has recorded reductions of 74% for a 4 cm

deep, 2% sloped roof, and 69% for a 4 cm, 6.5% sloped roof over a 6 week

study. However, these occurred at very low levels of precipitation. In a low-

41

volume storm event (10cm), a green roof reduces runoff 80%, while in a large

storm event (30cm), the same green roof reduces runoff to no more than 20%

(Green Roof Consortium 2003). Similar results were recorded by Rowe (2003).

Miller (2002) has calculated that greater depth of substrate can improve

retention capacity. He calculates that a typical 35 cm (14”) deep green roof can

retain up to 95% of annual rainfall (Miller 2002), and can be used in combination

with other water management techniques to obtain a zero discharge goal for the

site.

Graham and Kim (2003) use modeling to analyze the effect of green roofs

in combination with other point source control strategies, such as bioretention.

This incorporates land use variations into an overall analysis. Projections from a

multi-family lot with 70% lot coverage show runoff reductions by 80% in dry year

to 40% in a wet year. However, this model shows that annual runoff reductions

correlate with soil depth, but do not change under intense storm events (Graham

and Kim 2003).

Carter and Rasmusen (2005) calculated a runoff (hydrologic) curve

number (CN) of 88 for an extensive green roof from experimental studies using

the Soil Conservation Service model. From their study they found that ecoroofs

were shown to be most effective on small storm events at the roof scale. For

example, they found in a watershed in which ecoroofs maintain 15% of the total

land area and 30% of the total impervious area, the ecoroofs create a 15%

reduction in stormwater volume from the 1.2” storm event, 7% reduction for the 1

year, 24-hour event, 4% reduction for the 25 year, 24-hour event, and 3% for the

42

100 year 24-hour event. The also found ecoroofs alone were not effective

enough to protect for urban discharges into receiving streams in suburbanizing

watersheds, thus recommending they be included only as a part of watershed

scale management.

Another way of understanding the hydrological properties of vegetated

roof systems is to determine the maximum water capacity (MWC) which is a

benchmark number for the amount of water that can be stored in the ecoroof

system (Miller 2002). By subtracting the quantity of water absorbed by the

system during a rainfall event that will not be released later as runoff, which is

known as field capacity, from the MWC, the effectiveness of suppressing peak

flows can be determined. When this involves the design, it is measured as the

initial abstraction, which is the quantity of rainfall that must occur before

appreciable runoff will commence. By designing vegetated roof systems that

have a higher initial abstraction, a greater reduction in runoff is created. Miller

(2003) states that water management is determined by substrate, drainage layer

and irrigation. The substrate should efficiently absorb and retain water, be readily

drained, and offer a high void ratio (air volume) (Miller 2003).

Results from a study by Menten’s (2003) show green roof performance is

determined by four basic factors: roof properties (slope, substrate depth, etc)

and yearly, seasonally, and storm event properties. He gives the example for

annual reduction in Brussels: standard roof obtains 19% reduction, standard with

5 cm of gravel obtains 23% reduction, green roof with 5cm of substrate obtains

50% reduction, green roof with 10 cm of substrate obtains 55% reduction, and

43

green roof with 15 cm of substrate obtains 60% reduction (Mentens et al. 2003).

It is generally understood that green roofs reduce stormwater, but its

performance varies. Menten’s four factors may explain the inconsistency of

findings in the literature.

Solutions for addressing design intents with water quantity and quality

may mean coupling ecoroofs with other integrated management practices. As

previously stated, Carter and Rasmussen (2005) showed that ecoroofs would not

be enough to reduce flows to receiving streams in an urbanizing watershed and

suggest bioretention in the form of rain gardens as an integrated practice that

may achieve on-site retention.

Lastly, hydrology has begun to be measured using the evapotranspiration

of ecoroofs by Schmidt (2006). In preliminary studies, he showed ecoroofs

evapotranspired over 60% of their water budget. Using lysimeters, he is

investigating the potential and real evapotranspiration rates for building cooling

effect. Compton and Whitlow (2006) have linked evapotranspiration to

stormwater retention.

1.6.6 Social Understanding and Stewardship

The social understanding and stewardship domain includes the

contribution and impact of ecoroofs directly on the lives of people. Projects

involving education mission or scenic improvements are concerned with social

understanding and stewardship. This domain is largely implied through

experiential and aesthetic functions, and supported mostly by observation rather

than empirical research. It is often essential to have some type of direct human

44

benefit when designing an ecoroof: therefore, work in this domain addresses

those design intents made for direct involvement, or engagement, of people with

ecoroofs.

The experiential functions of ecoroofs, as roof gardens, has been

presented by Tinkle (1977), Osmundson (1998), and Dunnett and Kingsbury

(2005) under the same general arguments as parks, or on-grade gardens. They

function as leisure and recreation spaces in public settings, often substituting for

a park when on-grade space is not available (Dunnett and Kingsbury 2004),

while in private they offer opportunities for respite and isolation where visitors

experience “pleased astonishment that such a nice, quiet place can exist in a

busy city” (Osmundson 1999). If created informally by a resident or group, they

provide opportunities for individual exploration, creativity and ownership (Tinkel

1977).

Consideration within this domain, especially when designing an intensive

ecoroof, opens the project to a wide range of design intents common to park and

residential landscape designs. This can make outcome criteria difficult to

determine as design programs can be developed to include anything from

passive to active recreational activities, and can be changed rapidly in the design

process.

Aesthetic improvement as one of the functions of ecoroof design is

generally accepted as a given; therefore, there is a dearth of empirical

information in this area and only a few published opinions. It is assumed that

people prefer a view of a green roof to that of a conventional roof based on the

45

history of park and garden construction which is implied by Peck et al (1999).

From this general assumption, critiques are forming to address context,

biodiversity, and visual quality, where aesthetics can be used to convey cultural

and historical references (Oberlander and Whitelaw 2005; Wayland-Smith 2005;

Dunnett 2006). A method for quantifying the scenic improvements of roof

greening has been explored by Lee and Koshimiz (Lee and Koshimiz 2006).

Educational missions in this domain are very common. Many first-time

public projects in a city are considered to be demonstration projects. However,

organizations fail to determine any performance criteria of the demonstration and

convert that information to published results. It is likely that they are highly

effective, but failure in the educational mission’s to specify evaluative criteria

relegates the project to support only through personal testimonials or critiques.

1.7 Sample Applications

Three projects were selected to be fitted with design-research domains to

demonstrate the use of the methodology to improve clarity and communication in

the technology. These projects are not known to have been designed or

constructed using design-research domains, but possess the coordination

needed between design and research objectives. For these projects, the fitted

domains were selected based on each project’s goals and operation. The

selection of more than one domain creates a network which highlights the

projects’ priorities, and influences of one domain upon another. To illustrate the

use of design-domains each project is represented in an image-diagram (Figure

46

1.6, 1.7, and 1.8). These image-diagrams are used to synthesize the various

issues into one image that can be approached equally by different disciplines.

1.7.1 Rosetti Building

The Rosetti Building ecoroof in Zurich Switzerland is designed to provide

habitat for local wildlife while generally improving the ecological design of the

building. The design intent is to recruit an invertebrate community similar to that

found in local river-gravel bar systems by providing similar plant species and soil

conditions. Therefore, the project operates primarily in the domains of

biodiversity and secondarily in hydrologic cycle, energy and productivity

(Fig.1.6).To meet these biodiversity goals, the ecoroof uses local soils in

mounded hummocks (38.1cm) to increase plant diversity, and exposed river

cobbles in flat areas (7.6cm) to improve invertebrate diversity. The plant and

insect communities are measured by species richness. The hummocks allow for

vegetative patchiness (50% cover in year 1), while exposed cobble areas provide

necessary habitat for targeted spiders and beetles species. The patchiness

means lower percentage of vegetative cover. This reduces the value, to a small

degree, of the hydrological and energy performance objectives. The design-

research team did not clarify any intent in this area, but specifically addressed

productivity by specifying a substrate mix composed largely of inorganic

materials to match the soils of a gravel bar. Therefore, it is by default at least a

secondary priority. The planting was by seed and the plant community will self-

organize with the developing invertebrate community (70% cover projected by

year 10). Conceptual Design by Jaques Herzog & Pierre De Meuron and

47

Stephan Brenneisen, Post construction research by Stephan Brenneisen, PhD.

Constructed 1998.

Figure 1.6. An illustrative image-diagram for the Rosetti Building ecoroof in

Zurich, Switzerland prioritizing biodiversity, productivity, energy, and hydrologic

cycling (shown in circles) in the project agenda. The background image shows

the site while text explains the proposal, means of installation and assessment

criteria.

48

1.7.2 Ford Assembly Plant Ecoroof

The Ford Assembly Plant Ecoroof, Dearborn, MI USA, is designed to

provide energy savings and reduce stormwater runoff in order to lower the

construction and operational costs of the building, in an effort towards a more

environmentally responsible industry. Therefore, the project operates primarily in

the domains of hydrologic cycle and energy and secondarily in the domains of

stewardship and biodiversity (Fig. 1.7). The ecoroof uses engineered substrate

and exotic sedum plant palette to achieve these goals. The substrate is >7.6cm

deep and consists of expanded slate, sand compost and peat. The design

process incorporated an intermediate comparative plot experiment run by

researchers at Michigan State University to select the proper system. In this step,

the system was evaluated for performance and modeled for energy and

stormwater retention on the building. Goals of wildlife habitat creation and public

education subsequently evolved. The Ford Company built an overlook for the

ecoroof which is open for public tours and has examined the fauna on its roof.

Conceptual design by William McDonough + Partners, Design development and

initial replicated plot experiment by Michigan State University, detailed design by

Xero Flor, and Post construction research is monitored by Don Russell.

Constructed 2002.

49

Figure 1.7. An illustrative image-diagram for the Ford Assembly Plant Ecoroof,

Dearborn, MI USA prioritizing energy, hydrologic cycling and stewardship

(shown in circles) in the project agenda The background image shows the site

while text explains the proposal, means of installation and assessment criteria.

1.7.3 Latter Day Saints Conference Center

Church of Latter Day Saints Conference Center ecoroof, Salt Lake City, UT,

USA, was designed to recall the story of the church leaders’ religious journey

taken in the unique environmental settings through the replication of several local

ecosystems (Fig. 1.7 ). The intent was to communicate the interactions between

50

religion and place through personal experience. Therefore, the ecoroof operates

primarily within the domain of stewardship and secondarily in the domains of

biodiversity and energy. It is an intensive roof garden for church members and

visitors where access to the roof garden is provided year round. The use of water

as a design element is fundamental to the narrative where it represent numerous

episodes in the story of the church, while creating place. Overall, it represents

spirit, energy, and knowledge that flows in the world. It functions secondarily to

promote biodiversity by recognizing ecosystem diversity as valuable. Lastly, the

use of vegetation and water in the roof garden cools the immediate surroundings.

Conceptual Design by Olin Partnership. Post construction research by LDS staff.

51

Figure 1.8. An illustrative image-diagram for the Church of Latter Day Saints

Conference Center ecoroof, Salt Lake City, UT USA prioritizing stewardship,

biodiversity and energy (shown in circles) in the project agenda. The images

show the site while text explains the proposal, means of installation and

assessment criteria.

52

1.8 Discussion

The problem of communication and the contributing effects raise a

cautionary flag for designers, such as landscape architects, who intend to lead

ecoroof projects with aesthetics-only design proposals, as championed by Kiers

(2004) and Wayland Smith (2005). This strategy may result in a compromise in

performance. Instead, aesthetics or experiential goals should be strongly

balanced with science, as shown by MacDonagh et al (2006). New aesthetics in

vegetated roofs systems may be explored with ecoroof experimentation, but it

should not compromise or contradict understood performance. A reliance solely

on visual information is likely to marginalize the designer’s leadership role.

The design-research domains may contribute to the design decision

framework proposed by Grant and Jones (2005) . However, at least three issues

must be considered when using their framework. One is that the biological

factors must be included as criteria (both plants and animals), because research

findings have shown that plants affect ecoroof performance. Second, design

cannot entirely rely on pure research experimentation, but must work hand-and-

hand to develop innovative technology through applied research and post

construction evaluations. Lastly, it is a precedent based framework relying on

current knowledge through case study review and not on scientific findings. This

isolates new design from research endeavors and diminishes the legitimacy of

research findings.

The fields of design and scientific research are unlikely to move towards

adopting a common methodology, yet the coupling of disciplinary methods

53

seems plausible. Landscape architectural firms have merged with researchers in

order to approach environmental problems from both disciplines (Arvidson 2004).

Arvidson (2004) explains the ‘merging’ leads to a longer ‘design-science’ process

because it tends to be additive from both disciplines. If this, in fact, becomes the

common form of disciplinary interaction, then researchers must improve their

understanding of the design process. Subsequent studies should be performed

to investigate issues and explain to researchers the factors in the design process

that may affect research. With this improved understanding by research it is likely

both disciplines can better communicate to assist individual projects, as well as,

the technology.

The advancement towards determining sustainability by the criteria of an

ecosystems services model is likely to assist ecoroof projects. Designers and

researchers may find common ground for discussion, and from their interaction

may emerge a clarification of the ambiguous term “green.”

54

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Arvidson, A. R. (2004). " Deeper shade of green: three firms strive to fuse design

with ecology." Landscape Architecture 94(3): p.46,48,50,52-56. ASLA. (2007). "Site Metric Summit." Bass, B., E. S. Krayenhoff, A. Martilli, R. B. Stull and H. Auld (2003). The impact

of Green Roofs on Toronto's Urban Heat Island. Greening Rooftops for Sutainable Communities, Chicago. Green Roofs for Healthy Cities.

Birkeland, J. (2002). Design for sustainability: A sourcebook of integrated, eco-

logical solutions. London ; Sterling, VA, Earthscan Publications. Bolund, P. and S. Hunhammar (1999). "Ecosystem services in urban areas."

Ecological Economics 29(2): 293 - 301. Brenneisen, S. (2003). Biodiversity of European Greenroofs. In conference

proceedings of Greening Rooftops for Sustainable Communities Chicago, IL, Green Roofs for Healthy Cities.

Brenneisen, S. (2004). From Biodiversity to Agricultural Productivity. In

conference proceedings of Greening Rooftops for Sustainable Communities Portland, OR, Green Roofs for Healthy Cities.

Brenneisen, S. (2005). Green roofs recapturing urban spaces for wildlife- A

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Bruce, J. (2005). The weakest link: Constructing green roofs in the real world. In conference proceedings of Greening Rooftops for Sustainable Communities Washington D.C., Green Roofs for Healthy Cities.

Burke, K. (2003). Green roofs and regenerative design strategies-The Gap's 901 Cherry project. In conference proceedings of Greening Rooftops for Sustainable Communities, Chicago, IL. Green Roofs for Healthy Cities.

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landscape architecture." Landscape and Urban planning 73(1): 29-48. Chenoweth, R. (1992). "Research: hype and reality." Landscape Architecture

82(3): 47-48. Coffman, R. and G. Davis (2005). Insect and Avian Fauna Presence on the Ford

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http://www.greenroofsystems.org. Costanza, R., R. d'Arge, R. de Groot, S, S. Farber, M. Grasso, B. Hannon, K.

Limburg, S. Naeem, R. O'Neill, J. Paruelo, R. Raskin and P. Sutton (1997). "The value of the world's ecosystem services and natural capital." Nature 387(6630): 253-260.

Daily, G. C., Ed. (1997). Nature's Services: Societal Dependence on Natural

Ecosystems. Washington D.C., Island Press. de Groot, R. S., M. A. Wilson and R. M. J. Boumans (2002). "A typology for the

classification, description and valuation of ecosystem functions, goods and services." Ecological Economics 41: 393 - 408.

Dunnett, N. (2005). Vegetation composition and structure significantly influence

green roof performance. In conference proceedings of Greening Rooftops for Sustainable Communities Washington DC.

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Dunnett, N. (2006). Green roofs for biodiversity: Reconciling aesthetics with ecology. In conference proceedings of Greening Rooftops for Sustainable Communities Boston, MA.

Dunnett, N. and N. Kingsbury (2004). Planting Green Roofs and Living Walls. Portland, OR, Timber Press.

Dunnett, N. and N. Kingsbury (2004). Planting Green Roofs and Living Walls.

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CHAPTER 2

PRIMARY PRODUCTIVITY, WATER RETENTION AND LEACHATE QUALITY

IN TWO ALTERNATIVE ECOROOF DESIGNS

2.1 Abstract

This study is intended to provide environmental scientists and planting

designers with an understanding of the environmental performance of vegetated

roof systems. It describes the results of an experiment evaluating the net primary

productivity, water retention and water quality of two ecoroof designs when

compared with conventional ecoroof designs. The investigations accessed the

effects of class, alternative and plant on biomass production; class, alternative

and storm event on water retention; and class, alternative, and storm event on

water EC. In this study, it was found that an intensive roof can retain 18% more

precipitation and produce 2.5 times more biomass than an extensive roof.

Design alternatives that employed recycle and run-on techniques produced 26%

more biomass than a conventional ecoroof receiving direct precipitation without

significant reductions in retention. It was demonstrated in this study that the

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runoff from extensive roofs was of higher water quality (lower electrical

conductivity, EC) than from intensive ones.

2.2 Introduction

2.2.1 Ecoroofs

In general, ecoroofs are considered to be oligotrophic ecosystems wherein

ecoroof productivity studies are overlooked when compared to other research

initiatives dealing with plant establishment, temperature and water regulation,

energy balance and wildlife (Peck and Bass 2000; Jones 2002; Dunnett et al.

2005). The few results describing ecoroof productivity are supplemental to

findings in plant establishment or survival studies (Koehler 1990; Koehler 2003).

Yet, research results explaining ecoroof performance, and their associated

environmental benefits, are influenced by growth attributes such as leaf area,

vegetated cover and community composition (Rowe et al. 2003; Wong et al.

2003; Dunnett et al. 2005). This association between environmental benefits and

growth attributes implies that having a better knowledge of ecoroof productivity

would be essential to understanding their performance. This study investigates

the productivity of ecoroofs.

Productivity is a basic attribute of ecosystems (Lieth 1978). It has been

shown that all ecosystems provide essential environmental services to society

through their functions: 1) regulation, 2) habitat 3) production and 4) information

which, in turn, are determined by ecosystem structure and process (Costanza et

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al. 1997; Daily 1997; de Groot et al. 2002). De Groot et al (2002) explain that

each of these four functions is the result of complex natural processes which

have been conveniently grouped. Regulation functions maintain life supporting

systems such as clean air, water and soils, which operate through mechanisms

such as bio-geochemical cycles. Habitat functions provide refuge and allow

plants and animal reproduction to and create the services of genetic diversity and

evolutionary processing. Production functions include photosynthesis and

nutrient uptake by autotrophs to create a variety of carbohydrate structures which

can be used by secondary producers to create greater living biomass.

Information functions provide essential ‘reference’ function to human health in the

cognitive, spiritual, recreational and aesthetic experience realms.

Productivity is influenced by temperature, nutrient and water availability

(Lieth 1973). Subsequently, water has been shown to be involved in plant

ecophysiological processes related to growth such as stomatal conductance,

photosynthesis and carbon and nitrogen partitioning (Eamus 2003). Although

some tropical areas of high precipitation experience lower levels of productivity

due to rapid nutrient loss, in temperate regions productivity is associated with

increased water availability (Clawson et al. 2001; Schuur and Matson 2001).

The study of productivity, which became popular in the middle of the 20th

Century remains effective today a as primary attribute characterizing and

understanding both natural and constructed ecosystems (Kozlovsky 1968;

Kucharik et al. 2001; O’Connell et al. 2003; Takyu et al. 2003). The productivity

theory postulates that productivity influences species richness as a measure of

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diversity. It is also said to influence biotic community function, ecosystem

stability and global health (Naeem et al. 1996; Tilman et al. 1996; Schoen 1997).

The rise of popularity of ecoroofs is due to their potential in reducing

stormwater runoff, ameliorating urban temperatures, creating wildlife habitat and

improving the experience and appearance of the city (Peck and Bass 2000;

Dunnett and Kingsbury 2004). These systems provide benefits from their

ecosystem functions. For example, the systems function to regulate hydrologic

and atmospheric cycles, which has been shown to prevent stormwater runoff in

retention studies (Scholz-Barth 2001; Koehler et al. 2002; Miller 2002; Lipton and

Strecker 2003; Rowe et al. 2003; Dunnett et al. 2005; Hunt and Smith 2005).

Intercept solar radiation by the vegetation which cools the air through

evapotranspiration (Onmura et al. 2001; Liu and Baskaran 2003; Wong et al.

2003). Create habitat for both flora and fauna in which extirpated terrestrial plant

populations and rare invertebrates have been conserved in ecoroofs, while

newer roofs areas are being used for refuge by common insects and birds (Jones

2002; Kadas 2002; Gedge 2003; Brenneisen 2004; Coffman and Davis 2005).

The systems function to provide information through spiritual and aesthetic

experiences for urbanites who are isolated from natural environments

(Osmundson 1999). Production in ecoroofs, on the other hand, has not been

largely studied.

The reasons to investigate productivity in ecoroofs are: 1) it is a basic

attribute of an ecosystem as shown by Lieth (1978) 2) productivity is linked to

other ecosystem functions, such as biodiversity and community stability, and may

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contribute to ecological theory (Naeem et al. 1996), 3) productivity appears to

affect the environmental benefits provided by ecoroofs (Brenneisen 2003; Wong

et al. 2003) and 4) advocates in the public realm are currently proposing

productivity as a way to maximize environmental benefits in ecoroofs

(Mankiewicz and McDonnell 2006). Therefore, in this study I investigate net

primary production of the two major types of ecoroof in two alternative designs to

provide comparison and understanding of these constructed ecosystems.

2.2.2 Productivity in ecoroofs

Ecoroofs are categorized by their substrate depth and their plant

community. There are two classes of ecoroofs, extensive and intensive;

Extensive are those possessing less than 15 cm of substrate depth and

composed largely of plants of the Crassulaceae family. On the other hand,

intensive roofs have more than 30cm of substrate depth and are composed of a

“greater variety” of plants including those with woody stems. Ecoroof substrate

depth correlates positively with water retention and plant diversity, where woody

stemmed shrubs, may only exist in the deeper substrates (Peck and Bass 2000;

Scholz-Barth 2001; Miller 2002; Dunnett and Kingsbury 2004). However, I did

not find in my literature search any studies recording the quantitative values for

productivity across class.

Productivity in ecoroofs has been included in regulatory, habitat and

information studies and it appears to influence results in stormwater retention,

thermal and biodiversity performance (Rowe et al. 2003; Wong et al. 2003;

Brenneisen 2004). One of the most obvious determinants of ecoroof productivity

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is water availability. In ecoroofs stormwater studies Rowe et al. (2003) showed

that vegetative cover significantly impacts retention. In their study of water

retention performances across several substrate depths and mixes, they

demonstrated that greater retention was observed on roofs that possessed

vegetative cover. They also demonstrated that greater substrate depth retained

more precipitation, and a planted and deeper substrate retained the most water.

However, their experiments were limited to a maximum of depth of 10 cm. As a

consequence, they assessed only the extensive class.

Additionally, studies on the microclimatic temperature regulation of

ecoroofs have demonstrated that increased leaf area enhanced ambient air

temperature reductions in field studies, using thermodynamic models (Wong et

al. 2003; Clark 2005; Currie and Bass 2005 ). Wong et al (2003) examined

ambient air temperatures in a vertical section of an ecoroof demonstrating that

from a thermal protection perspective it is desirable to have plants with a high

leaf area index. Their results indicated that this may require an intensive class

ecoroof. Clark (2005) demonstrated that removal of atmospheric NOx (Nitrogen

Oxide) was dependent on leaf area as well. His study found that larger leaf area

in the C3 plant Nicotiana tabacum, contributed to an improved performance in

annual NOx removal over the CAM plant Kalanbloss feldiana. However, Clark

failed to explore the depth of substrate required to growth these two plants in

ecoroofs. N. tabacum, may require an intensive ecoroof depth level of substrate

for plant growth. Currie and Bass (2005) in an urban scale modeling study

proposed grasses to be used on ecoroofs to decrease urban air pollution. The

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use of grasses would also necessitate constructing an intensive ecoroof as it has

been shown that grasses have poor establishment in extensive roofs. (Rowe et

al. 2005). These studies illustrate that productivity appears to be associated with

substrate depth and that distinction amongst substrate depths has not been

considered in experimentation and modeling.

At this time, only three studies list productivity (growth) rates as part of

larger research objectives involving ecoroofs and plants (Koehler 1990; Koehler

2003; Rowe et al. pending). Koehler (2003) states ecoroof plant development is

influenced by 1) the water holding capacity of the system 2) the planting method

3) the building architecture and 4) the maintenance of the vegetation stand. He

compiled information and drew conclusions from eight separate study sites that

have recorded data over eighteen years. He states that the phytomass (whole

plant dry weight) presented in these studies ranged between 4.2 g·m-2 and 47.2

g·m-2. Unfortunately, he presents only one value for the leaf area index (0.64)

and the shoot to root ratio (0.9) without explaining how they are related.

Although plant survivability is influenced by various environmental

variables, water remains an important factor contributing to ecoroof plant growth

(Mentens et al. 2003). It has been determined that substrate water retention is a

function of its volume, and that such retained water is used by plants (Miller

2002). These two works illustrate the relationships of productivity to substrate

depth.

Advocates in the public realm are proposing new ways to maximize the

environmental benefits of ecoroofs by varying substrate depth and capturing or

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recycling water and nutrients (Brenneisen 2003; Kula 2005). Brenneisen (2003)

found that diversity of insects and birds, positively correlated with plant diversity,

which was created by hummock areas in extensive roofs. In a five year study

evaluating 24 ecoroofs, it was shown that primary and secondary biodiversity

was greater on roofs with topographic diversity. Hummocks, of substrate ranging

from 15 cm to 30 cm existed on many extensive roofs, making them “semi-

intensive”. Resulting from this study has been the establishment of municipal

codes in Basel and Zurich requiring ecoroofs designed to increase biodiversity

through the use of hummocks (Brenneisen 2005).

The use of grey water recycling or collecting water stormwater from

nearby roofs is likely to impact the productivity within an ecoroof. Several

alternative ecoroof designs using recycled water are being constructed to

maximize stormwater retention and maximize evapotranspiration. Under the

concept of zero-discharge, a system aims to capture, rainwater in cistern storage

for later recycle or collecting roofs which drain to ecoroofs in order to further

reduce, or eliminate runoff by maximizing evapotranspiration rates (Shirley-Smith

2003; Kula 2005; Compton and Whitlow 2006; Mankiewicz and McDonnell 2006).

Mankiewicz and McDonnell (2006) propose using a building’s grey water, which

is domestic waste water from washing dishes and other low contaminant

sources, to irrigate a plant palette consisting of species possessing high levels of

stomata conductance in order to increase evapotranspiration rates in the entire

ecoroof. Compton and Whitlow (2006) explored both obligate wetland species

and facultative upland pioneering colonizers in ecoroof in order to optimize

69

evapotranspiration rates. Their preliminary results show zero discharge. These

zero-discharge designs are considered more valuable to sustainable design

organizations such as the United States Green Building’s Council’s Leadership in

Energy and Environmental Design (LEED) (Kula 2005) because they prevent all

stormwater discharge.

The intent of my study was to compare productivity and stormwater runoff

for two soil depths and two design alternatives to improve the understanding of

ecoroof productivity and retention. My objectives were first, to determine if

productivity could be increased through alternative designs, such as recycle or

run-on, as well as record the influence of substrate depth on biomass

development. Second, I expected to determine if water retention would be

greater in the alternative ecoroofs when compared to a conventional ecoroof

receiving only direct precipitation, as well as, confirm that deeper substrates

improve retention. Lastly, I expected to ascertain any differences in electrical

conductivity (EC) in the leachate from the ecoroofs.

2.3 Material and methods

2.3.1 Constructed Plots

Twenty four experimental vegetated roof system plots were built

approximately one meter above the ground on a crushed stone nursery pad at

The Ohio State University agricultural farm, Columbus, OH USA (40o N latitude)

in the spring of 2004 (Fig. 2.1 and 2.2). All 24 plots were 1m2. In order to

create two classes, depth in 12 plots was 10 cm (extensive) and in the other 12,

70

it was 30 cm (intensive) The plots were constructed with treated pine wood with

sidewalls to create the appropriate parapet roof depth. The entire parapet was

covered with bituminous waterproof roofing membrane from the Garland

Company, Cleveland Ohio and fitted with a single pvc drain, a drainage and filter

layer and a root barrier layer from Garland’s Greenshield line of products. Under

each plot, there was either a 18.9 L or a 60 L bucket for the collection of storm

water runoff. Garland’s Greenshield Oasis 321 was the substrate added to

specified depths of 10 cm or 30 cm. The substrate properties provided by the

company were Void ratio ≥ 15%; moistures content≥15%; maximum water

capacity ≥ 45%; saturated hydraulic conductivity ≥ 1.91 cm•hr and ≤ 20.2 cm•hr;

pH 5.5 to 6.5 soluble salts <= ≤ 0.30 mmhos•cm. The substrate is considered to

be low fertility and no fertilizers were applied in the experiment. The following

plant species and quantities were planted in each plot: 9 Schizachyrium

scoparium (Little blue stem), 9 Rudbeckia hirta (Black eyed susan), and 5 Rhus

aromatica ‘Gro Low’ (Low grow sumac). The plants were grouped by species

within each plot to reduce errors in harvesting. The experiment was initiated in

June 2004.

The apron alternative was constructed with an additional 1 m2 apron

designed to direct stormwater into the ecoroof, thus doubling the volume of

precipitation with each rain event (Fig 2.2). The alternative r (recycle) received

supplemental grey water irrigation to field capacity every two weeks on non-

storm event days. All plots were equipped to receive both natural and simulated

storm events and measure discharge quantity and quality in collection

71

containers. Three simulated storms were performed in the second growing

season delivering 2.54 cm (1”) in ten minutes from an irrigation system. The

irrigation system consisted of 2 Microjet spray heads per plot, (Model SXB-360

Rainbird). Each apron alternative received two additional heads for the apron.

The storm system was calibrated prior to every simulated event and recalibrated

once during the event. Substrate moisture tension was recorded with a

tensiometer (Model MLT, Irrometer Company, Inc, Riverside, CA), inserted to 5.1

cm (extensive) and 20.3 cm (intensive) for 60 days during the growing season of

2005. Water quality was tested using digital by with for electrical conductivity

(EC) (Twin condmeter B-173, Spectrum Technologies, Plainfield IL) and pH

(Twin pHmeter B-213, Spectrum Technologies, Plainfield IL).

Figure 2.1. General view of the plots located in the Waterman Farm at the OSU

campus, Columbus, OH

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Figure 2.2. Plot Layout. Class: e (extensive) or i (intensive). Alternative: a

(apron), d (direct), r (recycle) and c (control). Aprons are shown as attached

squares with an X drawn on them.

73

2.3.2 Experimental Design

The experiment was designed for paired analysis, first by class and then

by alternative. The two classes, extensive and intensive, and all treatments were

randomly assigned (Fig. 3.2). The treatments were:

1. control, (unplanted roof)

2. direct precipitation, (conventional design)

3. apron, (run-on)

4. recycle, (leachate recycled)

2.3.3 Data collection

Data were collected over two growing seasons from June 2004 to Sept

2005. Storm water data were collected from nine natural storm events and three

simulated storm events.

Biomass was measured after whole plant harvesting. First initial biomass

measurements were taken at planting and total crop harvesting was done after

the second season. The samples were harvested (including roots), root washed,

and dried at 55oC in a drying oven for 72 hours and then weighed.

A total of three natural rain events were recorded in 2004 and nine rain

events including all natural and simulated events were recorded in summer 2005.

Rainfall within a 24hr period constituted a natural event. Rainfall was recorded

on site and water volume entering each plot was measured. Runoff was collected

directly under the plot in individual containers where volume was determined by

dipstick and calculations. Percent of retention for each plot was determined.

Water quality was also tested with calibrated digital instruments form each

74

collected sample. During the second growing season, substrate moisture tension

was measured with a tensiometer and recorded.

2.3.4 Data analysis

Data were analyzed using ANOVA and the General Linear Model to

assess the main effects and possible interactions among the independent

variables, class and alternative, on the dependent variable biomass, retention,

EC and pH with covariates storm quantity and plant type. Tukey's multiple

comparison method was used to determine significant differences among the

levels of each independent variable. To examine biomass per plot, the Friedman

two way nonparametric ANOVA was used. Biomass data sets examined for the

combined years, as well as, separately. Pearson's correlation was used to

assess association between biomass and storm water as well as EC, pH and

biomass interactions. (For tables see Appendix I.)

2.4 Results

2.4.1 Biomass

Class, alternative, and plant species all had a significant effect on total

biomass (Appendix B). A multiple comparison demonstrates differences within

class and alternative and amongst alternative by class. The multiple comparison

shows that intensive class produced 2.7 times more biomass than the extensive

class (Fig. 2.3). The apron and recycle alternatives produced significantly greater

biomass than the direct (Fig. 3.4). Assessment by alternative and class shows

that amongst each alternative, there are significant differences in class (Fig. 3.5).

75

Black eyed Susan, Rudbeckia hirta, was lost in all roofs after the first year. S.

scoparium and R. aromatica ‘Gro Low’ had significantly different biomass (P <

0.001, 95% CI). S. scoparium developed 2.8 times more biomass than R.

aromatica (Fig.2.6)

Figure 2.3. Mean productivity measured as whole plant biomass by class (±SE)

(P-value < 0.001, 95% CI). Bars with same letter are not significantly different.

76

Figure 2.4. Mean productivity measured as whole plant biomass by alternative (±

SE.) (All P-values are < 0.05, 95% CI). Bars with same letter are not significantly

different.

77

Figure 2.5. Mean productivity measured as whole plant biomass by alternative

and class (± SE.) (All P-values are < 0.05, 95% CI). Bars with same letter are not

significantly different.

78

Figure 2.6. Mean productivity measured as whole plant biomass per species (±

SE.) (P < 0.001, 95% CI). Bars with same letter are not significantly different.

2.4.2 Retention

Class, alternative and storm volume had a significant effect on retention

(Figs. 2.7 – 2.9 and Appendix B). A multiple comparison demonstrated a

difference within class and alternatives, and among alternatives by class (Fig.

2.9).

The multiple comparison results indicated that the intensive class had

significantly greater storm water retention than the extensive class (Fig. 2.7). The

intensive class retained 18.1% more precipitation than the extensive. The direct,

79

recycle and apron alternatives have significant greater retention than the control.

However, there was no significant difference between direct, recycle and apron

alternatives (Fig. 2.8). Assessment by alternative and class shows that amongst

each alternative, there are significant differences in class (Fig. 2.9). There was

no significant difference between the natural storm and the simulated storm (Fig.

2.10).

Figure 2.7. Mean water retention by class (± SE). (P < 0.001, 95% CI) Bars with

same letter are not significantly different.

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Figure 2.8. Mean water retention by alternative irrespective of class (± SE). (All P

values are < .05, 95% C.I.) Bars with same letter are not significantly different.

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Figure 2.9. Mean water retention of alternative by class (± SE). (All P-values are

< .05, 95% C.I.). Bars with same letter are not significantly different.

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Figure 2.10. Mean water retention of storm events (± SE). (P < 0.05, 95% CI)

Bars with same letter are not significantly different.

2.4.3 Water Quality

Class, alternative, and date of event variables have a significant effect on

the electrical conductivity (EC) in the leachate (Fig. 2.11-2.13 and Appendix II

Tables 5 and 6). The intensive class had significantly higher EC values than the

extensive class (Fig. 3.11). The recycle and control alternatives recorded the

highest EC by class. Although they were not significantly different from one

another, both were significantly different than the apron and direct. (Fig. 2.12).

When separated by alternative and class, there they exhibited the same pattern

(Fig. 2.13). There was no difference in pH between classes (Fig. 2.14).

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However, the recycle and control alternatives had significant higher pH than the

apron alternative. The recycle alternative had significant higher pH than the direct

alternative. (Fig. 2.14)

Figure 2.11. Mean Electrical Conductivity (EC) in the runoff water by class (mean

± SE). (P < 0.001, 95% CI). Bars with same letter are not significantly different.

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Figure 2.12. Mean Electrical Conductivity (EC) in the runoff by alternative

irrespective of class (± SE). (All P values are < .05, 95% C.I.) Bars with same

letter are not significantly different.

85

Figure 2.13. Mean Electrical Conductivity (EC) in the runoff by alternative and

class (± SE). (All P values are < .05, 95% C.I.) Bars with same letter are not

significantly different.

86

Figure 2.14. Mean pH in the runoff by alternative irrespective of class (± SE). (All

P values are < .05, 95% C.I.) Bars with same letter are not significantly different.

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Figure 2.15. Mean pH in the runoff by alternative irrespective of class (± SE). (All

P values are < .05, 95% C.I.) Bars with same letter are not significantly different.

2.4.4 Interactions

A regression analysis showed that biomass predicted by water retention

was good where 82.6% of the variation in productivity can be explained by

changes in retention (R2= 0.8262 y = 6.3496x - 70.801) (Fig. 3.16). Separating by

alternative improved predictability (R2=0. 976direct, R2=0.971recycle, R2=0.938

runoff). The direct and apron alternatives had more consistent relationship

between biomass and retention than the recycle alternative (Fig. 2.17).

The substrate moisture tension comparison demonstrates that the

substrates of the extensive class dried faster than those of the intensive class

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(Fig. 2.18). Also, mean moisture tension in the substrate of the direct, apron and

control alternatives rose more quickly than the recycle alternative for both

classes (Fig. 3.19-3.20).

Figure 2.16. Linear regression of biomass predicted by retention shown with

observed values as symbols ( y = 6.3496x - 70.801 R2= 0.8262).

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Figure 2.17. Linear regression of biomass predicted by retention by alternative

regardless of class shown with observed values as symbols. (Direct; y = 5.1658x

- 60.425 R2 = 0.976 Recycle, y = 6.4007x - 61.433, R2= 0.971. Apron y =

9.0247x - 138.61, R2= 0.9382).

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Figure 2.18. Mean moisture tension in the substrate by class observed values as

symbols an predicted values as an exponential curve; extensive (y = 4.3261e

0.2179x) and intensive (y = 3.2342e 0.2283x).

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Figure 2.19. Mean moisture tension in the substrate for the extensive class

alternatives shown observed values as symbols an predicted values as an

exponential curve; direct y = 4.3261e 0.2179x), apron (y = 4.298e 0.2394x), control (y

= 3.4185e 0.2795x) and recycle (y = 3.0663e 0.2025x ).

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Figure 2.20. Mean water tension in the substrate for the intensive class

alternatives shown with observed values as symbols an predicted values as an

exponential curve; direct (y = 3.2342e 0.2283x), apron (y = 3.5781e 0.2376x), control

(y = 2.6034e 0.201x) and recycle (y = 2.5819e 0.1769x ).

2.5 Discussion

The intensive class producing 2.7 times more biomass than the extensive

class (Fig. 2.3) can be explained largely by greater water retention capacity in the

substrate volume that is provided by the increased depth (Fig 2.7). Rowe (2003)

observed that vegetative cover of identical plant communities increased with

increasing substrate depths in extensive systems. Miller (2002) has

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demonstrated that substrate depth positively correlates to water holding capacity.

Figure 2.7 and 2.18 demonstrate that the intensive class retains more water

(18% more of the precipitation) and dries more slowly than the extensive making

more water available to plants over a longer period of time.

Plant selection impacted ecoroof productivity. S.Scoparium produced

more biomass than R. aromatica. By using non-typical extensive ecoroof plants,

this study showed higher levels of productivity; 72.8 g·m-2 compared with 48.4

g·m-2 from the Koehler (1999) study. The previous study used succulent plant

selections, rather than grass or woody vegetation which possibly reduced

productivity. Rudbeckia hirta was used as a native perennial and was guaranteed

by the grower as such, however, it behaved as an annual, perhaps due to

environmental stresses such as lack of water or low temperatures. Subsequently,

a study by Monterrusso et al (2005) presents the result of low over wintering

mortality and survivability in R. hirta. The cause for loss can be attributed to a

limited root growth environment insufficient in water, nutrients and thermal

protection.

Using different alternatives demonstrated that water distribution impacted

productivity. The greater biomass of the apron and recycle alternatives may be

attributed to greater volumes of water entering the system during the growing

season. In the recycle alternative water was added every two weeks to field

capacity. The apron received twice the regular precipitation during storm events

that often went beyond holding capacity. One first time finding was that the

recycle substrate dried more slowly than all other roofs, while the apron substrate

94

dried more quickly than all others. This can partially be explained by the

distribution of water. By distributing leachate water during non-storm event days

to the recycle alternative the substrate remained moist for longer periods. During

those periods more water was availability to the plants. The influence of

availability of water on plant growth is addressed by Koehler (1990). The quicker

drying substrate in the recycle is difficult to explain and requires further

investigation.

The reason the extensive class had less water retention than the intensive

one is largely due to a greater water holding capacity of the deeper substrate.

Mentens et al. (2003) explains that roof properties including substrate depth are

a primary factor influencing water holding capacity. However, it likely could be by

higher plant growth, but also it is influenced by the volume of precipitation. These

results support previous findings by Rowe et al (2003) where volume of

precipitation and roof depth are considered to be the factors influencing retention.

However, it could also be due the evapotranspiration of the grasses in the

intensive systems. Evapotranspiration rates have been shown to be higher in

planted extensive ecoroofs than unplanted (Beattie et al. 2002). Because

biomass in the intensive treatment was 2.5 times that of the extensive one it can

be speculated that more water was being used by the plants. Compton and

Waller (2006) recorded higher evapotranspiration rates in fast growing C3

grasses supporting the idea that roofs with high growth rates use more water.

It is generally understood that plants will utilize the nutrients in the ecoroof

substrate and those arriving from atmospheric deposition, thus preventing

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nutrient export (Peck et al. 1999). However, Hunt et al. (2006) showed that

leaching is also a function of substrate composition. Differences in leachate

quality indicators in this study such as EC and pH, can be partially explained by

considering water distribution and the presence of plants. The recycle alternative

recorded higher levels of EC than both the direct and the apron. It also recorded

the highest (neutral) pH. These occurrences could be caused by the

redistribution of leachate as irrigation water in the recycle alternative. In this

scenario leachates do not exit but instead accumulate in the system. The control,

which was unplanted, shows the effect of plants on EC. Plant presence may

decrease EC levels in leachate. Roots contribute to the organic matter of a soil.

The organic matter has high cation exchange capacity and retains some of the

cations that may otherwise be leached. This could be enhanced by the use of

light weight expanded aggregate which possess nutrient and bacteria absorption

capacities (Eikebrokk 2001 ).

When compared to EC in previous studies of nearby receiving streams,

leachate from all vegetated roofs system showed lower EC. In a study by Spieles

and Mitsch (2000) stream EC ranges were recorded between 0.348 - 0.701

mS•cm-2 compared to the range of 0.152-0.168 mS•cm-2 recorded in the

ecoroofs.

One question asked by developers and conservationists is whether

ecoroofs can be built to recreate local habitat that is being destroyed by the

proposed building. Although it is possible to create some form of habitat for

local species using ecoroof systems, the re-creation of the local habitat on a

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rooftop appears unrealistic. The mean productivity of ecoroof systems in this

study when compared to other studies of terrestrial ecosystems was much lower.

The extensive ecoroofs (72 g·m-2·yr ) are lower than a desert scrubland (90 g·m-

2·yr ) and intensive ecoroofs (193 g·m-2·yr ) are slightly higher than an alpine

tundra (140 g·m-2·yr). They are both lower in mean productivity than that of

natural grasslands (600 g·m-2·yr ) and a woodland shrublands (700 g·m-2·yr ), but

certainly higher than extreme deserts (3 g·m-2·yr ) (Whittaker and Likens 1975).

Even the most productive systems, the alternative designs (210 g·m-2·yr), were

much lower than the local forest biome (700 g·m-2·yr) in which the experiment

occurred. This confirms the oligotrophic label placed upon the systems by

Koelher (2003). It also reinforces the position that ecoroofs are “new”

ecosystems incapable of recovering local terrestrial ecosystem loss when

constructed with in a temperate biome (Scholz-Barth 2001).

These findings show that the alternative designs apron and recycle do not

significantly compromise stormwater retention. This is important information to

ecoroofs built with recycling and collection systems. However, important to

retention is the distribution of the water relative to the water holding capacity and

frequency of storms.

2.6 Conclusions

The study shows that ecoroof productivity can be predicted largely by

water retention. Productivity increased through alternative designs capturing

more water, such as recycle or run-on. The increasing of substrate depth

improved biomass development. Also, water retention was greater in the

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alternative ecoroofs when compared to a conventional ecoroof receiving only

direct precipitation. Equally, retention improved in deeper substrates. Lastly,

there were differences in electrical conductivity (EC) in the leachate from the

ecoroofs.

It was shown that an intensive green roof produces greater amounts of

biomass and retains more precipitation, while having higher levels of dissolved

salts in discharge waters than extensive roofs. The retaining of additional storm

water in the roof system during the growing season is related to greater plant

biomass, however, not necessarily related to dissolved salts and pH. Designing

of green roofs to use recycled storm water or catch additional storm water on

aprons creates greater levels of plant growth and may not significantly reduce

storm water retention performance in those same roofs. Additionally, recycling

ecoroof runoff as grey water irrigation can elevate the dissolved salts and the pH

of the discharge.

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Brenneisen, S. (2003). Biodiversity of European greenroofs. In conference

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Brenneisen, S. (2004). From Biodiversity to Agricultural Productivity. In

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Brenneisen, S. (2005). Green roofs recapturing urban spaces for wildlife- A

challenge for urban planning and environmental education. In conference proceedings of Greening Rooftops for Sustainable Communities Washington D.C. Green Roofs for Healthy Cities

Clark, C. (2005). Optimization of green roofs for air pollution mitigation. . In

conference proceedings of Greening Rooftops for Sustainable Communities Washington D.C.

Clawson, R. G., B. G. Lockaby and B. Rummer (2001). "Changes in production

and nutrient cycling across a wetness gradient within a floodplain forest." Ecosystems 4.

Coffman, R. and G. Davis (2005). Insect and Avian Fauna Presence on the Ford

River Rouge Green Roof. In the conference proceedings of Greening Rooftops for Sustainable Conference, Washington DC, Green Roofs for Healthy Cities.

Compton, J. S. and T. H. Whitlow (2006). A zero discharge green roof system

and species selection to optimize evapotranspiration and water retention. In conference proceedings of Greening Rooftops for Sustainable Communities Boston, MA.

Costanza, R., R. d'Arge, R. de Groot, S, S. Farber, M. Grasso, B. Hannon, K.

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Currie, B. A. and B. Bass (2005 ). Estimates of air pollution mitigation with green plants and green roofs using the UFORE model In conference proceedings of Greening Rooftops for Sustainable Communities Washington D.C.

Daily, G. C., Ed. (1997). Nature's Services: Societal Dependence on Natural

Ecosystems. Washington D.C., Island Press. 394pgs. de Groot, R. S., M. A. Wilson and R. M. J. Boumans (2002). "A typology for the

classification, description and valuation of ecosystem functions, goods and services." Ecological Economics 41: 393 - 408.

Dunnett, N. and N. Kingsbury (2004). Planting Green Roofs and Living Walls.

Portland, OR, Timber Press. Dunnett, N., A. Nagase, R. Booth and P. Grime (2005). Vegetation composition

and structure significantly influence green roof performance. In conference proceedings of Greening Rooftops for Sustainable Communities, Washington, D.C.

Eamus, D. (2003). "How does ecosystem water balance affect net primary

productivity of woody ecosystems?" Functional Plant Biology 30: 187-205. Gedge, D. (2003). '...From rubble to Redstarts...' In conference proceedings

Greening Rooftops for Sustainable Communities Chicago, Green Roofs for Healthy Cities

Hunt, W. and J. Smith (2005). Hydrologic and water quality performance from

green roofs in North Carolina. In conference proceedings of Greening Rooftops for Sustainable Communities, Washington D.C. Green Roofs for Healthy Cities

Jones, R. A. (2002). Tecticolous Invertebrates. A preliminary investigation of the

invertebrate fauna on green roofs in urban London. London, English Nature: 36.

Kadas, G. (2002). Study of invertebrates on green roofs - How roof design can

maximise biodiversity in an urban environment. Dept. of Geography. London, University College. MSc Conservation: 76.

Koehler, M. (1990). The living conditions of plants on the roofs of buildings.

Urban Ecology: Plants and the plant communities in urban environments. H. F. H. Lieth. Stroudsburg, PN, Dowden, Hutchinson & Ross.

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Koehler, M. (2003). Plant Survival Research and Biodiversity: Lessons From Europe. In conference proceedings of Greening Rooftops for Sustainable Communities, Chicago, IL. Green Roofs for Healthy Cities

Koehler, M., M. Schmidt, F. W. Grimme, M. Laar, V. L. d. A. Paiva and S.

Tavares (2002). "Green roof in the hot-humid tropics- far beyond aesthetics." Environmental Management and Health 13(4): 382-391.

Kozlovsky, D. (1968). "A critical evaluation of the trophic level concept:

Ecological efficiencies." Ecology 49: 48-60. Kucharik, C. J., K. R. Brye, J. M. Norman, J. A. Foley, S. T. Gower and L. G.

Bundy (2001). "Measurements and Modeling of Carbon and Nitrogen Cycling in Agroecosystems of Southern Wisconsin: Potential for SOC Sequestration during the Next 50 Years." Ecosystems 4: 237-258.

Kula, R. (2005). Green roofs and the LEED green building rating system. In

conference proceedings of Greening Rooftops for Sustainable Communities, Washington D.C.

Lieth, H. (1973). "Primary production: terrestrial ecosystems." Human Ecology 1:

303-332. Lieth, H. F., Ed. (1978). Patterns of Primary Production in the Biosphere.

Benchmark Papers in Ecology. Stroudsburg, PN, Dowden, Hutchinson & Ross.

Lipton, T. and E. Strecker (2003). EcoRoofs (Greenroofs)- A more Sustainable

Infrastructure. National Conference for Stormwater Managers, Portland, OR. Green Roofs for Healthy Cities

Liu, K. and B. Baskaran (2003). Thermal performance of green roofs through

field evaluation. In conference proceedings of Greening Rooftops for Sustainable Communities Chicago. IL. Green Roofs for Healthy Cities

Mankiewicz, P. S. and T. McDonnell (2006). Sustainable green roof design:

Optimizing water budgets through wastes-into-resources technologies in the Bronx. In conference proceedings of Greening Rooftops for Sustainable Communities Boston, MA. Green Roofs for Healthy Cities

Mentens, J., D. Raes and M. Hermy (2003). Effect of orientation on the water

balance of greenroofs. In conference proceedings of Greening Rooftops for Sustainable Communities Chicago. IL. Green Roofs for Healthy Cities

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http://www.roofscapes.com/benefits.html.

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Naeem, S., K. Hakansson, J. H. Lawton, M. J. Crawley and L. J. Thompson

(1996). "Biodiversity and plant productivity in a model assemblage of plant species." Oikos 76: 259-64.

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Onmura, S., M. Matsumoto and S. Hokoi (2001). "Study on evaporative cooling

effect of roof lawn gardens." Energy and Buildings 33: 653-666. Osmundson, T. (1999). Roof gardens : history, design, and construction. New

York, W.W. Norton. Peck, S. and B. Bass (2000). Green Roof Infrastructure Workshop: Establishing

Common Protocals for Building and Aggregate Level Green Roof Benefits Research. Toronto, University of Toronto: 43.

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expanded Slate and Fertility Requirements in Green Roof Substrates." HortTech 16(3): 321-332.

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CHAPTER 3

ECOROOFS AND BIODIVERSITY: ASSESSING ANIMAL DIVERSITY ON TWO

TYPES OF VEGETATED ROOFS

3.1 Abstract

This study provides a description of animal diversity on two dissimilar,

vegetated roofs, and it promotes a general methodological approach for such

studies. I used a rapid assessment method to quantify the diversity of insects,

spiders and birds on these ecoroofs. I describe diversity using presence-

absence and relative abundance data. Birds were assessed at the species level,

and insects and spiders were assessed at higher taxonomic levels. The Rènyi

family of diversity indices, which encompass conventional metrics, was used to

compare animal diversity between the two ecoroofs. My data revealed relatively

low similarity between the ecoroofs, with some key differences. Overall, the

intensive ecoroof supported slightly higher diversity. Spider diversity was most

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similar between the ecoroofs, followed by insect diversity, while the species

assemblages of birds were entirely distinct. I promote the methodological

approach used here, speculate on why diversity differed between the ecoroofs,

and discuss conservation implications of these constructed habitats.

3.2 Introduction

In keeping with the goal of increasing local biological diversity, one urban

development practice, known as roof greening, provides habitat for wild species

within cities (Peck et al. 1999; Dunnett and Kingsbury 2004). This practice is not

a form of restoration ecology, but rather a form of reconciliation ecology, where

new habitat is created for nonhuman species (Rosenzweig 2003). While all

vegetated roofs inevitably provide some form of habitat, presumably the

properties of the roof, the type of vegetation used, and the overall design will

combine to impact animal diversity (Jones 2002; Brenneisen 2003; Brenneisen

2006). Studies aimed at evaluating these potentially complex impacts are in their

infancy. Here, I attempt to redress two weaknesses of prior studies. First,

although ecoroofs vary in character and size, so far biodiversity assessments

have been limited to a single major type of ecoroof within each study. Thus,

whether the observed patterns of diversity are generalizable to other kinds of

ecoroofs remains doubtful. Second, although ecoroofs are supposedly designed

to enhance biodiversity across taxa, most assessments to date have examined

just a single taxon (e.g. insects). Therefore, a method is needed for efficient

assessment of diversity across taxa and across roof types and sizes. Ideally,

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any such method would provide reliable descriptions of ecoroof biodiversity,

which could be compared to make inferences about which types of ecoroof

provide the best habitat, while recognizing that even the best such constructed

habitat could be sink rather than habitat for some taxa and so could have

detrimental impacts.

A vegetated roof, or ecoroof, is simply vegetation growing on a building’s

rooftop. Superficially, these roofs provide a suite of environmental benefits:

stormwater retention (Scholz-Barth 2001; Miller 2003; Rowe et al. 2003), energy-

use reduction (Onmura et al. 2001; Wong et al. 2003; Gaffin et al. 2006), food

production (Tinkel 1977), and habitat creation (Jones 2002; Brenneisen 2005).

Attempts to maximize these various benefits have resulted in variation among

vegetated roof systems. Two accepted types of vegetated roof systems are

based largely on structure rather than function. The first is an extensive system

consisting of <10 cm of substrate and allowing for only a few plants species,

which is designed to reduce energy demands and stormwater runoff. The other

is an intensive system consisting of soil medium >30 cm and allowing for

numerous plant species, which is often designed for aesthetics. (Peck et al.

1999; Dunnett and Kingsbury 2004). Ecoroofs could be categorized based on

various other features, but I use this simple distinction between extensive and

intensive systems throughout.

Studies quantifying biodiversity on vegetated roofs have so far relied on a

single diversity index (e.g., species richness, Shannon, Simpson). Such studies

depend on high investments of labor and often yield inaccurate point estimates

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that are of limited use for comparisons across types of ecoroofs (Wilhm 1970;

Lande 1996; Gotelli and Colwell 2001). A seemingly preferable alternative to this

approach might use rapid assessment methods combined with a general

statistical method for quantifying diversity. In particular, I advocate using the

Rènyi equation to calculate the entire family of diversity indices. The resulting

curve encompasses special cases, which include species richness, Shannon

diversity, Simpson diversity, and so on. By generating the entire curve, a fuller

comparison of diversity among ecoroof types becomes possible. Despite the

obvious advantages, Rènyi diversities have not been used to date in studies of

ecoroof biodiversity.

Here, I use this approach to compare animal diversity on an extensive

ecoroof versus an intensive ecoroof. These ecoroofs were constructed under

alternative priorities, including energy, stormwater and aesthetics, so they may

thus differ in the kinds of habitat they provide and biodiversity they support. Our

study was performed in the summer of 2004 at two locations in the Upper

Midwest Great Lakes region of the United States (Fig. 3.1). The objective was to

quantify and compare animal diversity between the two ecoroofs based on

presence data of various taxa. Rather than simply comparing species richness

or some other single conventional metric, we use the Rènyi method to offer a

fuller description of animal diversity on these ecoroofs.

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Figure 3.1. Map showing the two study sites, e and i.

3.3 Vegetated Roof Systems and Animal Diversity Assessment

These built systems (of constructed materials) have the potential to create

new habitat for wild species, while also providing additional ecosystem services.

Creating habitat so that it may blend with, or even depend upon, human-

dominated ecosystems is a form of reconciliation ecology. Rosenzweig (2003)

advocated ecoroofs in core urban areas as a way to provide new habitat for

species. Almost simultaneously, workers began to document the value of

vegetated roofs as habitat.

Studies on insects and spiders have been carried out in England and

Switzerland, mostly on extensive roofs, including some with hummocks or

mounds of substrate. Some surveys have focused on beetles and spiders

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(Kadas 2002; Brenneisen 2003), while one study described the community of

large invertebrates (Jones 2002). Some surveys have simply quantified species

richness (Jones 2002), while others have quantified Shannon diversity (Kadas

2002; Brenneisen 2003). All studies have documented the presence of rare

insects (www.iucn.org), regardless of ecoroof structure. The spider and beetle

studies showed significant differences in diversity across ecoroofs, while the

large-invertebrate study did not. The spider and beetle diversity differences were

found to be associated with abiotic factors of the ecoroof structure.

Ecoroof systems with a variety of substrate depths and vegetation types

tend to have higher spider, beetle and bird diversity (Brenneisen 2003).

Brenneisen (2003) showed that “contouring” vegetated roof systems with

hummocks apparently led to increased diversity. Prompted by these findings,

design criteria have emerged. These criteria stipulate the use of local soils,

native plants, and a variety of substrate properties and microtopographies.

Constructing systems using these criteria has been shown to increase species

richness during the establishment period (Brenneisen 2006).

Although vegetated roofs as habitat operate under the “Field of Dreams”

premise, where “if you build it, then they (wild species) will come,” a wide range

of priorities exist within this practice. At the highest level of priority, a very small

number of systems are designed to maximize biodiversity. At the lowest, most

common level of priority, potential impacts on biodiversity are only casually

considered. Any resultant habitat is seen as a perk to wildlife and society. In

response to this neglectful approach, incentives and regulations for designing

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ecoroofs with biodiversity goals have arisen in both Switzerland and England

(Gedge 2003; Brenneisen 2005). In Switzerland, new vegetated roof systems

must pass a review of their biodiversity design (Brenneisen 2005). Many roofing

systems use local cobble-based soils as substrate, local vegetation, and

connections to terrestrial habitat to enhance colonization. Likewise, in London, a

metropolis-wide biodiversity initiative advocates the use of vegetated roofs to

enhance biodiversity. Studies in both Switzerland and London have shown the

diversity of spiders and birds on ecoroofs to be comparable with that in

“brownfields” (i.e., gaps in the urban setting that await redevelopment)

(Brenneisen 2003; Gedge and Kadas 2004; Kadas 2006). Therefore all

terrestrial habitats, even urban remnants, could serve as sources for immigrating

ecoroof species.

These findings notwithstanding, studies on the value of ecoroofs as

habitat are barely underway. The current paucity of information on the topic may

be due to several factors. I contend that one contributing factor has been the

reliance on species-level assessment, which demands intensive sampling and

expert identification by trained systematists (Brenneisen 2003; Kadas (2006).

These exhaustive assessments may often be impractical for studies aimed as

evaluating ecoroof habitat. An obvious alternative is to use rapid assessment

methods. These methods could greatly facilitate research, allowing us to assess

the ecological value of vast numbers of roofs designed with the intent of

maximizing biodiversity.

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Because most ecoroofs are designed to enhance biodiversity in

unspecified ways, rather than to provide habitat for target species, rapid

assessment methods could conceivably provide adequate descriptions of

biodiversity. These methods are meant to be efficient. They aim to identify

organisms (usually invertebrates) at higher-than-species taxonomic levels and

thereby avoid wasting time, labor, and money in species-level assessment (Pik et

al. 1999). Rapid assessment is sufficient when identifying organisms to the level

of morphotaxonomic resolution satisfies the research objectives (Ellis 1985;

Ferraro and Cole 1990). These methods have been used in terrestrial (non-

ecoroof) studies of insects (Oliver and Beattie 1996; Pik et al. 1999; Kerr et al.

2000), spiders (Kapoor 2006), and birds (Poulsen and Krabbe 1998).

Despite the efficiency advantage of rapid assessment, this approach has

not been used in any prior study of ecoroof biodiversity. This study therefore fills

a gap in knowledge by quantifying animal diversity on two dissimilar vegetated

roof systems by assessing insects and spiders at higher taxon levels and birds at

the species level.

Studies so far have relied on single diversity indices, such as species

richness or Shannon’s Index, which used alone can often be inaccurate (Wilhm

1970; Peet 1974; Gotelli and Colwell 2001). One alternative to the dependence

on single indices is the Rènyi family of diversity indices (Hill 1973; Walker et al.

2003; Kindt et al. 2006). The Rènyi extends the Shannon Index by calculating the

frequency of each component species and a scale a parameter as:

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Equation 3.1:

The values (Hα) are calculated from the frequencies of each component species

(proportional abundance pi = abundance of species i divided by the total

abundance summed across all species) and a scale parameter (α) ranging from

zero to infinity (Legendre and Legendre 1998 ; Kindt et al. 2006). The following

integer values of α, 0, 1, 2, and 3, correspond to species richness, and the

Shannon, Simpson, and Berger-Parker diversity indices, respectively (Kindt et al.

2006). By measuring across these scales, a profile is created to rank

communities from low to high diversity. Once constructed, the profile describes

community structure across scales of diversity (i.e. from species richness [α = 0]

toward evenness [α = ∝]) and allows for ranking and comparing communities by

their profiles. If the profiles cross one another, then they are considered

incomparable and cannot be ranked, but if the one profile is entirely above the

other, then they can be compared and ranked.

In addition, the profiles can be used to describe the influence of rare and

common species. The shape of the profile depends on interrelationships

between richness and evenness for a community (Walker et al. 2003). A profile

that decreases rapidly with increasing scale (α) indicates the presence of rare

species. A profile that decreases slowly indicates more common species and

reflects greater evenness across species in their abundance within the

community.

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The Rènyi diversity index (eq. 1) also has the advantage of being

relatively insensitive to sample size, particularly at larger scales (α). By contrast,

conventional metrics such as Shannon’s Index are known to be downwardly

biased when sample sizes are small (Wilhm 1970; Lande 1996). Rogers et al.

(1999) found Rènyi indices valuable in comparing tree diversity within different-

sized forest areas. Tothmeresz (2003) showed Rènyi estimates to be virtually

insensitive to sample size. The Rènyi index has been used to compare the

diversity of trees, fish and even landscapes, in studies with uneven sampling

intensity (Rogers et al. 1999; Kindt et al. 2006; Carranza et al. 2007). I use the

Rènyi index in this study to compare diversity between two ecoroofs of

substantially dissimilar size.

3.4 Methods

Two dissimilar green roofs were selected, one extensive (site e) and one

intensive (site i). These ecoroofs differed in size, age, structure and appearance

(Table 3.1). Site e consisted of a sedum community established from cuttings in

artificial substrate placed over synthetic sheet material in a nearby grass field

and transplanted 3 months later to the roof as sedum “mats.” Field propagation

occurred in May of 2002 and installation of the green roof occurred in September

of 2002. The substrate consisted of expanded slate, sand, compost, peat, and

dolomite. The depth was less than 7.6 cm. The plant community was a mix of 13

Sedum species. This species composition was maintained post installation by

periodic weeding. Supplemental irrigation was used throughout the growing

season. The roof was 4.2 ha in area and located 9.1 m above ground. The

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immediate context was working industrial with severe historical industrial use.

The larger context was urban metropolis in the Great Lakes Plains Ecoregion.

Descriptors Site e Site i

Visual Features

Class Extensive Intensive

Vegetation Uniform- Forbs (sedums) Polyform- Shrubs, grasses, forbs

Depth >7.5 cm (3") varies 30-60 cm (12"-24") Substrate Engineered mix Amended topsoil Constructed 2002 1987 Elevation 3m (10') 10m (32') Total Size 4.2 Ha (10.4 acres) .14 Ha (.35 acres) Location Dearborn, MI USA Columbus, OH USA Context Industrial Commercial/institutional Ecoregion Great Lakes Eastern Cornbelt Plains

Table 3.1. The two study sites compared by categorical.

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Site i consisted of installed container-grown nursery plants including

Miscanthus spp., Calamagrotis spp., Koeleria spp. (junegrass) and Amelancheir

spp. (serviceberry), and immigrant (naturally colonizing) species. Installation

occurred in 1987. The substrate was amended planting soil. The depth ranged

from 30-60 cm. The original system was designed for supplemental irrigation,

but this failed soon after installation. The plant community was a mix of original

populations and urban pioneering species including Daucus spp. (Queen Anne’s

lace), Chrysanthemum spp. (daisy), and Morus spp. (mulberry). The plant

community was maintained by annual herbicide application for dicot plants and

by hand weeding of any other visually dissimilar plants. The roof was 0.14 ha

and located approximately 2.5 m aboveground. The immediate context was

long-term commercial and institutional land uses. The larger context was urban

metropolis in Eastern Corn Belt Plains Ecoregion.

Motivated by pragmatism, the collection and identification of animal taxa

employed rapid assessment methods. We collected organisms and data from

both sites in a single season using sweep net and observation methods. Four

collecting and observational sessions were conducted on each site during July

through August of 2004. Site e was reduced to an overall collection area of 0.8

ha. Sweep-netting was done along transects in both systems covering the

proportional area of 24.5 m/m2 . The total sample area of site i was 18% of that

on site e. I used a long-handled net with a 40-cm diameter hoop (BioQuip

7328NA). Samples were placed in killing jars, separated, identified and

cataloged. We performed bird observations in 1.5-h sessions prior to

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invertebrate collection. All sightings and behaviors such as foraging were

recorded. Insects were identified as morphospecies within families or

superfamilies, and arachnids within genera. All insect and spider voucher

specimens and sub-samples were reviewed by taxonomic specialists to minimize

splitting and lumping as recommended by Oliver and Beattie (1996b).

Morphospecies are groups of organisms identified as belonging to higher-level

taxa based on their morphological traits (Oliver and Beattie 1996b; Kerr et al.

2000). Birds were identified to species when possible. Taxonomic groups were

combined for analysis and relative abundance was calculated.

Diversity was quantified in two ways. I first used the Rènyi calculation to

compare the two sites (Hill 1973). A diversity profile for each site was

constructed from the Rènyi equation to determine: 1) whether one site clearly

outranked the other in overall diversity and 2) whether the shapes of the Rènyi

curves suggested any clear distinction in community structure. I then calculated

the common diversity indices to provide the more familiar evaluation of

biodiversity. I used the following conventional indices: species richness,

Shannon’s index, Simpson’s index, and eveness. Finally, I also calculated

similarity using Sorenson’s coefficient, and percent similarity. These calculations

used the Ecological Calculator by Oakleaf Systems

(www.oakleafsystems.net/EcoCalc1.html).

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3.5 Results

Insects, spiders and birds were represented within both communities

(Table 3.2). I recorded 59 morphospecies of insects (in 1853 samples), followed

by 9 morphospecies or higher-level groups of spiders and allies in 34 samples,

and 8 species (in 104 samples) of birds. When separated by site and taxonomic

group, highest individual abundances were: Site e- Cicadelliadae (leaf hoppers),

Tetraganthidae (long-jawed orbweavers) and Contopus cooperi (olive-sided

flycatcher), and Site i- Aphidadae (aphids), both Tetraganthidae and Oxyopidae

(lynx spider) and Passer domesticus (house sparrow).

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Table 3.2. Collected Taxa from the two study sites. continued

118

The two insect communities were composed of the same orders, with the

exception that Orthoptera were detected at site e only (Fig. 3.2). Diptera (flies)

were more abundant at this site, while Hemiptera (bugs) and Hymenoptera (due

to the presence of ants, which went unobserved in site e) were more abundant at

site i.

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0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Site e Site i

Rel

ativ

e A

bund

ance

Psocoptera

Orthoptera

Odonata

Hymenoptera

Ephemeroptera

Homoptera

Coleoptera

Hemiptera

Diptera

Figure 3.2. Relative abundance of insect orders at sites e and i.

Diversity was higher in site i across scales of α = 0,1, 2, 3, and 4 (Fig.

3.3). Across all these scales, site i’s profile outranked that of site e. The degree

of similarity between sites was low to moderate. The percent similarity was only

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14.5%; however, Sorenson’s coefficient rated the sites as having moderate

similarity (0.47).

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 1 2 3 4

α

Hs

Figure 3.3. Curves represent diversity Hα (y-axis) of insects, spiders and birds for

both site e (dashed) and site i (solid) across scales α (x-axis), with integer values

of α corresponding to conventional metrics of diversity: 0 (richness), 1

(Shannon’s), 2 (Simpson’s), 3 (Berger-Parker) and 4 (infinity). The curves

indicate higher diversity at site i than site e.

In the next level of analysis, diversity was determined for each taxon at

each site. In addition to the assessment for all taxa, a consistent outranking of

one site over the other emerged for only one of the three taxa (Fig. 3.4). Spiders

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diversity was consistently higher at site i than e (Fig. 3.4 b). Neither insects nor

birds showed a consistent outranking of diversity in one site or the other, as

reflected by the crossing of curves (Fig. 3.4c,d).

Figure 3.4. Diversity profiles describing both site e (dashed) and site i (solid) for:

a) all taxa, b) spiders, c) insects, and d) birds.

3.6 Discussion

Despite the fact that neither ecoroof was constructed to provide habitat

per se, both of them harbored a perhaps surprisingly high diversity of three taxa:

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insects, spiders and birds. The combination of rapid assessment method and the

Rènyi family of diversity indices allowed for apparently meaningful quantitative

descriptions of the diversity of the two ecoroofs. Because wild species inhabited

these ecoroofs, I raise the question as to whether low-quality ecoroof habitat

could create attractive sink habitat, or ecological traps, and consequently

undermine the efforts to conserve wild species.

3.6.1 Combining Rapid Assessment and the Rènyi method for quantifying

diversity

The use of morphospecies allowed for inclusion of invertebrate taxa in the

study. I was able to identify samples as belonging to higher taxonomic levels

using morphological traits. One exception to this was the use of a sub-samples

procedure in the insect analysis, where expert solicitation revealed lumping of

species within the order Diptera. In addition, spider sub-samples contained some

splitting that was corrected by a systematist (as recommended by Oliver and

Beattie 1999a). These methods improved accuracy and allowed for the inclusion

of insects and spiders.

The use of the Rènyi family of diversity indices provided a convenient way

to compare the diversity between the two ecoroofs. The intensive ecoroof has

higher diversity across scales than the extensive ecoroof (Fig. 3.3). However, in

the absence of inferential statistical analysis, interpretation of the curves remains

tentative. Based on Hill (1973) and Walker et al. (2003), I suggest that site i has

more rare species and common species than site e. This pattern is shown when

both lines displays a rapid decline from the scale of α = 0, where rare species are

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more common in site i, to higher scales indicating more common species.

Alternatively, a crossing of the curves would demonstrate that each ecoroof

possessed its own unique pattern. The fact that the curves do not cross

indicates similarity in community structure on the two ecoroofs.

3.6.2 Ecoroof Biodiversity and Conservation

The plant communities on green roofs appear to influence animal

diversity. The prostrate sedum covering in site e creates an environment with

few visual obstructions that is favorable to the olive-sided flycatcher, and the

killdeer, a common gravel roof nester. The olive-sided flycatcher foraged by

perching on protruding skylights 3 m above the ecoroof and making sallies to

capture insects. On the other hand, the high seed-producing ornamental grasses

and densely foliaged berry-producing shrubs in site i are favorable for the urban

species (i.e., house sparrow, northern cardinal, American robin, and gray

catbird). The house sparrow took refuge in the serviceberry shrubs. The higher-

level biodiversity in site i may be explained by the plants of the roof, but other

influences might have contributed to the greater diversity. Jones (2002)

observed that uniform vegetation in extensive ecoroofs can limit diversity. The

use of local soils and substrates of varying depth creates greater variety of plant

architecture, which in turn provides habitat for a greater variety of fauna

(Brenneisen 2003). However, the greater maturity (time since creation) and

closer positioning of site i to the ground may also account for its higher diversity.

These factors of maturity and elevation could influence the use by wild species,

including birds. Many of the urban species such as the sparrow, robin and

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cardinal were observed only on site i. In this case, the roof may act less like an

isolated patch and more like an extension of, or linkage to, the urban context

where multiple species interact. The large presence of adaptable urban birds in

site i could be one indicator of a low quality habitat.

The presence of wild species in both sites is likely to have been influenced

by plant installation methods and maintenance practices. Site e was constructed

by first growing sedum “mats” in a nearby agricultural field. The plants were

started from seeds and cuttings and grown in shallow substrate over plastic

during the growing season. Immigration of plant-feeding insects during that

season probably occurred. In the fall, the mats were cut into 1m2 sections,

relocated to the roof and installed, creating a form of unintended inoculation. This

method of installation could account for the large fly population, if maggots were

relocated in the plant roots during installation. On the other hand, site i was

installed with greenhouse-grown nursery container plants. Both communities are

likely influenced by management practices. Site e included heavy seasonal

irrigation and weekly hand-weeding of all non-sedum vegetation during the

growing season. Site i included annual (summer) spot spraying and cut back

(winter) of all herbaceous plantings.

Currently, attempts to conserve animal biodiversity on ecoroofs are being

advocated without any serious consideration as to whether they may do more

harm than good. Putting an ecoroof in place may often amount to setting an

ecological trap. An ecological trap is a habitat that is “low in quality for

reproduction and survival [that] cannot sustain a population yet…is preferred

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over available, high quality habitats (Donovan and Thompson 2001). In this

scenario, animals make errors in habitat assessment as result of environmental

cues and these errors lead to negative population growth. Donovan and

Thompson (2001), in a simulation study of possible impacts of ecological traps

on migratory birds, found that population growth was most sensitive to adult and

juvenile survival through their habitat selection. When given the choice of high-

quality habitats, populations remained stable, but when low-quality habitat

exceeded 30% of the available area, the population shrank. Because cities

rarely possess high-quality habitat, species may select the lower-quality habitat

in ecoroofs. Their choice can result in reiterative preference for the deceptive

habitat, while attracting other settlers to that same habitat (Swartwout et al.

unpublished results). In a study reflecting this behavior, Baumann (2006)

observed that ecoroofs attracted ground-nesting birds but they suffered low

fecundity in successive years. At this time, we simply do not know whether the

ecoroofs we studied were attractive sinks. Due to the difference in ecoroof

design, habitat quality is likely to vary with each ecoroof increasing the risk of

creating an ecological trap.

It is conceivable that ecoroofs may create suitable, if not ideal, habitat for

wild species. For instance, migratory birds use a variety of stopover habitats in

urban landscapes (Mehlman et al. 2005). These habitats vary in quality and yet

may all provide a valuable ecosystem service. Three types of essential stopover

sites are:1) “fire escape,” 2) “convenience store,“ and 3) ”full service hotel.” The

fire escape and convenience store offer minimal resources and yet may be the

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highest planning priority because they are small remnants near or within large

ecological barriers (like cities) and are often unmanaged. The observations of

the olive-sided flycatcher in site e confirm stopover use on ecoroofs. Thus,

ecoroofs may fill the role of a fire escape or convenient store stopover for some

birds, by providing emergency stopover habitats and furnishing nominal but

necessary resources. As more ecoroofs are created in the city, it is important to

design and construct them in ways that do not set ecological traps but rather

provide suitable habitat.

3.7 Conclusions

First, both types of vegetated roofs provided habitat, regardless of intent. I

found that even in systems constructed without clear conservation objectives

contained wild species of insects, spiders and birds. This conclusion supports

the popular notion of a “field of dreams” approach to building ecoroofs as habitat.

Second, the two systems have distinct species compositions in which over 85%

of species were found to be present in one system and not the other. Third, the

Rènyi family of diversity indices indicated a remarkable degree of similarity in

community structure between the two sites. Diversity was only slightly higher on

the intensive than extensive system, while evenness was similar on the two

roofs. Finally, Tangley (1986) states that ecological investigations in the urban

setting are as valid as those in more pristine environments, but the systems of

study may possess unique ecological processes. Vegetated roof systems may

possess many of these unique processes and so represent an emerging

opportunity for ecological studies. An increase in observation and

127

experimentation is needed as vegetated roof systems continue to be advocated

as a new form of urban habitat.

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in time: The use of Renyi’s generalized entropy function." Ecological Indicators 7(3): 505-510.

Donovan, T. and F. I. Thompson (2001). "Modeling the Ecological Trap

Hypothesis: A Habitat and Demographic Analysis for Migrant Songbirds." Ecological Applications 1(3): 871-882.

Dunnett, N. and N. Kingsbury (2004). Planting Green Roofs and Living Walls.

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Pollution Bulletin 16: p459. Ferraro, S. P. and F. A. Cole (1990). "Taxonomic level and sample size sufficient

for assessing pollution impacts on the Southern California Bight macrobenthos " Marine Ecology Progress Series 67: 251-262.

Gaffin, S., C. Rosenzweig, L. Parshall, D. Hillel, J. Eichenbaum-Pikser, A.

Greenbaum, R. Blake, D. Beattie and R. Berghage (2006). Quantifying evaporative cooling from green roofs and comparison to other land surfaces. In conference proceedings of Greening Rooftops for Sustainable Communities Boston, MA, Green Roofs for Healthy Cities..

Gedge, D. (2003). '...From rubble to Redstarts...' In conference proceedings

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Gedge, D. and G. Kadas (2004). Bugs, bees and spiders: Green roof design for rare invertebrates. In conference proceedings of Greening Rooftops for Sustainable Communities, Portland, OR. Green Roofs for Healthy Cities.

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pitfalls in the measurement and comparison of species richness." Ecology Letters 4(2): 379-391.

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consequences." Ecology 54(2): 427-432. Jones, R. A. (2002). Tecticolous Invertebrates. A preliminary investigation of the

invertebrate fauna on green roofs in urban London. London, English Nature: 36.

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maximise biodiversity in an urban environment. Dept. of Geography. London, University College. MSc Conservation: 76.

Kadas, G. (2006). "Rare Invertebrates Colonizing Green Roofs in London."

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rainforest fragments of the Anamalai Hills, Western Ghats, India." Zoos' Print Journal 21(12): 2483-2488.

Kerr, J. T., A. Sugar and L. Packer (2000). "Indicator taxa, rapid biodiversity

assessment, and nestedness in an endangered ecosystem." Conservation Biology 14(6): 1726-1734.

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Lande, R. (1996). "Statistics and Partitioning of Species Diversity, and Similarity

among Multiple Communities." Oikos 76(1): pg 5-13. Legendre, P. and L. Legendre (1998 ). Numerical Ecology. Amsterdam Elsevier

Science BV. Mehlman, D. W., S. Mabey, D. Ewert, C. Ducan, B. Able, D. Cimprich, R. D.

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Oliver, I. and A. J. Beattie (1996). "Invertebrate morphospecies as surrogates for species: A case study." Conservation Biology 10(1): 99-109.

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Roofs: Forging a New Industry in Canada. Ottawa, ON, Canada Mortgage and Housing Corporation: 54.

Peet, R. (1974). "The measurement of species diversity." Annual Review of

Ecological Systems 5: pgs285-307. Pik, A. J., I. Oliver and A. J. Beattie (1999). "Taxonomic sufficiency in ecological

studies of terrestrial invertebrates." Australian Journal of Ecology 24(3): 555-562.

Poulsen, B. O. and N. Krabbe (1998). "Avifaunal diversity of five high-altitude

cloud forests on the Andean western slope of Ecuador: testing a rapid assessment method." Journal of Biogeography 25(1): 83-93.

Rogers, S. I., D. Maxwell, A. D. Rijnsdorpb, U. Damm and W. Vanhee (1999).

"Fishing effects in northeast Atlantic shelf seas: patterns in fishing effort, diversity and community structure. IV. Can comparisons of species diversity be used to assess human impacts ondemersal fish faunas?" Fisheries Research 40(3): pgs 135-152.

Rosenzweig, M. L. (2003). Win-Win Ecology: How the Earth's Species Can

Survive in the Midst of Human Enterprise. New York, Oxford University Press.

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bandwagon effect: conspecific attraction and vulnerability to ecological traps ".

131

Tangley, L. (1986). "The Urban Ecologist." BioScience 36(2): 68-71. Tinkel, K. C. (1977). Rooftop gardening. Radnor, Pa., Chilton Book Co. Tothmeresz, B. (2003). "Comparison of different methods for diversity ordering."

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CHAPTER 4

EMERGY EVALUTION OF THE PRODUCTIVITY AND SUSTAINABILITY OF

THREE VEGETATED ROOF SYSTEMS

4.1 Abstract

This study used emergy analysis to quantify and compare the

sustainability of three different vegetated roof systems. The study assessed and

compared an agricultural roof garden, a shallow substrate ecoroof, and a deep

substrate ecoroof for flows of energy required for the production of biomass.

Emergy analysis was used to quantify and compare the environmental impacts

and respective benefits of the systems through the fraction renewable, emergy

yield ratio (EYR), environmental loading ratio (ELR) and emergy sustainability

index (ESI). The roof systems were compared to agricultural systems,

constructed landscapes, and a city in order to determine how each system

performed as a sustainable development technology relative to other landscapes.

The shallow substrate ecoroof (ESI = .072) was the most sustainable of the

three, followed by the deep substrate ecoroof (ESI = .03), and lastly the

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agricultural roof garden (ESI = .022). The levels of sustainability were associated

with low percentage usage of renewable resources (extensive 6%, intensive 3%,

agriculture 2%). All three systems were more sustainable than conventional

landscapes, urban gardens and a city while being less sustainable than various

agricultural practices. This study identifies vegetated roof systems with the

greatest non-renewable inputs and makes recommendations to improve the

sustainability of the technology.

4.2 Introduction

Environmental change and diminishing local resources have made

scientists and designers increasingly concerned about urban development.

One goal of sustainable urban development is to build cities that rely on

renewable rather than non-renewable energies and local rather than global

resources. With a goal of increasing the sustainability of buildings and cities,

vegetated roofs systems, or green roofs, are being installed on rooftops in urban

settings (Peck et al. 1999; Dunnett and Kingsbury 2004). However, much of the

materials used in building vegetated roof systems are not locally available, and

require nonrenewable energy inputs to manufacture and transport. Building roofs

with large proportions of non-renewable energies, may compromise the

sustainability of green roofs. To make certain vegetated roof systems are aiding

cities they must be evaluated to determine if the environmental benefits balance

with the resource use and environmental degradation created by their

construction and maintenance. Therefore, this study evaluates the quantities of

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energy and resources used by ecoroofs to improve the understanding of how

these systems impact a city’s sustainable development.

Cities “succeed” due in part to the use of global, or distant, resources that

make cities productive centers. These resources assist in making cities attractive

for living by providing desirable conditions for people. The allocation and

distribution of distant resources demand extensive transportation infrastructure,

which dictates the size and population densities of cities (Mills 1967; Henderson

1974). Another reason cities thrive is because of available energy. Non-

renewable forms of energy, such as coal and gas, are made available to most

cities. Cities converting to renewable forms of energy, such as wind, continue to

require resources. As these energies converge in the city the functions of trade,

government, education and knowledge are created. Once developed these

functions are exported, often times back to the distant resource locations.

Cities experience heightened resource demands as a part of their

increased urbanization. Odum (1971) explained that cities were ‘parasitic’ with

regards to water, air and food. The larger they become, the greater the

proportional cost to the environment. Population increases, combined with

decreasing quality of local resources, create the problems of resource depletion

and environmental degradation, which can result in resource scarcity (Homer-

Dixon 1999). It is projected these problems will increase as 60% of the world’s

population are expected to live in urban areas by 2030 (NRCS 1997).These

problems are caused in part by the conversion of productive agricultural land and

native ecosystems to urban areas, which results in a dependence on global

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markets to provide resources. Cities with a dependence on distant resources

risk long term instability contributing to resource scarcity (Rees and Wackernagel

1996; Holden and Linnerud 2007).

A solution to resource scarcity is the concept of sustainable urban

development. Sustainable development principles imply that in developing land,

resources are balanced with use in space and time to maintain potential to

deliver goods and services to future generations (WCED 1987). Cities can use

renewable energy sources (such as solar and wind) to a small degree, and

employ construction and manufacturing processes that do not compromise the

quality of the natural systems of water and air. Huang and Hsu (2003) explain as

cities use renewable resources and employ self-regulating resource flows they

can better ensure the continued viability of the environments on which they

depend. One construction technology that may contribute to sustainable

development is the practice of roof greening.

Roof greening is the process of growing plants on a building’s rooftop. The

result is called a vegetated roof system. The concept of roof greening uses a

layer of growing medium (soil) and vegetation on rooftops to intercept light and

water to grow plants (Peck et al. 1999). This technology reduces associated

wastes, such as stormwater exports and secondary wastes of carbon (CO2)

created by cooling building structures, while producing oxygen (O2), habitats, and

plant biomass. The environmental benefits of urban plant biomass in vegetated

roof systems have been studied as stormwater retention (Scholz-Barth 2001;

Miller 2003; Rowe et al. 2003), energy reduction (Onmura et al. 2001; Wong et

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al. 2003; Gaffin et al. 2006), habitat creation (Jones 2002; Brenneisen 2005), and

food production (Tinkel 1977). Maximizing these different environmental benefits

has resulted in variation of types among green roof systems.

Two distinct variations of vegetated roofs are ecoroofs and agricultural

roof gardens. Ecoroofs are constructed to retain stormwater, intercept sunlight

and provide habitat. These roofs have variable soil depths and cover the entire

roof surface. The vegetation is usually allowed to self-organize. Maintenance

practices include hand weeding several times a year to eliminate membrane

damaging plants. On the other hand, agricultural roof gardens (roofs designed

specifically for production of food) are intended to reduce the demands for an

imported food supply, making the city more self-reliant by reducing food imports

through local production (Orabon 1990; Allen 1999; Levenston 2002). These

systems involve planting in pots or raised beds containing deep substrates

(soils). They are often built on apartment-building rooftops. Traditional vegetable

garden maintenance practices are employed: improving the soil with organic

matter prior to planting, fertilizing, watering, weeding, and harvesting (Tinkel

1977). The variation between these systems can make assessment and

comparison difficult.

Emergy analysis, which evaluates different systems components on a

common basis, is a promising tool to evaluate resource use and production in

vegetated roof systems. It is a method of environmental accounting where

renewable natural processes and products can be compared on a common basis

with economic processes and products. Emergy analysis has been defined as

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the measure of both the work of nature and of humans in generating products

and services (Odum 1996). This type of analysis puts “the contributions of the

economy on the same basis as the work of the environment” (Odum and Odum

2000). This tool is used as an alternative for determining the net value of

environmental projects to human society. It has been used to evaluate

ecosystems such as wetlands (Howington et al. 1997; Ton et al. 1998),

agricultural farms and farm practices (An 1998; Bastianoni et al. 2001; Rydberg

and Jansén 2002), waste water treatment facilities (Nelson et al. 2001), urban

landscapes in metropolitan areas (Huang et al. 1995; Huang 1998; Huang et al.

2001), and entire regions, such as the state of Maine (Campbell 1998). Brown

and Ulgiati (1997) demonstrated emergy is effective at assessing the

performance of “eco-technologies,” technologies involving natural resources or

ecosystem services. It has been used as a comparative method to measure the

sustainability of some seemingly disparate systems, such as economies, and

some products, such as crude oil and corn, through a series of indices (see

section 5.3.2) (Ulgiati and Brown 1998). More recently, researchers have used

these indices to measure and compare the sustainability of constructed urban

landscapes and agriculture (Beck et al. 2001; Martin et al. 2006)

The goal of this study was to assess three vegetated roof systems with

regard to their resource use, productivity, environmental impact, and overall

sustainability, and compare them to one another and to other constructed

landscapes. The first system was an agricultural roof garden based on a system

in Chicago, Illinois, producing vegetables used to feed the local community. The

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second system was a shallow substrate ecoroof system, based on an ecoroof

simulator system in Columbus, Ohio constructed to retain stormwater and

intercept sunlight. The third was a deep substrate ecoroof based on an ecoroof

simulator system in Columbus, Ohio constructed to retain higher amounts of

stormwater and intercept sunlight. Finally, these systems were compared to

other constructed (non-roof) agricultural or urban landscapes that have been

previously assessed using emergy.

4.3 Methods

4.3.1 Systems Descriptions

The agricultural roof garden was a series of raised beds created on the

top level of a parking garage in an urban neighborhood in Chicago, which

operated for one year (1997). Records on inputs and yields were published for

the Chicago study by Martin (2001). The system consisted of annual plantings

and required seasonal watering, fertilizing, weeding, and harvesting. Plants were

lettuce (Lactuca sativa), spinach (Spinacia oleracea), squash (Cucurbita spp.),

tomato (Lycopersicon esculentum), peppers (Capsicum spp.), onion (Allium

spp.), and cucumber (Cucumis sativis)

The two replicate ecoroofs were constructed one meter above the ground

on a crushed stone nursery pad at the Ohio State University agricultural farm,

Columbus, Ohio, USA, in the spring of 2004. These systems simulated ecoroofs

and contained nine shallow plots 10 cm deep and nine deep plots 30 cm deep.

All the plots were sized at 1m2. They were planted once with Little blue stem

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(Schizachyrium scoparium) and Low grow sumac (Rhus aromatica ‘Gro Low’).

Maintenance practices involved weeding once a year for woody plants with

membrane-penetrating roots.

Quantities of all inputs were recorded for one year for the agricultural roof

garden and a measure of vegetable biomass was taken at harvest. For both

ecoroofs all input quantities were recorded over two years to determine annual

biomass. Ecoroof plants were harvested in the second year for each system.

Data from both of these systems was extrapolated to represent a 98m2 area to

equal that of the agricultural roofs. The renewable inputs used the regional

values of Chicago for sun, wind, and rainfall distribution. In addition, membrane

inputs were equated. Membrane inputs for agricultural systems were made to

conform to the national standards of roof greening systems by including drainage

and root protection membranes. The assessment is based on thirty-year

duration due to the life expectancy of the water-proofing membrane.

4.3.2 Emergy Flows and Definitions

Emergy analysis is based on the flow of the following resource inputs

(Figure 5.1-5.4); Renewable resources (R), such as sun wind and rain; Non-

Renewable resources (N), which are the local energy stores within the system,

such as topsoil in a farm system; and Purchased resources (F), which are the

inputs containing human investment, such as equipment, construction materials,

and services, including labor. Inputs interact in the system and produce a yield. A

Yield (Y) is equal to the sum of all inputs (Y = R+N+F). The detailed flow is

illustrated in the emergy diagrams of the vegetated roof systems (Fig 4.1-4.3).

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The inputs on the left of the system (sun, wind, and rain) are the renewable

resources. Those on the top are the purchased resources; some examples

include plants, membranes, topsoil, fertilizers, irrigation and labor. The absence

of non-renewable inputs (N) in each of the vegetated roof systems was found.

Therefore, the soils are shown as storage that was imported as a purchased

input. Tables 4.1 and 4.3 denote the specific flows that comprise the resources.

The flows of resources are converted to emergy through transformities which

have been calculated for a wide variety of resources and renewable energies.

They can be found in past publications, articles and dissertations (Odum 1996;

Burnakarn 1998; Odum et al. 2000; Bastianoni 2001; Brown and Bardi 2001;

Brandt-Williams 2002; Huang and Hsu 2003; Ganeshan 2005). An additional

analysis was performed to determine the emergy of expanded clay material used

in the extensive and intensive ecoroofs (See section 4.4).

The emergy analysis tables (Tables 4.1 and 4.3) were directly constructed

from the diagrams (Fig. 4.1-4.4), using inflows and outflows crossing the system

boundary as row headings. Within each table, the annual amount of input or

output of each flow is quantified in raw units (joules, grams, dollars). The next

column is the transformity value, which was multiplied by the raw units resulting

in the third column, annual solar emergy of each flow (Appendix III).

Definitions for terms regarding emergy (Ulgiati and Brown 1998)

• Emergy: The available energy of one kind that is used in the

transformation directly and indirectly to make a product or service. Emergy

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is measured in emjoules. Sunlight, fuel, electricity and human service and

all other resource flows can be put on a common basis by expressing

them in solar emjoules (sej)

• Solar emjoules: The units of solar energy previously used to generate a

product or service. One solar emjoule (sej) equals one joule (J) of sunlight.

• Transformity: The ratio obtained by dividing the total emergy that was

used in a process by the energy yielded as output. This is used to convert

different types of energies to emergy. It is expressed as solar emjoules

per joule (sej/J).

• Specific emergy: The emergy per unit of mass output. This is usually

expressed as solar emergy per gram (sej/g-1).

Emergy indices compare flows from the economy to flows of the

environment. Through these measurements, net yields can be compared to

environmental loads. Measuring sustainability through emergy analysis indicates

if a process provides a suitable yield contribution to the user with a low

environmental pressure. This can be used to measure the resource use,

environmental impact and sustainability of the construction, and operation, of an

agricultural roof garden and determine if these systems provide a suitable

contribution to the urban environment. The one modification being that non-

renewable inputs (N) were omitted from the calculations because they were not

present in the examined systems. The indices and their descriptions used here

have been provided by Ulgiati and Brown (1998).

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Emergy Indices

• Emergy Yield Ratio (EYR): The ratio of exported emergy to emergy that is

invested as purchased inputs. It measures the ability of the system to

exploit renewable resources.

EYR = Y/F

• Environmental Loading Ratio (ELR): Ratio of purchased and non-

renewable resources to renewable resources. This indicates the pressure

of a system on the surrounding environment.

ELR = F/R

• Sustainability Index: The ratio of the emergy yield ratio to the

environmental loading ratio. It measures the production of a system

relative to the environmental pressure.

ESI = EYR/ELR

4.3.3 Emergy Analysis

The methodology for the emergy analysis began with the organization of

the three systems diagrams (Fig. 4.1-4.3) and the recording of flows (Table 4.1).

Omitted from this study were the resources used in the building structures where

the systems were constructed. However, start-up costs are included in

purchased resources as machinery and a one-time labor input. The annual plant

growth and labor occur in a 181-day growing season. All of the vegetated roof

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systems inputs were spread equally across thirty years based on the longevity of

the waterproofing materials.

The renewable inputs (R) of sun, wind, and rain, were the same for each

of the systems (Table 4.1). The renewable inputs are not accumulated to avoid

double counting. Due to the interdependency of these inputs on the same

energies, the largest input is chosen as the sum of these inputs (Odum 1996)

(Table 4.1). The largest input in this category, the chemical potential of rain, was

calculated by multiplying the annual rainfall for the area of the roof garden by the

transformity value for the chemical potential of rainfall (Table 4.1).

The purchased resources varied between the agricultural roof garden and

the two ecoroofs. The purchased inputs of the agricultural roof garden included

plants, protective membranes (waterproofing, drainage and root barrier), topsoil,

compost, irrigation, fertilizer (nitrogen, phosphorus and potassium), machinery

and labor (Fig. 4.1). For the two ecoroofs the input categories were similar. The

purchase inputs for the two ecoroofs included plants, protective membranes

(waterproofing, drainage and root barrier) expanded clay, irrigation, sand,

compost, machinery and human labor (Fig 4.2 and 4.3). For all three systems

labor represents start-up and annual maintenance (Fig 4.1-4.3).

The emergy inputs for plants for the three systems were calculated based

on their costs in dollars. The dollar values were multiplied to previously

calculated emergy/dollar ratios for the year 1997. The emergy/dollar ratio

measures the emergy associated with each US dollar and was calculated by

dividing the annual United States inflow of emergy by the Gross National Product

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particular to that year. (Ulgiati et al. 1994). All plants for the agricultural roof

garden were installed annually at the beginning of the growing season creating

an annual cost over thirty years, while the ecoroof plants were installed once

during start-up (Table 4.1 and Appendix III). All membrane quantities were based

on area and chemical composition. The agricultural roof system was made to

conform to the national standards of roof greening systems by adding drainage

and root protective membranes. All loose materials including topsoil, expanded

clay, sand, and compost were calculated by volume and density. The agricultural

roof topsoil included 30% organic material, so only 5% by volume (compost) was

added to the topsoil (Table 4.1, 4.2 and Appendix C). The compost was

calculated as topsoil with an organic fraction of 0.5 as performed by Ganeshan

(2005). The expanded clay required a sub-analysis because the literature lacked

a transformity or specific emergy for the material (See section 4.4). The ecoroof

substrate was calculated as a composition of 70% expanded clay: 20% compost:

10% sand as provided by the manufacturer (Table 4.2) The values for irrigation

of the agricultural roof garden were calculated as annual potable water

requirement of terrestrial vegetable crops in Illinois minus rainfall, assuming the

balance of water would be added during dry periods (Table 4.1 and Appendix C).

For the ecoroofs, irrigation was calculated for thirty days of use for plant

establishment and then discontinued. Fertilizer used was an annual starter

fertilizer every year, and the value was estimated based on coverage as

recommended (O.S.U. 1997). Machinery for all roofs was the machinery and

tools needed for start-up and operation, although the majority was for start-up.

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Machinery is not used in maintenance operations, and tools are rarely used

because they are potential hazards to the protective membranes.

For the agricultural roof garden, labor was calculated as 3.5 hour per day

over the growing season. This allowed for all labor activities, including planting,

weeding, fertilizing, watering, and harvesting (3.5 hr/day *178days=622hrs/yr)

(Ebenezer 2003). Labor for the ecoroof systems was based on the routine

maintenance practice of three days per year (8 hrs/day *3=24hrs/yr) (Dunnett

and Kingsbury 2004) (Table 5.1 and Appendix III). Additionally, a one-time

figure was added to labor for start up costs, including planning, design, and

installation for each system. It assumed 80 hours for 15 weeks (1200hrs) at a

technician rate (4.30E+12 sej/hr), (Oretga 2000) . The extensive roof figure was

reduced by 20% to account for lower quantity of installed growing material.

The system output was vegetable yield (edible biomass) and whole plant

(dry weight) biomass for the agricultural roof garden, and whole plant (dry weight)

biomass for the ecoroofs. Recording different weights to represent food and

ecological services allows for disciplinary comparison. The total annual harvest

of fresh material from the agricultural roof for 1997 was recorded to be 446.1 kg

(Ebenezer 2003). The ratio of edible biomass to whole plant was 4:1 creating

557.6 kg total whole plant biomass (Stockert et al. 2000). The fresh weight was

multiplied by the dry weight ratio of 0.08 from Thornley et al. (1981) and Jung et

al. (2004). The biomass for the ecoroofs was harvested from the ecoroof

simulator as whole plant biomass dried at 55oC for 72 hours and weighed. The

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weight for the extensive ecoroof was 10.98 kg/yr and the intensive ecoroof was

29.16 kg/yr (Table 5.1 and Appendix III).

Figure 4.1. The emergy system diagram of the agricultural roof garden. Inputs to

the system (circles) are quantified in Table 4.1 corresponding to the number

shown. Interactions occur within the system boundary (larger rectangle) and

outputs leaving the system are shown as arrows.

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Figure 4.2. The emergy system diagram of the shallow substrate ecoroof. Inputs

to the system (circles) are quantified in Table 4.1 corresponding to the number

shown. Interactions occur within the system boundary (larger rectangle) and

outputs leaving the system are shown as arrows.

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Figure 4.3. The emergy system diagram of the deep substrate ecoroof. Inputs to

the system (circles) are quantified in Table 4.1 corresponding to the number

shown. Interactions occur within the system boundary (larger rectangle) and

outputs leaving the system are shown as arrows.

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ITEM RAW UNITS EMERGY per UNIT

EMERGY Transformity Source

(sej/unit) (sej) Renewable resources 1 Sunlight 4.62E+12 J 1.00E+00 4.62E+12 Odum 1996 2 Wind 3.54E+11 J 1.50E+03 5.31E+14 Odum1996 3 Rain 1.32E+11 J 1.82E+04 2.41E+15 Odum 1996 Purchased Resources Agricultural Roof Garden 4 Plants 2.59E+03 $ 1.37E+12 3.55E+15 Odum1996 5 Waterproofing (PVC) 2.86E+05 g 5.87E+09 1.68E+15 Buranakarn 1998 6 Drainage fabric (PE) 7.45E+04 g 5.76E+09 4.29E+14 Buranakarn 1998 7 Root membrane (HDPE) 2.72E+04 g 5.27E+09 1.43E+14 Buranakarn 1998 8 Topsoil* 2.96E+11 J 7.40E+04 2.19E+16 Odum1996 9 Compost 1.11E+11 J 7.40E+04 8.21E+15 Odum1996 10 Irrigation 8.88E+05 Gal 7.30E+09 6.48E+15 Buenfil 1999 11 Nitrogen 4.08E+03 g 1.74E+09 7.10E+12 Odum1996 12 Phosphorus 5.43E+03 g 4.60E+09 2.50E+13 Odum1996 13 Potassium 4.08E+03 g 1.78E+10 7.26E+13 Odum1996 14 Machinery 3.05E+03 $ 1.37E+12 4.18E+15 Odum1996 15 Labor 1.99E+04 hr 4.30E+12 8.54E+16 Ortega 2000 16 Output (edible biomass) 1.33E+07 g 1.32E+17 17 Output (whole plant) 1.66E+07 g 1.32E+17 Shallow Substrate Ecoroof 18 Plants 1.86E+03 $ 1.37E+12 2.55E+15 Odum1996 19 Waterproofing (PVC) 2.86E+05 g 5.87E+09 1.68E+15 Buranakarn 1998 20 Drainage fabric (PE) 7.45E+04 g 5.76E+09 4.29E+14 Buranakarn 1998 21 Root membrane (HDPE) 2.72E+04 g 5.27E+09 1.43E+14 Buranakarn 1998 22 Expanded clay 4.99E+06 g 3.04E+09 1.52E+16 from this study 23 Irrigation 9.85E+03 Gal 7.30E+09 7.19E+13 Buenfil 1999 24 Sand 2.29E+06 g 1.12E+09 2.56E+15 Odum 1996 25 Compost 1.45E+11 J 7.40E+04 1.07E+16 Odum 1996 26 Machinery 1.95E+03 $ 1.37E+12 2.67E+15 Odum1996 27 Labor 1.70E+03 hr 4.30E+12 7.31E+15 Ortega 2000 28 Output 2.14E+05 g 4.33E+16 Deep Substrate Ecoroof 29 Plants 1.86E+03 $ 1.37E+12 2.55E+15 Odum1996 30 Waterproofing (PVC) 2.86E+05 g 5.87E+09 1.68E+15 Buranakarn 1998 31 Drainage fabric (PE) 7.45E+04 g 5.76E+09 4.29E+14 Buranakarn 1998 32 Root membrane (HDPE) 2.72E+04 g 5.27E+09 1.43E+14 Buranakarn 1998 33 Expanded clay 1.50E+07 g 3.04E+09 4.56E+16 from this study 34 Irrigation 9.85E+03 Gal 7.30E+09 7.19E+13 Buenfil 1999 35 Sand 4.55E+06 g 1.12E+09 5.10E+15 Odum 1996 36 Compost 3.06E+11 J 7.40E+04 2.26E+16 Odum 1996 37 Machinery 2.80E+03 $ 1.37E+12 3.84E+15 Odum1996 38 Labor 1.92E+03 hr 4.30E+12 8.26E+15 Ortega 2000 39 Output 5.68E+05 g 9.03E+16

Table 4.1. The emergy table of the vegetated roof systems quantifies inputs and

outputs from raw units, which are multiplied by the emergy per unit (transformity)

to get a total emergy value for each input. Output is the sum of the all emergy

values.

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ITEM UNIT AGRICULTURAL ROOF GARDEN (%) EXTENSIVE

ECOROOF (%) INTENSIVE ECOROOF (%)

Topsoil m3 29.71 (0.95) - -

Compost m3 1.51 (0.05) 1.98 (0.2) 4.16 (0.2)

Expanded clay m3 - 6.94 (0.75) 20.8 (0.75)

Sand m3 - 0.99 (0.1) 1.98 (0.1)

Table 4.2. Substrate composition table of the three vegetated roofs systems by

volume and percentage per cubic meter.

4.4 Sub-analysis of expanded clay

4.4.1 The emergy analysis of expanded clay

The material transformity of expanded clay in the shallow and deep

ecoroof systems was not found and therefore required a sub-analysis. Expanded

clay is lightweight aggregate produced by the thermal expansion of clay bodies

through a rotary kiln (EPA 1993). The analysis of this process is based on the

emergy analysis of similar construction materials performed by Burnakarn

(1998). The information was provided by contributors to the Expanded Shale,

Clay and Slate Institute and is based on the operations of a sponsor facility

(ESCSI 2004). The process as described by the individual facility was compared

to current publications (Aineto et al. 2004; Pioro and Pioro 2004).

An emergy diagram was constructed to assess the flows of resources in

the process (Fig. 4.4). The process includes only purchased inputs and services

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(F) of clay, natural gas, coal, machinery, fuels and labor (Table 5.3). The

expanded clay did not possess any renewable inputs (R) (Fig. 5.4). All inputs

were based on annual quantities used by the facility. Natural gas and coal were

used to operate the facility and the kiln. The machinery component included the

kilns, trucks and sorting equipment. Fuels were used for transportation. The labor

was based on hours of work by the numbers of employees used to operate the

facility.

The output of the process was 2.70E+10 g, while the Yield was 7.88E+19

sej (Table 4.4). The specific emergy for expanded clay was determined by

dividing the Yield (Y) by the amount of materials produced as explained by Odum

(1996). The specific emergy for expanded clay was 3.04E+09 sej/g. This value is

higher than concrete block at 3.54E+08 sej/g, brick at 2.22E+09 sej/g (Burnakarn

1998), and steel at 2.16E+09 sej/g (Odum 1996), but lower than fertilizer at

3.8E+09 sej/g (Odum 1996), and aluminum at 1.74E+10 sej/g (Lagerberg and

Brown 1999).

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Figure 4.4. The emergy system diagram of expanded clay. . Inputs to the system

(circles) are quantified in Table 4.1 corresponding to the number shown.

Interactions occur within the system boundary (larger rectangle) and outputs

leaving the system are shown as arrows.

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ITEM RAW UNITS EMERGY per UNIT EMERGY Transformity Source

Purchased Resources

1 Clay 3.60E+10 g 2.00E+09 7.20E+19 Odum 1996

2 Natural gas 1.87E+07 g 4.80E+04 8.98E+11 Buranakarn 1998

3 Coal 7.90E+13 g 4.10E+04 3.24E+18 Odum 1996

4 Machinery 4.10E+08 g 5.27E+09 2.16E+18 Buranakarn 1998

5 Fuel 2.39E+06 g 1.32E+08 3.16E+14 Brandt-Williams 2002

6 Labor 3.31E+05 hr 4.30E+12 1.42E+18 Ortega 2000

7 Output 2.70E+10 g 7.88E+19

Table 4.3 Emergy table of expanded clay quantifies inputs and outputs from raw

units, which are multiplied by the emergy per unit (transformity) to get a total

emergy value for each input. Output is the sum of the all emergy values.

4.5 Results

4.5.1 Renewable

The renewable resource entering all systems with the largest emergy was

rain at 2.41E+15 sej (see Table 4.1). Wind was within one order of magnitude of

the rain (5.31E+14 sej). The sun possessed the lowest value of all renewable

flows (4.62E+12 sej). Because these were given as regional inputs, they were

identical for all three systems.

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4.5.2 Purchased Resources

The emergy inputs in all three systems were the highest in the area of

purchased resources when compared to renewable inputs. Across all systems,

the imported resources of labor, growing medium (topsoil or expanded clay),

plants, and compost were the larger inputs in this category. Labor in the

agricultural roof garden recorded the highest of all inputs in any system at

8.54E+16 sej (Table 5.1). The large amount of emergy was due both to the

amount of labor imported (1.99E+04 hr) and the transformity of this resource

(4.30E+12 sej). This input accounted for 65% of all the purchased inputs in the

agricultural roof garden. Topsoil was the second greatest input to the agricultural

system at 16% (2.19E+16 sej). The third was the compost, which accounted for

6% (8.21E+15sej). Irrigation and machinery accounted for 5% each, and sand

and plants for 3% each. Collectively, the protective membranes accounted for

1.6%. Lastly, fertilizers accounted for 1% or less of the total.

In the shallow substrate ecoroof, the expanded clay, which constituted

part of the growing material, was the largest input (1.52E+16 sej) due to its

quantity (4.99E+06 g) and the specific emergy (3.04E+09 sej/g, Table 5.1) of the

resource. This accounted for 35% of all purchased inputs. Compost, which was

mixed with the expanded clay, was the second major input for the extensive roof

at 25% (1.07E+16 sej). The third was human labor at 17% (7.31E+15 sej).

Machinery, sand, and plants each accounted for 6% of the purchased resources.

Collectively, the protective membranes accounted for 5%. Lastly, irrigation

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accounted for less than 1% because it was used only for one season during plant

establishment.

In the deep substrate ecoroof, the inputs from the growing materials of

expanded clay and compost accounted for the majority of the purchased

resources. Expanded clay accounted for 50% of all the purchased inputs

(4.56E+16 sej, Table 4.1). This was due to its quantity (1.50E+07 g). Compost

accounted for the second greatest input at 26% (2.24E+16 sej). Following those

two larger inputs were labor at 9%, sand at 5%, and machinery at 4%.

Collectively, the protective membranes accounted for 2%. Lastly, irrigation

accounted for less than 1%.

Due to the large emergy inputs from labor, topsoil and compost, the

purchased emergy was greatest for the agricultural roof garden (1.32E+17 sej,

Table 4.1). The deep substrate ecoroof had the second greatest input of

purchased resources, 9.03E+16 sej, or 73% of that of the agricultural roof garden

(Table 4.1). The shallow substrate ecoroof had the lowest input of purchased

resources, at 32% of the agricultural roof garden resources (4.33E+16 sej, Table

4.1).

4.5.4 Yields and Specific Emergy

The system yield was calculated by totaling the renewable, non-

renewable, and purchased inputs. In the agricultural roof garden, the system

yield was 1.34E+17 sej (Table 4.4) and the biomass output, the amount of

vegetables produced, was 1.33E+07g, which resulted in the specific emergy of

1.01E+10 sej/g (Table 4.3). The yield of the branched outflow of the whole plant

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in the agricultural roof remained 1.34E+17 sej and the biomass output, the

amount of plant biomass produced, was 1.66E+07g, which resulted in the

specific emergy of 9.92E+10 sej/g. The system yield for the shallow substrate

ecoroof was 4.57E+16 sej (Table 4.1) and the biomass output was 2.14E+05 g.

This resulted in a specific emergy of 2.14E+11 sej/g for the shallow ecoroof. The

system yield for the deep substrate ecoroof was 1.04E+17 sej/g and the biomass

output was 5.68E+05 g, which resulted in a specific emergy of 1.84E+11 sej/g

(Table 4.4).

4.5.5 Emergy Indices

Each of the three systems used very low amounts of renewable resources

when compared to purchased resources. The fraction of renewable inputs for

each system were 0.02 (agricultural roof garden), 0.06 (shallow substrate

ecoroof), and 0.03 (deep substrate ecoroof) (Table 4.4). This indicates that no

system used more than 6% of renewable resources in order to operate. The

shallow ecoroof used the most at 6%, while the agricultural roof was the lowest

and used only 2%. The emergy yield ratio was greatest in the shallow ecoroof

(1.06), while the agricultural roof garden and deep ecoroof both recorded the

score of 1.02 (Table 4.3). The environmental loading ratio was the highest in the

agricultural roof garden (45) and lowest for the shallow ecoroof (15) (Table 4.4).

The emergy sustainability index was the highest for the shallow ecoroof (7.17E-

02), followed by the deep ecoroof (2.96E-02), with the lowest being the

agricultural roof garden (2.27E-02) (Table 4.4).

Result DESCRIPTION

CALCULATION AGRICULTURAL ROOF GARDEN

AGRICULTURAL ROOF GARDEN *

SHALLOW SUBSTRATE ECOROOF

DEEP SUBSTRATE ECOROOF

Biomass edible harvest fresh wt. whole plant dry wt. whole plant dry wt. whole plant dry wt.

Specific Emergy (sej/g) 1.01E+10 9.92E+10 2.14E+11 1.63E+11

Renewable emergy inputs (R) (sej) Figure 4.1-4.3 2.95E+15 2.95E+15 2.95E+15 2.95E+15

Non renewable input (N) (sej) Figure 4.1-4.3 0 0 0 0

Imported emergy inputs (I) (sej) Figure 4.1-4.3 1.32E+17 1.32E+17 4.33E+16 9.03E+16

Yield (Y) (sej) (R+N+I) 1.34E+17 1.34E+17 4.57E+16 9.27E+16

Fraction Renewable R/(R+N+I) 0.02 0.02 0.06 0.03

Emergy Yield Ratio (EYR) (Y/I) 1.02 1.02 1.06 1.03

Environmental Loading Ratio (ELR) (I+N/R) 45 45 15 31

Sustainability Index (ESI) (EYR/ELR) 2.27E-02 2.27E-02 7.17E-02 3.35E-02

* The branched flow measuring whole plant dry weight.

Table 4.4. Emergy indices table describing the three vegetated roofs systems and branched flow of the agricultural

roof garden.

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4.6 Discussion

4.6.1 Limitations

Vegetated roof systems have various outputs, however, only biomass was

assessed. The reasons to assess biomass (productivity) in ecoroofs are: 1)

productivity is linked to other ecosystem functions, such as biodiversity and

community stability (Naeem et al. 1996), 2) productivity appears to affect the

environmental benefits of energy, habitat, and stormwater runoff provided by

ecoroofs (Wong et al. 2003; Brenneisen 2004; Rowe et al. pending), and 4)

advocates in the public realm are currently proposing productivity as a way to

maximize environmental benefits in ecoroofs (Mankiewicz and McDonnell 2006).

Although many studies provide information on other environmental benefits few

report findings with measurable outputs. For example, storm water retention has

been recorded, but there are very few reporting evapotranspiration, which would

be the measurable output of the hydrological cycle (Lipton and Strecker 2003;

Rowe et al. 2003; Hunt and Smith 2005). Another example is wildlife studies are

beginning to record species presence and diversity (Brenneisen 2003), but

studies investigating dispersal could not be found. By recording whole plant

biomass, I am trying to indirectly account for these benefits; however, this is an

underestimation of the total benefits from the system. The limitation of not

accounting for these individual outputs is lower overall output and a higher

specific emergy for each system. For example, the output for evapotranspiration

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and dispersal when summed with the output of biomass could increase the

system’s total output. When included, these outputs would lower the specific

emergy, or transformity, of each vegetated roof system. Equally, systems

characteristics such as greater water storage in the deep substrate ecoroof may

allow for increased evapotranspiration compared with the shallow substrate

ecoroof, thus improving the system’s total output of one roof over another.

The location of the system’s boundary may impact the measure of

performance and sustainability. The boundary was placed at the roof level.

Expanding this boundary may affect performance. Beck et al (2001) noted

limitations that plot level studies may have an effect on the values of constructed

landscapes. When the system boundary included the residential house,

resources such as labor could be reallocated with effects on sustainability. The

labor, or a portion of it, would no longer be considered a purchased input but

instead renewable. In vegetated roof systems for instance, individuals living and

working in the building with an agricultural roof garden and providing the required

labor for the garden could reduce the need for purchased labor inputs. This

would reduce the environmental loading ratio and improve the emergy

sustainability index based on the proportion of food resources used in supporting

the individuals. However, widening the boundary may have the reverse impacts

on performance. Carter and Rasmussen (2005) found that scale changes

impacted ecoroof performance in stormwater. Performances of vegetated roof

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systems were considered less effective in sparsely developed watershed when

compared to their studies using just the ecoroof as a boundary.

4.6.2 Vegetated Roof Systems Sustainability and Productivity

Although definitions of sustainability differ, Brown and Ulgiati (1997)

explain that sustainability is a function of yield, renewability and load on the

environment. Therefore, a system that produces a negative net yield by

definition, cannot be sustained without continual flows of purchased emergy.

Equally, if a system relies on non-renewable resources and places an extreme

load on the environment, it threatens any long term operation. Assuming this

interpretation, each of the examined vegetated roof systems operate with a low

level of sustainability because of their dependence on purchased inputs for yields

and high loads on the environment. The variation of in each vegetated roof

system input quantities contributed to a range of sustainability of the systems.

Of the three systems, the shallow ecoroof possessed a greater level of

sustainability because it used a greater percentage of renewable inputs

compared to those of purchased inputs (Table 4.4). The higher emergy

sustainability index value of the shallow ecoroof (7.17E-02 Table 4.4), was

because the system used twice the percentage of renewable inputs (6%) than

the deep ecoroof (3%) and two-thirds more than the agricultural roof garden

(2%). This is reflected in the environmental loading ratios which have direct

inverse relationships to the fraction renewable (Ulgiati and Brown 1998). The

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shallow ecoroof had a lower environmental loading ratio (15) than the agricultural

roof garden (45) and the deep ecoroof (35). Another way of understanding this

relationship is the degree of sustainability that was shown to be a reciprocal to

the level of purchased inputs. The shallow ecoroof had the highest sustainability

and the lowest amounts of purchase inputs, while the agricultural roof garden

recorded the lowest sustainability and the highest amounts of purchased inputs.

The growing media and labor were the inputs most influencing the level of

sustainability.

Contributing to the higher sustainability of the shallow ecoroof was the

lower input use of growing medium (2.85E+16 sej) than both the agricultural

(3.01E+16 sej) and intensive (8.50E+16 sej). Additionally, the shallow ecoroof

system operated with the lowest input of labor at 7.31E+15 sej compared to the

deep (8.26E+15 sej) and the agricultural (8.54E+16 sej). The high level of labor

input for the agricultural roof garden was due to manual labor of annual planting,

hand watering, and seasonal harvesting. In the intensive ecoroof, labor was

higher because of greater initial start-up inputs.

Due to the purchased inputs vegetated roof systems do not operate like

natural systems. Ulgiati and Brown (1998) state that natural systems commonly

have ELR = 0 when operating on 100% renewable inputs. Tilley and Swank

(2003) showed that managed natural systems, such as forest reserves used for

timber, recreation, and conservation, received up to 49% of their emergy from the

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natural resources of precipitation, wind, and sunlight. Therefore, vegetated roof

systems cannot be considered ‘natural’ with renewable inputs below 6%.

Of the three systems the agricultural roof was the most efficient at

producing biomass for food and environmental services. The specific emergy of

the agricultural roof (edible biomass) was 1.10E+10 sej/j. This demonstrates the

benefits of investing in higher quality energies such as labor, fertilizers and

irrigation. These energies improve production efficiencies in the roof. However,

these efficiencies were not as good as those observed by Martin et al (2006) in

the conventional corn and blackberry farms. When adjusted to a comparable unit,

corn (4.29E+08 sej/g/ha) had a lower specific emergy than blackberries

(4.83E+08 sej/g/ha), while both were lower than the agricultural roof. Therefore,

the agricultural roof was not as productive as conventional farming. On the other

hand if the investment in higher quality inputs in the agricultural roof does not

compromise environmental services, then the system can produce greater

regulatory services than the other roofs as well. The roof generates more whole

plant biomass at a lower transformity (9.92E+10 sej/g) (Table 4.5). This means

the agricultural roof could cool the building structure or reduce runoff with more

efficiency than ecoroofs due to its productivity.

4.6.3 Comparison to other landscape systems

In order to better understand the vegetated roof systems, they were

compared to other constructed landscapes previously assessed using emergy

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(Table 4.5). When compared to landscapes that either produce food or are

constructed as part of urban settings, vegetated roof systems recorded middle

range values of ratios and indices. Compared with traditional and conventional

agriculture, all three vegetated roof systems recorded lower emergy yield ratios

and higher environmental loading ratios resulting in lower emergy sustainability

index values. On the other hand, compared to a city, constructed urban gardens

and a conventional landscape the three systems showed higher emergy yield

ratios and lower environmental loads, which resulted in higher emergy

sustainability index values (Table 4.5). The three vegetated roof systems

possess ESI of 0.07 (shallow ecoroof), 0.03 (deep ecoroof), and 0.04

(agricultural roof garden). All roof systems had lower sustainability than

indigenous farming in Chiapas, Mexico (ESI of 115), a local farm in Italy (1.75), a

blackberry farm in the USA (0.65), a local vineyard in Italy (0.44) and a

conventional corn farm in the USA (0.06). All agricultural systems had higher

emergy yield ratios and lower environmental loading ratios than the roof systems.

Therefore, the vegetated roof systems had lower sustainability due to the lower

yields and higher pressures on the environment. However, all vegetated roof

systems have higher sustainability than a conventional landscape (8.61E-06), an

organic garden (0.002), an edible landscape (0.002), a forest garden (0.001) and

the city of Taipei, China (0.001). All of the urban landscapes possessed lower

emergy yield ratios and higher environmental loading ratios. Therefore,

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vegetated roof systems had greater levels of sustainability due to higher yields

and lower pressures on the environment.

The entire group of constructed urban systems, including vegetated roof

systems, possessed low levels of sustainability as shown by their low emergy

sustainability index scores. This should be of concern to not only the designers of

vegetated roof systems, but also to all professions involved with practices of

creating urban landscapes and urban ecological systems. Beck et al (2001)

noted these results were due to the cumulative emergy investment for almost all

items that were brought into the system for establishment. The establishment of

vegetated roof systems is similar to these landscapes; however, less purchased

resources are added and they operate more efficiently. Beck et al (2001)

continued to show that the conventional landscape possessing a lawn is one of

the most unsustainable constructed urban systems. Comparatively, conventional

landscapes would further reduce the already low levels of the sustainability of a

city such as Taipei. The vegetated roof systems recorded much higher levels of

sustainability (0.07, 0.03, and 0.02) when compared to the conventional

landscape (8.61E-06) and gardens (0.002-0.001). This means that vegetated

roof systems would be a more sustainable choice in the city to provide food or

environmental services than a conventional landscape and urban gardens.

The vegetated roofs systems seem to operate similarly to constructed

urban landscapes such as gardens. Beck et al (2001) noted that the low emergy

yield ratios and the emergy sustainability were due to high levels of purchased

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resources from the economy. This was reflected in their high environmental

loading ratio. The addition of materials and labor to prevent unwanted plants

(weeds) from damaging either the aesthetic quality or productivity of the gardens

created higher environmental loads for the gardens. One difference is that

vegetated roof systems operate more efficiently by importing less purchased

resources and being freer from demands of weed competition and aesthetics.

SYSTEM LOCATION RENEWABLE NON-RENEWABLE PURCHASE

D FRACTION RENEWABLE EYR ELR ESI

R (sej) N (sej) F (sej) R/(R+N+F) (Y/F) (F+N/R) (EYR/ELR)

Results

Extensive Ecoroof Ohio, USA 2.95E+15 0.00E+00 4.57E+16 0.06 1.06 15 0.07

Intensive Ecoroof Ohio, USA 2.95E+15 0.00E+00 9.27E+16 0.03 1.03 31 0.03

Agricultural Roof Garden Illinois, USA 2.95E+15 0.00E+00 1.34E+17 0.02 1.02 45 0.02

Comparisons

Indigenous Farm1 Chiapas, Mexico 1.37E+06 3.57E+15 3.23E+15 0.91 12.17 0.10 116

Local Farm2 Chianti, Italy - - - - 1.96 1 1.75

Blackberry Farm1 Ohio, USA 2.66E+15 0.00E+00 5.93E+15 0.31 1.45 2.23 0.65

Local Vinyard2 Chianti, Italy - - - - 1.79 4 0.44

Conventional Corn Farm1 Kansas, USA 6.56E+14 2.16E+14 1.21E+16 0.05 1.07 18.80 0.06

Edible Landscape2 Ohio, USA 2.28E+13 3.03E+12 2.50E+13 - 0.28 138 0.002

Organic Garden2 Ohio, USA 2.28E+13 3.03E+12 2.58E+13 - 0.38 210 0.002

Forest Garden2 Ohio, USA 2.28E+13 4.50E+11 2.33E+13 - 0.28 221 0.001

City of Taipei 2002 4 Taiwan - - - - 1.13 695 0.001

Conventional Landscape3 Ohio, USA 2.28E+13 3.40E+11 2.31E+13 - 9.92E-04 115 8.61E-06

References for comparison: 1. Martin et al 2006, 2. Bastianoni 2001, 3. Beck et al 2001 and 4. Huang and Chen pending

Table 4.5. Comparative landscapes table describes the values of the three vegetated roof systems and ten

previously evaluated landscapes.

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4.6.3 The City and Vegetated Roof Systems

All three vegetated roofs systems (0.07-0.02) were found to be more

sustainable than the city of Taipei (0.001). Each vegetated roof system

possessed higher emergy yield ratios and lower environmental loading ratios

(Table 4.5). Cities like Taipei import energy and resources such as petroleum,

coal, steel and lumber as well as services, such as information and banking,

creating a high environmental loading ratio (695). Taipei also uses

hydroelectricity, a renewable input, as well as local non-renewables, such as coal

and topsoil. This improves the higher emergy yield ratio compared to vegetated

roofs. However, the greater use of renewable and local non-renewable resources

is not enough to offset the large amounts of purchased resources. Although, the

vegetated roofs systems use very little renewable resources they have much

lower environmental loads compared to the city. The combination of these makes

for a system that operates with improved sustainability. This means adding any

of the vegetated roof systems to the city of Taipei would improve its

sustainability.

Vegetated roof systems can improve urban sustainability, but only if they

depend on renewable inputs, do not increase purchased inputs and are built in a

highly urban setting that has a low ESI. Huang and Chen (2005) explain that as

cities urbanize they lose self-sufficiency as they convert from natural areas to

urban infrastructure. As imported energies converge in the city there is a decline

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of natural areas and a loss of biomass and biomass storage. As a result nearby

agricultural and natural resources must be used to support the city center.

Because vegetated roof systems produce biomass, they can perform particular

environmental services that regional resources would otherwise have to provide.

The roof systems can in part manage stormwater and temperature regulation and

create habitat and food locally. However, the assumption is made that biomass

in the city operates from renewable inputs. Lastly, Huang and Shih (1992)

explain as communities urbanize there is a decrease in their emergy

sustainability index. This would mean that vegetated roof systems would have

greater impact in the improvement of a city’s sustainability, if the setting is largely

urban, or urbanizing. On the other hand, vegetated roof systems would have the

opposite effect in a city that is less urban or possesses a higher ESI. In this case,

a vegetated roof would have the opposite effect lowering the sustainability of the

city. This makes the contributions of any vegetated roof system dependent on

the level of sustainability of the city.

4.6.4 The Perception of the Vegetated Roof Technology

The vegetated roof systems assessed in this study performed contrary to

current perception. Most vegetated roof systems are expected to operate with a

high level of sustainability. Instead, the vegetated roof systems operated only

with more sustainability than other constructed landscapes. Vegetated roof

systems did not use enough renewable energies to be considered highly

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sustainable. A more apt description of the current technology is that they are a

less unsustainable choice for the city than conventional landscape and

constructed gardens. This is due to start-up installation as well as maintenance.

Beck et al (2001) show that labor and materials used to tend the garden were

large inputs that would continue in order to create and maintain the landscape

aesthetics and harvest the produce. They state that the sustainability of a

conventional landscape and gardens appears not to be strongly related to time,

but rather the investment of purchased inputs. Because ecoroofs import less

materials and services than conventional landscapes they are more sustainable.

One important advantage of vegetated roof systems, especially ecoroofs,

is they are constructed systems possessing no universal aesthetic, which could

offer a high potential for a naturalized aesthetic (Dunnett 2006). Allowing roof

system vegetation to self-organize post construction could effectively reduce

labor inputs. Although natural aesthetics on vegetated roof systems have been

said to be ‘out-of-place’ in the urban environment (Wayland-Smith 2005), the

reduction of associated labor may be necessary to improve the high

environmental loads of the systems.

4.6.5 Improved Sustainability

To improve system sustainability the construction of new systems should

consider finding ways to improve yield, use proportionately more renewable

resources, and alleviate the high inputs of purchased resources that have been

170

associated with these systems. This would allow vegetated roofs to improve the

sustainability in more settings. The use of growing media (topsoil, expanded clay

and compost) is one area to consider because it was the largest input for both

ecoroofs (>65%) and the second largest input for the agricultural roof (>20%).

Most contemporary vegetated roof systems use imported soil-less media made

from expanded lightweight aggregate (Schundler 2002). If the systems used

topsoil instead, which was stockpiled during construction for later use on the roof

top, a system could potentially reduce purchased inputs. A sensitivity analysis,

which halved the soil inputs affected the intensive ecoroof the most by increasing

the percent renewable by 66%, decreasing the ELR by 49% and subsequently

increasing the ESI by 94%. The others showed the same pattern to a lesser

degree. Additionally, structural support may be required to support a on-site

topsoil, which is heavier than expanded clay. This could be justified if the

structural improvements are minor, because the specific emergy of expanded

clay (3.04E+09 sej/g) is higher than concrete at 1.44E+09 sej/g (Burnakarn 1998)

and steel at 2.16E+09 sej/g (Odum 1996). Because substrate is so often studied

in this technology, this area shows promise for reducing the purchased inputs of

vegetated roof systems. Actions to reduce the environmental loading ratio in the

systems by using on-site topsoil would allow for a reduction in the ratio.

Reallocating this resource as local and re-calculating for wind erosion of the

materials would add non-renewable inputs, but potentially be a net reduction in

the environmental loading ratio. Gedge (2003) has shown that on-site topsoil can

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be used in constructing an extensive ecoroof. Additionally, local topsoil has been

shown to improve biodiversity (Brenneisen 2003). Post- construction practices

recommend wind erosion protection in the form of coir sheets spread over the

substrate surface (Peck and Kuhn 2001), yet more publications recording the

rates of erosion would be needed for calculations.

Another recommendation for the agricultural roof garden to reduce

irrigation inputs is to recycle the stormwater. Recycling stormwater in vegetated

roof system is being increasingly experimented and proposed (Compton and

Whitlow 2006; Shirley-Smith 2006). The input of planting of seeds, instead of

starter plants, may also reduce the inputs of labor in all systems. Lastly, if the

compost were generated on site as a part of the construction process, inputs

may be further reduced. By reducing all of the purchased inputs, the

environmental loading ratio would decrease and improve the emergy

sustainability index.

To aide a city’s level of sustainability vegetated roof systems must be

considered at the scale of the building or city. Huang and Chen (2005) conclude

that waste generation and treatment must be considered in the urban setting

through circular resource flows. Vegetated roof systems are particularly suited for

inter-urban circular flows. The recycle of both stormwater as well as moderate

amounts of building composted wastes could be utilized in vegetated roof

systems. Kula (2005) has shown that even small area vegetated roof systems

can treat building wastes. Also, the reduction of energy use from air conditioning

172

due to vegetated roof systems has been shown (Onmura et al. 2001; Alcazar and

Bass 2005). From the scale of the city, like Taipei, which uses renewable

sources, labor can become a renewable input. In the first stages of the

technology, skilled labor and knowledge are imported as purchased resources.

Overtime the knowledge can be stored locally and reused in a skilled workforce.

When this transition happens the systems use less purchased resources.

4.7 Conclusions

Emergy analysis allowed for the assessment of sustainability of three

vegetated roof systems and the comparison of those systems to other

landscapes. Overall, vegetated roof systems use relatively low percentages of

renewable inputs when compared to purchased inputs. In their current form they

use very little local resources. The dependence on purchased inputs creates low

levels of sustainability in each of the vegetated roof systems. To improve system

sustainability vegetated roofs should be constructed with on-site topsoil, built with

recycled irrigation and composting systems, and consider the current level of

sustainability of the city.

The shallow substrate ecoroof was more sustainable than the deep

substrate ecoroof. Both ecoroofs were more sustainable than the agricultural

ecoroof. This was due to larger amounts of purchased inputs of substrate

(topsoil) and labor in the deep substrate ecoroof and agricultural roof garden.

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In comparison to other constructed urban landscapes, vegetated roof

systems were shown to be more sustainable than a conventional landscape,

urban gardens and a city, but far from the level of sustainability of local and

indigenous agricultural practices. The similarity of all the constructed landscapes,

the city and vegetated roofs lies in the reliance on purchased energy flows. This

means that improving the sustainability of a city with vegetated roof systems is

dependant upon the urbanizing condition of the city, the percent of renewable

inputs used in vegetated roof systems, and other factors affecting the

construction and maintenance of the systems such as aesthetic demands.

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APPENDIX A

VEGETATED ROOF SYSTEM DESCRIPTIONS

Ford Motor Plant

Location: Deaborn Mi, USA Owner: Ford Motor Company Building Architect; William McDonough + Partners Ecoroof Designer: McDonough and Braungart, Xero flo Ecoroof Contractor: na Year of construction: 2003 Area of ecoroof: 41,806 m2 Substrate type: lightweight aggregates, sand and organic material Substrate Depth: 7.0 cm Weight: 11lbs/ft2 Plant installation: sedum mats Ecoroof Researchers: Don Russell, Reid Coffman, Topics of Research: energy, hydrology, plant coverage, biodiversity

GAP

Location: San Bruno, CA, USA Owner: Gap, Inc. Building Architect: William McDonough + Partners Ecoroof Designer: Hargreaves & Associates w/Paul Kephart, Rana Creek Ecoroof Contractor: Swinerton Year of construction: 1997 Area of ecoroof: 6410 m2 Substrate type: engineered growing medium Substrate Depth: 15.2 cm

194

Weight: na Plant installation: plugs/pots . Ecoroof Researcher: Stephan Brenneisen Topics of Research: biodiversity- plant and invertebrate species richness, energy, productivity

Latter Day Saints Conference Center

Location: Salt Lake Center, UT USA Owner: Church of Latter Day Saints Architect: Simmer Gunsel Frasca Partnership, Ecoroof Designer: Olin Partnership, Landscape Architect Ecoroof Contractor: KPFF Year of construction: 2000 Area of ecoroof: 32,326 m2 Substrate type: expanded aggregate and organic material Substrate Depth: 5.08 -121.1 cm Weight: na Plant installation: various, seed (prairie) to containers (trees) Ecoroof Researcher: na Topics of Research: stewardship- use counts and personal testimony, plant survival

Long Island (Green) City Location: Long Island City, Queens, New York USA Owner: varies Building Architect: varies Ecoroof Designer: Balamori Associates Ecoroof Contractor: varies Year of construction: 2005+ Area of ecoroof: 2.6 Km2 Substrate type: na Substrate Depth: 7.6-15.2 cm Weight: na Plant installation: Sedums Ecoroof Researcher: Earth Pledge Topics of Research: hydrology and energy

Mountain Equipment Co-op Location: Winnipeg, Ontario Canada Owner: Winnipeg Mountain Equipment Co-op Building Architect: na Ecoroof Designer: Design Solutions Ecoroof Contractor: na

195

Year of construction: 2003 Area of ecoroof: na Substrate type: lightweight aggregates, sand and organic material Substrate Depth: 20.1 cm Weight: na Plant installation: plugs/pots Ecoroof Researchers: Richard Kula Topics of Research: hydrology, plant biodiversity

Multnomah County Building

Location: Portland, OR USA Owner: County of Multnomah Building Architect: na Ecoroof Designer: Macdonald Environmental Planning Ecoroof Contractor: na Year of construction: 2002 Area of ecoroof: 1114 m2 Substrate type: lightweight aggregates, sand and organic material Substrate Depth: 15.2 cm Weight: 30lbs/ft2 Plant installation: seed, fescue and wildflowers, sedum, and ornamental grass Ecoroof Researchers: Portland State University, Macdonald Engineering Topics of Research: hydrology- runoff and water budgets

Sechelt Justice Building

Location: Sechelt, British Columbia Canada Owner: City of Sechelt Building Architect: (retro-fit) project architects Carleton Hart Ecoroof Designer: Sharp and Diamond Landscape Architecture Ecoroof Contractor: na Year of construction: 2002 Area of ecoroof: na Substrate type: lightweight aggregates, sand and organic material Substrate Depth: 7.62 cm Weight: 30lbs/ft2 Plant installation: plugs/pots Ecoroof Researchers: na Topics of Research: na

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Rossetti Location: Basel, Switzerland Owner: City of Basel Building Architect: Jaques Herzog & Peirre De Meuron Ecoroof Designer: Stephan Brenneisen Ecoroof Contractor: Biber Dach Year of construction: 1998 Area of ecoroof: 1500 m2 Substrate type: local topsoil of sandy loamy gravel. Substrate Depth: 7-30cm Weight: na Plant installation: seed- Basel forbs and herbs. Ecoroof Researcher: Stephan Brenneisen Topics of Research: biodiversity- plant and invertebrate species richness, energy, productivity

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APPENDIX B

STATESTICAL ANALYSIS

Source DF Seq SS Adj SS Adj MS F P Class 1 31958 31958 31958 236.02 0.000 Alternative 2 3344 3344 1672 12.35 0.000 Plant 1 36443 36443 36443 269.15 0.000 Class*Plant 1 4727 4727 4727 34.91 0.000 Error 30 4062 4062 135 Total 35 80533 S = 11.6362 R-Sq = 94.96% R-Sq(adj) = 94.12%

Table B.1: ANOVA (General Linear Model) for whole plant biomass (per plant per plot) versus class, alternative, plant

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Source DF SS MS F Value Pr>F Model 3 40.50000000 13.50000000 15.75 <.0001 Error 14 12.00000000 0.85714286 Corrected Total 17 52.50000000 R-Square Coeff Var Root MSE rankbio2 Mean 0.771429 26.45200 0.925820 3.500000 Source DF Type I SS Mean Square F Value Pr > F class 1 40.50000000 40.50000000 47.25 <.0001 Source DF Type III SS Mean Square F Value Pr > F class 1 40.50000000 40.50000000 47.25 <.0001

Table B.2: ANOVA (Friedman’s) for biomass (per plot) amongst class Source DF SS MS F Value Pr>F Model 3 81.0000000 27.0000000 9.69 0.0010 Error 14 39.0000000 2.7857143 Corrected Total 17 120.0000000 R-Square Coeff Var Root MSE rankbio Mean 0.675000 33.38092 1.669046 5.000000 Source DF Type I SS Mean Square F Value Pr > F alt 2 81.00000000 40.50000000 14.54 0.0004 Source DF Type III SS Mean Square F Value Pr > F alt 2 81.00000000 40.50000000 14.54 0.0004

Table B.3: ANOVA (Friedman’s) for biomass (per plot) amongst alternative Source DF Seq SS Adj SS Adj MS F P Storm Qnty 1 1.40683 1.24007 1.24007 62.23 0.000 Class 1 1.85008 1.85008 1.85008 92.84 0.000 Alternative 3 0.83636 0.83795 0.27932 14.02 0.000 Storm Type 1 0.00283 0.00283 0.00283 0.14 0.707 Year 1 0.76751 0.76751 0.76751 44.95 0.000 Error 263 5.24080 5.24080 0.01993 Total 269 9.33690 S = 0.141163 R-Sq = 43.87% R-Sq(adj) = 42.59%

Table B.4: ANOVA (General Linear Model) for Retention

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Source DF Seq SS Adj SS Adj MS F P Date 7 0.676083 0.676083 0.096583 181.72 0.000 Class 1 0.008138 0.008138 0.008138 15.31 0.000 Alternative 3 0.018531 0.018531 0.006177 11.62 0.000 Error 180 0.095669 0.095669 0.000531 Total 191 0.798420 S = 0.0230541 R-Sq = 88.02% R-Sq(adj) = 87.29%

Table B.5: ANOVA (General Linear Model) for Electrical Conductivity Source DF Seq SS Adj SS Adj MS F P Date 7 3.35661 3.35661 0.47952 8.69 0.000 Class 1 0.00130 0.00130 0.00130 0.02 0.878 Alternative 3 2.27182 2.27182 0.75727 13.72 0.000 Error 180 9.93646 9.93646 0.05520 Total 191 15.56620 S = 0.234952 R-Sq = 36.17% R-Sq(adj) = 32.27%

Table B.6: ANOVA (General Linear Model) for pH

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Appendix C

EMERGY CALCULATIONS

Calculations Renewable Resources

1 Sunlight (area) (insolation) (albedo) (duration) (transformity) roof container area = 98.0 m2 insolation = 4.12E+09 J/m2 (www.solarelectric.com) albedo = .36 (Martin) Transformity = 1sej/J (by defintion) (98.0 m2) (0.36) (1sej) (30 yrs) (1054.8 m2) (4.12E+09 J/m2/yr) (4.63E+12 J) (1sej) 4.63E+12

2 Wind

(area) (density) (eddy diffusion coefficeint) (wind gradient)(duration)(transformity)

roof container area = 98 m2 ht. = 50 m density = 1.23 kg/m3 eddy diffusion coefficient = 14.74 m2/s wind gradient = .00442/s transformity = 1.50E+03 sej/J (Odum, 1996)

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(98 m2 )(50 m)(1.23 kg/m3)(14.74 m2/s)(.00442/s)(31540000 s/yr)(30yrs) (3.54E+11)(1.50E+03sej/J) 5.31E+14

3 Rain Chemical Potential (area) (rainfall) (G)(duration)(transformity) roof container area = 98 m2 rainfall = .908 m/yr G = 4.94 (Gibbs free energy of evaportranspiring plants) transformity = 1.82E+04 (Odum, 1996) (98 m2 )(.908 m/yr)(4.94G)(1E+06g/m3)(30yrs) (1.32E+11)(1.82E+04 sej/J) 2.40E+15

Purchased Resources Agricultural Roof Garden

4 Plants Vegetable starter plants purchased from local retail store. (amount)(duration) (transformity) amount = $35+3%/yr transformity = 6.30E+12 (Odum 1996) (35 $+3%/yr)(30yr) (1594$)(6.30E+12sej/$) 1.00E+16

5 Waterproofing (PVC) (amount)(duration)(transformity) amount = 1.8E+05 g transformity = 5.87E+09sej/g (Buranakarn, 1998) (1.8E+05 g/yr )(1yr) (1.8E+05 g/yr ) (5.87E+09sej/g) 1.06E+15

6 Drainage fabric (Plastic) (amount) (Transformity) amount = 75450g transformity = 5.76E+09sej/g (Buranakarn, 1998) (74450g)(5.76E+09sej/g) 4.28E+14

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7 Root membrane (HDPE) (amount) (Transformity) amount = 27162g transformity = 5.27E+09sej/g (Buranakarn, 1998) (27162g)(5.27E+09sej/g) 1.44E+15

8 Topsoil (Volume of material)(density)(organic fraction) (G) (duration) (transformity) volume = 29.71 m3 fraction organic = .30 g/g density = 1.47E+06 g/m3 transformity = 7.4E+04 sej/J (Odum 1996) (1.47E+06 g/m3)(.30g/g)(5.4 Kcal/g)(4186 J/kcal) (29.71 m3) (9.96E+08 J/m3)(1yr) (2.96E+11J) (7.4E+04 sej/J) 2.19E+16

9 Compost (Volume of material)(density)(organic fraction) (G)(duration)(transformity) volume = 1.51 m3 density = 6.50E+06 g/m3 Organic Fraction = .50 g/g transformity = 7.4E+04 sej/J (Odum 1996) ( 1.51 m3)(6.50E+06 g/m3) (1yrs)(.50g/g)(5.4 Kcal/g)(4186 J/kcal) = (1.10E+11J) (7.4E+04 sej/g) 8.21E+15

10 Irrigation Potable water use as needed from local spicket. Amount = (Requirement)(time)(% from rainfall) (area)(duration)(transformity) requirement = .0127m/day time = 180 days % from rainfall= 50% area = 98m2 duration = 30yrs amount = 29594 gal/yr or (112m3) transformity of potable water = 7.30E+09 gal/yr (Bunefil, 2001) (29594/yr )(30yrs) (8.87E+05 )(7.30E+09 gal/yr)

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6.48E+15

11,12,13 Fertilizer Starter Fertilzer of 10-20-10 applied at commerical rate of 120lbs per acre. (amount)(duration)(transformity) Amounts = 136 g N; 181 g P; 136 g K

transformity = 1.74E+09 sej/g N; 4.6E+09 sej/g P; 17.8E+09 sej/g K (Odum, 1996)

(136g/yr)(30yrs); (181g/yr)(30yrs);(136g/yr)(30yrs) (4080g)(1.74E+09 sej/g);(5430g)(4.6E+09 sej/g);(4080g)(17.8E+09 sej/g) (7.09E+12) + (2.49E+13) + (27.26E+13) 1.04E+14

14 Machinery (amout in dollars) (duration)(transformity) Amount = crane $2700 + tools $350 amount = $3050 transformity = 1.37E+12 sej/hr (Odum 1996) ($3050)(1.37E+12sej/hr) 1.48E+15sej

15 Labor (amout in dollars) (duration)(transformity) labor = 622hr/yr transformity = 4.30E+12 sej/hr (Ortrega 2002) (622hr/yr)(30yr) + (1200hr) (19860hr)(4.30E+12sej/hr) 8.54E+16

Output 16 Output - Vegetable Biomass

(amount)(duration) (4.42E+05 g/yr) (30yr) 1.33E+07 g

17 Output - Vegetable Biomass (amount)(duration)

(4.98E+08 g/yr) (30yr) 1.66E+07 g

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Purchased Resources Extensive Ecoroof

18 Plants (amount) (duration) (transformity) amount = $1862 transformity =1.37E+12 sej/g (Odum 1996) ($1862) (1yr) (1.37E+12 sej/g) 2.55E+15

19 Waterproofing (PVC) (amount)(duration)(transformity) amount = 1.8E+05 g transformity = 5.87E+09sej/g (Buranakarn 1998) (1.8E+05 g/yr )(1yr) (1.8E+05 g/yr ) (5.87E+09sej/g) 1.68E+15

20 Drainage fabric (Plastic) (amount)(duration)(transformity) amount = 75450g transformity = 5.76E+09sej/g (Buranakarn 1998) (74450g)(1yr) (74450g)(5.76E+09sej/g) 4.29E+14

21 Root membrane (HDPE) (amount)(duration)(transformity) amount = 27162g transformity = 5.27E+09sej/g (Buranakarn 1998) (27162g)(1yr) (27162g)(5.27E+09sej/g) 1.44E+14

22 Expanded clay (Volume of material) (density)(duration)(transformity) volume = 6.94 m3 density = 7.2E+05 g/m3

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transformity =2.86E+09sej/g from this study (6.94m3)( 7.2E+05 g/m3)(1yr) (4.99E+06g)(2.86E+09sej/g) 1.43E+16

23 Irrigation Potable water use as needed from local spicket. Amount = (Requirement)(time)(area)(duration)(transformity) requirement = .0127m/day time = 30 days area = 98m2 amount = 9853.6 gal/yr or (37.3m3) transformity of potable water = 7.30E+09 gal/yr (Bunefil, 2001) (9853.6gal/yr )(1yr) (9853.6 gal/yr )(7.30E+09 sej/gal) 7.19E+13

24 Sand (Volume of material)(density)(transformity) volume = .99 m3 density = 2.3E +06 g/m3 transformity = 1.12E+09 sej/g (Odum 1996) (.99 m3) (2.3E+06 g/m3) (2.28E+06g)(1.12E+09 sej/g ) 5.10E+15

25 Compost (Volume of material)(density)(organic fraction) (G)(duration)(transformity) volume =1.98 m3 density = 6.50E+06 g/m3 Organic Fraction = .50 g/g transformity = 7.4E+04 sej/J (Odum 1996) (1.98 m3)(6.50E+06 g/m3) (1yrs)(.50g/g)(5.4 Kcal/g)(4186 J/kcal) = (1.45E+11g) (7.40E+04 sej/g) 1.07E+16

26 Machinery (amout in dollars) (duration)(transformity) Amount = crane $1800 + tools $150 amount = $1950

206

transformity = 1.37E+12 sej/hr (Odum 1996) ($3050)(1.37E+12sej/hr) 1.48E+15sej

27 Labor (amount) (duration)(transformity) + (start-up) labor = 24hr/yr transformity = 4.30E+12 sej/hr (Ortrega 2002) (24h/yr)(30yr) + (980hr) (1700hr)(4.30E+12sej/$) 4.24E+16

Output 28 Output - Whole Plant Biomass

(amount)(area)(duration) (72.8 g/m2/yr) (98m2) (30yr) 2.14E+05 g

Purchased Resources Intensive Ecoroof

29 Plants (amount) (duration) (transformity) amount = $1862 transformity =1.37E+12 sej/g (Odum 1996) ($1862) (1yr) (1.37E+12 sej/g) 2.55E+15

30 Waterproofing (PVC) (amount)(duration)(transformity) amount = 1.8E+05 g transformity = 5.87E+09sej/g (Buranakarn 1998) (1.8E+05 g/yr )(1yr) (1.8E+05 g/yr ) (5.87E+09sej/g) 1.68E+15

31 Drainage fabric (Plastic) (amount)(duration)(transformity) amount = 75450g

207

transformity = 5.76E+09sej/g (Buranakarn 1998) (74450g)(1yr) (74450g)(5.76E+09sej/g) 4.29E+14

32 Root membrane (HDPE) (amount)(duration)(transformity) amount = 27162g transformity = 5.27E+09sej/g (Buranakarn 1998) (27162g)(1yr) (27162g)(5.27E+09sej/g) 1.44E+14

33 Expanded clay (Volume of material)(density)(duration)(transformity) volume = 20.8 m3 density = 7.2E + 5 g/m3 transformity =2.86E+09sej/g from this study (20.8m3)(7.2E+05 g/m3)(1yr) (1.50E+07g) (2.86E+09sej/g) 4.28E+16

34 Irrigation Potable water use as needed from local spicket. Amount = (Requirement)(time)(area)(duration)(transformity) requirement = .0127m/day time = 30 days area = 98m2 amount = 9853.6 gal/yr or (37.3m3) transformity of potable water = 7.30E+09 gal/yr (Bunefil, 2001) (9853.6gal/yr )(1yr) (9853.6 gal/yr )(7.30E+09 sej/gal) 7.19E+13

35 Sand (Volume of material)(density)(transformity) volume = 1.98 m3 density = 2.3E +06 g/m3 transformity = 1.12E+09 sej/g (Odum, 1996) ( 1.98 m3)(2.3E+06 g/m3)

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(4.55E+06g) (1.12E+09 sej/g ) 5.10E+15

36 Compost (Volume of material)(density)(organic fraction) (G)(duration)(transformity) volume =5.94 m3 density = 6.50E+06 g/m3 Organic Fraction = .50 g/g transformity = 7.4E+04 sej/J (Odum 1996) (5.94 m3)(6.50E+06 g/m3) (1yrs)(.50g/g)(5.4 Kcal/g)(4186 J/kcal) = (4.63E+11g) (7.40E+04 sej/g) 3.43E+16

37 Machinery (amout in dollars) (duration)(transformity) amount = crane $2700 + tools $150 amount = $2850 transformity = 1.37E+12 sej/hr (Ortrega 2002) ($2850)(1.37E+12sej/hr) 1.48E+15sej

38 Labor (amount) (duration)(transformity) + (start-up) labor = 24hr/yr transformity = 4.30E+12 sej/hr (Ortrega 2002) (24h/yr)(30yr) + (1200hr) (1920hr)(4.30E+12sej/$) 4.43E+16

Output 39 Output - Whole Plant Biomass

(amount)(area)(duration) (193.3 g/m2/yr) (98m2) (30yr) 5.68E+05 g

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APPENDIX D

PERMISSION TO USE COPYRIGHTED MATERIAL

March 14, 2007 Reid R. Coffman Doctoral Candidate The Ohio State University Re: Copyright request Mr. Coffman, Green Roofs for Healthy Cities authorizes, Reid R. Coffman, permission to use the following GRHC copyrighted materials for the purpose of dissertation submittal at The Ohio State University, and the subsequent microfilming by ProQuest/UMI. Coffman, R. (2007). Comparing wildlife habitat and biodiversity across green roof type. In the

conference proceedings of Greening Rooftops for Sustainable Conference, Minneapolis MN, Green Roofs for Healthy Cities.

Coffman, R. and G. Davis (2005). Insect and Avian Fauna Presence on the Ford River Rouge

Green Roof. In the conference proceedings of Greening Rooftops for Sustainable Conference, Washington DC, Green Roofs for Healthy Cities.

Coffman, R. and J. F. Martin (2004). The Sustainability of An Agricultural Roof Garden. In the

conference proceedings of Greening Rooftops for Sustainable Communities, Portland, OR, Green Roofs for Healthy Cities.

Regards, Jennifer Sprout Director, Conferences and Events Green Roofs for Healthy Cities Telephone: 416-971-4494 E-Mail: jsprout@greenroofs.org