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Energy and Buildings 88 (2015) 122–134

Contents lists available at ScienceDirect

Energy and Buildings

j ourna l ho me pa g e: www.elsev ier .com/ locate /enbui ld

hermal performance analysis of an emergency shelter using dynamicuilding simulation

ristina Cornaroa,b,∗, Dalila Saporia, Francesco Buccia, Marco Pierroa,orrado Giammancoc,b

Department of Enterprise Engineering, University of Rome Tor Vergata, Via del Politecnico, 1, 00133 Rome, ItalyCHOSE, University of Rome Tor Vergata, Via del Politecnico, 1, 00133 Rome, ItalyDepartment of Electronic Engineering, University of Rome Tor Vergata, Via del Politecnico, 1, 00133 Rome, Italy

r t i c l e i n f o

rticle history:eceived 31 July 2014eceived in revised form8 November 2014ccepted 20 November 2014vailable online 26 November 2014

eywords:

a b s t r a c t

This work has the purpose to analyze thermal performance of emergency shelters with the aim to developdifferent solutions which can improve the internal environmental conditions, in accordance to the param-eters that describe thermo-hygrometric comfort, to the materials of which they are generally made ofand to the climatic conditions under which they may be exposed. The object of the study was a tentequipped with a photovoltaic system produced by CHOSE (Center for Hybrid and Organic Solar Energy)at the University of Rome Tor Vergata. Through the use of the software IDA Indoor Climate and Energy4.5, a simulation model was built based on experimental data collected from May 7 to May 15, 2013;

helterhermal comfortynamic building simulationhermal performance

model calibration was carried out comparing the simulation with the experimental data and the modelwas used for the formulation of different improvement solutions. The shelter model was analyzed in twodifferent Italian climatic conditions using climatic data from Torino (winter) and Palermo (summer). Thesuggested optimization solutions were proven to be useful to improve the indoor climate and energyneeds of the unit. The procedure can be applied to various climatic conditions and to different locations.

. Introduction

It is known that the occurrence of various natural disasters couldorce the affected population to leave their homes. In these casest is necessary to provide temporary housing settlements to cope

ith such a request.This study is focused on the analysis of one of the multiple solu-

ions of intervention used in certain situations: the field tent.Tents are in fact the most frequently used emergency housing

ypology because they are easy to carry and assemble but at thexpense of very bad indoor living conditions, which depend on dif-erent issues related to the various types of climatic zones in whichhey are installed.

It appears important to underline that the basic purpose of each

ype of shelter is to offer better indoor climatic conditions or at leastifferent from those which characterize the external environment;hen this is not achieved, it is easy that prolonged exposure of

∗ Corresponding author at: Department of Enterprise Engineering, University ofome Tor Vergata, Via del Politecnico, 1, 00133 Rome, Italy. Tel.: +39 0672597233;

ax: +39 0672597233.E-mail address: cornaro@uniroma2.it (C. Cornaro).

ttp://dx.doi.org/10.1016/j.enbuild.2014.11.055378-7788/© 2014 Elsevier B.V. All rights reserved.

© 2014 Elsevier B.V. All rights reserved.

occupants to environmental conditions, sometimes extreme, couldbe fatal to their health.

From these observations comes the need for shelters to retainheat when they are installed in geographical areas subject to lowtemperatures. Conversely, in case of hot climates and high humid-ity, the shelters must be able to expel the heat that builds up in itduring the day.

This paper wants to explore the performance of a tent exposed tohot and cold climates at the mid latitudes. Through a dynamic sim-ulation model built in the IDA ICE 4.5 environment and calibratedusing data collected during a short term monitoring campaign car-ried on in May 2013 near Rome, it was possible to understand theissues of the different examined cases and to try to improve internalhousing conditions and energy efficiency with the use of insulat-ing materials together with the employment of heating and coolingsystems.

2. Previous studies

Over recent years, a number of international research labo-ratories have turned their attention to the study of the internalconditions of some temporary shelters used by various humani-tarian organizations in emergency situations. The researches were

nd Buildings 88 (2015) 122–134 123

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arried out in order to evaluate the characteristics and quality ofndoor environments which depend on different issues related tohe various climatic zones in which they were installed. However,he works on this topic are quite few in the literature.

Research carried out on these topics by Dr. Regan Pantangaroa ofedR [1] (Australian Humanitarian Agency for International Emer-encies), starts right from the processing of climate data that thearious areas of intervention may arise from time to time; theseesults can be obtained directly by on site measurements but theyan also be deduced from the prevailing topographic conditions.his approach is oriented to a passive design, a design that makesse of natural and free resources (like wind) to get comfortable

ndoor living conditions. For example, in arid climates, natural ven-ilation has proved to be one of the few useful solutions to improveiving conditions of the displaced, because it contributes positivelyo the air exchange and then to the heat escape. In case of coldlimates, instead, it is appropriate to place shelters perpendicularo the main wind direction, thus avoiding the icy currents withinhem. Anyway it appears that, below 7 ◦C, there is no possibility tose only a passive design to achieve comfort conditions, but a directeating intervention must be used.

These studies also highlight the fact that the curtains are gen-rally made up of fabrics such as cotton which, because of theirigh porosity, allow the leakage of indoor air. Indeed these tissues,aving high values of thermal conductivity, have poor insulationapabilities and the heat produced inside is quickly dissipated byonduction. This phenomenon is responsible for the great waste ofnergy when using air conditioning systems.

Ajam [2] carried out a study of thermal comfort in low-cost,dobe refugee shelters in arid climates on behalf of United Nationelief and Works Agency (UNRWA) for Palestine and Near East.

Since 1998, Manfield [3] of The Martin Centre for Architecturalnd Urban Studies, Cambridge University, led a series of experi-ents on temporary shelters for emergencies in cold climates. For

is purposes he made use of wind tunnel, environmental chambersnd field tests to obtain the useful physical parameters and also tohose some criteria for results evaluation, useful to develop a newrototype of tent: these are cost, weight, volume, time for assemblynd, not least, thermal comfort.

There are several military research laboratories, such as the oneed by Flanders [4], that conducted several tests on military shelters,ransportable by air, paying particular attention to thermal effi-iency, thus aiming to reduce the use of fuel and have an effectiveontrol over comfort.

Also at Cambridge University, Crawford et al. [5] proposed totudy the thermal behavior of the humanitarian shelters in coldlimates in order to deliver elements of design and material spec-fications to allow rapid, high quality and low-cost deployment inmergencies. They compared the different thermal behaviors ofwo prototypes of tents, developed at the Martin Centre, introduc-ng various simplifications: internally the presence of 6 people

as simulated, maximum moisture content was assumed at theime of minimum activity, vapors production of the occupantsas taken from tabulated values by CIBSE (Chartered Institution

f Building Services Engineers), it was assumed a constant evap-ration rate and, above all, a constant external temperature of20 ◦C was considered. Finally, the virtual models were constructedn both samples studied with the use of stationary simulationoftware, ESP-r (Environmental Systems Performance-research),hich were calibrated with data obtained from environmental

hambers tests. Then simulations were carried out using real cli-ate data taken from three different locations but constant over

ime: Islamabad, London and Pristina. The results show that thepportunity to heat a tent with only the solar radiation or onlyith occasional internal gains can only be achieved in just a

ew special climatic conditions; in general shelters were able to

Fig. 1. The tent with the PV stand-alone system.

maintain an internal temperature of 25 ◦C with a constant supplyof 2.4 kW.

More recently Borge-Diez et al. [6,7] made a study on a realinternally displaced camp situated in Haiti after the catastrophicearthquake of 2011. In this case they improved the thermal andenergy behavior of a low cost concrete shelter using also lowcost passive techniques. The study was carried out using varioussoftware tools such as Energy Plus and Design Builder. Dynamicsimulation was considered as a necessary tool to use in develop-ment cooperation. The results showed as, over an entire year, theproposed solutions produced a reduction of 40% in energy demand.The group of Thrall [8,9] worked on a deployable origami-inspiredshelter consisted in deployable rigid walls especially designed formilitary and disaster relief housing. They proceeded to a designoptimization balancing the need of small packaging and easy trans-portation of the shelter and its energy demand. The optimizedsolution was then compared with existing military solutions. Alsoin this case Energy Plus was used to evaluate the thermal energyfrom the HVAC system required to maintain the desired thermalconditions inside the shelter. For the optimized solution the annualenergy demand was 70% less than the standard military tents.

To the authors knowledge only very recently dynamic simula-tion approach has been applied to this kind of environment (tentmade of soft walls). Moreover, very few works can be found inscientific journals with a rigorous study of the problem.

3. Object of the study and on site measurements

The object of this study is a stand-alone photovoltaic emergencyshelter produced by Ferrino in collaboration with Center for Hybridand Organic Solar Energy (CHOSE) and shown in Fig. 1.

The shelter is formed by a steel pole structure, covered only by awaterproof blue fabric made up of 50% cotton and 50% modacrylicfiber, characterized by flame retardant properties; despite thesepositive aspects, this tissue is highly permeable by air and a poorinsulation material.

Above the roof the tent integrates six panels for nautical useconstituted by crystalline laminate silicon, for a comprehensivepower of about 780 Wp. This technology provides an excellent qual-ity/weight ratio (about 17 g/Wp) and a discrete flexibility (about30% of the panel length). The accumulation system is composed by

four batteries for a total of 4.8 kW h of energy capacity, equivalentto 3.6 times the estimated daily energy needs for the tent (it is con-sidered that it should at least provide the charging of 70 phones perday and ensure lighting for 14 consecutive hours).

124 C. Cornaro et al. / Energy and Buildings 88 (2015) 122–134

tent with the sensor location.

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humidity. In fact, if externally it oscillates between 40% and 100%,internally it reaches values close to 100% nearly every day, with analmost constant trend.

Fig. 2. Plan view of the

It is estimated that the installed PV can produce, in extreme sit-ations on the Italian territory, from 300 W h/d (during the winter

n cold climates) to 4 kW h/d (in summer in hot places).The sample of photovoltaic tent studied by the University

f Rome Tor Vergata, was installed in the month of May 2013t the Villa Mondragone in Monte Porzio Catone, near Rome41◦48′50.45′′N–12◦41′32.47′′E), in an unpaved area used for par-ing.

The prototype was oriented with one of the long sides, on whichhe PV panels lie, perpendicular to the south, so as to maximize theolar radiation incidence and with a tilt angle of approximately 20◦.t was also equipped with a system for environmental and energy

onitoring (installed by Tecno-el Srl). This system allows, on oneand, to observe the energy produced in relation to the applied

oads in order to optimize the technological aspects and thus max-mize the useful energy; on the other hand, it allows to acquireata about shelter thermal behavior, which will be used in this dis-ussion to develop a strategy for insulation and air conditioning inrder to improve the internal livability.

The monitoring campaign was conducted from May 7 to May 15013 using the following instruments: a thermo-hygrometer forir temperature and relative humidity both inside and outside theent, an anemometer for wind speed and direction, and finally aight meter for solar radiation measurements. All equipment used

as connected to a data logger CR1000 by Campbell Sci.; this devicellowed data download even from remote, their visualization in realime and their subsequent elaboration through data managementoftware. A plan view of the tent with the location of the sensors ishowed in Fig. 2.

The external air temperature and relative humidity trends dur-ng the test are shown in Fig. 3. The temperature fluctuates from

inimum nocturnal values of around 10 ◦C up to a maximum ofearly 24 ◦C recorded during the hottest hours of the day.

In Fig. 4 it is possible to observe data relative to solar radiationrend during the reference period.

Under these weather conditions the PV system producedpproximately 2.2 kW h/d. This value is aligned with what esti-ated during the design phase.In Fig. 5, the air temperature and the percentage values of rela-

ive humidity measured inside the tent are presented.It can be noted as the temperature inside the tent oscillates

etween minimum values of about 9 ◦C and maximum values that

each even 45 ◦C in the central hours of sunny and clear days, dur-ng which, however, on the outside, it does not reach 24 ◦C. Suchigh temperature values were reached because the tent was keptlosed during the test.

Fig. 3. External air temperature and relative humidity at the monitoring site duringthe period of test.

The temperature difference between inside and outside denotesone of the key issues of these units, within which there areunbearable values of internal temperature. At night, however, thetemperature inside the tent is in line with the external one.

The main problem in the nighttime hours, concerns the relative

Fig. 4. Solar radiation recorded on the plane of the tent roof during the period oftest.

C. Cornaro et al. / Energy and Bui

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ig. 5. Tent internal air temperature and relative humidity during the period of test.

These considerations evidence that the photovoltaic tent doesot have heat and humidity internal conditions such as to ensureffective comfort conditions.

. IDA ICE modeling

A model that reproduced the thermal behavior of the photo-oltaic tent in its present condition was developed. The modelas created with the dynamic building simulation software IDA

ndoor Climate and Energy 4.5. The thermal simulation softwareool is based on a general system simulation platform with a mod-lar approach. The multi-domain physical systems are described inhe IDA through symbolic equations using the Neutral Model For-

at (NMF) simulation language. The simulation tool covers a rangef advanced phenomena such as integrated airflow and thermalodels, CO2 modeling, and vertical temperature gradients [10].To make the model responsive to the real prototype, the geom-

try was defined in detail and also hypotheses were formulatedbout thermo-physical and optical properties of materials consti-uting the tent.

The tent measures 5.85 × 5.02 m and its structure is formed byteel pole. The only coating of poles is constituted by a water-roof blue fabric made up of 50% cotton and 50% modacrylic fiber,haracterized by a density � = 1450 kg/m3 and by excellent flame-etardant properties. Despite its ability to withstand water andre, a fabric, thus composed, has large air permeability (about2.6 m3/h/m2 at a pressure of 50 Pa) and an equally large thermalonductivity �, estimated at 27 W/m K, therefore a poor thermalnsulation. For this tissue a long-wave emissivity was set to 0.77,nd a shortwave reflectance to 0.4, taken as the average value ofeflectance in the entire solar spectrum that characterize the darkreen cotton fabric used by surgeons. This information was usedecause real values for this property were not available.

In the modeling, it was also necessary to consider the presence ofhotovoltaic panels located on the portion of the roof facing south.hese modules absorb a part of solar radiation, that is convertednto heat and transferred by convection toward the inner environ-

ent. It was observed that, especially in the middle of the day, thismount of heat could not be considered negligible compared tohe conditions of internal temperature. For this reason, this heatnput was modeled modulating the solar reflectance of the sin-le part of the roof occupied by the modules. Then setting a veryow reflectance value (equal to 0.001), a considerable increase ofhe internal temperature of the tent was observed that varied as a

unction of the trend of daily solar radiation.

Windows were made of transparent PVC sheets characterized by conductivity � = 0.15 W/m K, a density � = 1450 kg/m3, an emissiv-ty ε = 0.8 and a reflectance r = 0.5. Instead parameters that interact

ldings 88 (2015) 122–134 125

with the solar radiation were varied. In particular, these were sim-ilar to those which characterize a single transparent glass (4 mm).So a solar factor g = 0.92, and a transmission factor t = 0.88 were con-sidered. Moreover, considering that both doors and windows wereprotected by blinds made up of the same fabric of the structure,also the model was equipped with such elements with the samethermo-physical and optical properties adopted for the modelingof the cotton fabric.

As regards the thermo-physical properties that characterizedthe soil in which the tent rested, they were assimilated to those ofa clayey soil with � = 1.5 W/m K, � = 1300 kg/m3 and a specific heatc = 2550 J/kg K.

As considered during the monitoring campaign, the modeledtent was also equipped with three LED lamps (34 W each), turnedon 24 h/24, and a 20 W incandescent lamp turned on from 8 h to20 h.

5. Model calibration

In order to assess improvement solutions, it was necessary tomake sure that the built model, based on the previously madeassumptions, actually corresponded to the observed reality. For thisreason a calibration procedure was implemented using the experi-mental measurements collected during the short term monitoringcampaign. Still a great debate is open in the literature about the pro-cedure to calibrate building simulation models and a recent andextensive literature review can be found in [11]. Both long termand short term calibration procedures are generally adopted andfew works deals with the real differences and benefits betweenthe two approaches [12]. In the present case only short term envi-ronmental measurements were available at a high sampling rate.Calibration was then conducted on a minute base, producing a highaccuracy in the determination of the tent envelope behavior. Indeedthe intent was to precisely tune the tent structure to be able to use itto estimate its energy demand in different periods during the year.

A climatic file (.prn) was built corresponding to the weatherconditions, measured on site. The file listed: the outside air temper-ature, the relative humidity, the direct and diffuse solar radiationand the wind speed. The calibration was carried out comparing thedynamic simulations with the available experimental data for themonitoring period.

As done during the measuring campaign, doors and windowswere assumed constantly closed for the entire simulation period.The tent permeability to air was simulated considering a fixedvalue of air infiltration. Also the condition of infiltration drivenby wind was tested but it did not produce appreciable differenceswith respect to the fixed value for the calibration period. The samefixed infiltration rate was also maintained for the test cases; thiscondition can be considered more conservative for the energy con-sumption calculations at the considered latitudes. However, in thecase of extreme wind conditions this hypothesis could be too strict.The simulation result was quite good but still not perfectly corre-spondent to reality; in fact, as it can be noted in the comparisonchart (Fig. 6), the internal temperature calculated is overestimatedcompared to the experimental data, especially in the warmer hoursof 8th, 9th and May 14th.

To correct the overestimated values, a new simulation was con-ducted considering the doors opened for the period during whichthe temperatures did not match. In effect, in those days, a mainte-nance activity was carried out that led to the opening of both doors.

The data comparison of Fig. 7 shows a better match between thetwo trends of calculated and measured internal temperature, not-ing that the opening of both doors caused a significant temperaturedecrease.

126 C. Cornaro et al. / Energy and Buildings 88 (2015) 122–134

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ig. 6. Comparison between measured and calculated internal temperature, closedoors.

To quantify the accuracy of the calibration, two basic parametersere calculated: the RMSE (root mean square error) and the NRMSE

normalized root mean square error) as shown in the followingquations:

MSE =

√∑ni=1

(Xobs,i − Xmodel,i

)2

n(1)

RMSE = RMSE¯Xobs

(2)

In the case of closed doors a RMSE equal to 3.14 ◦C was obtainednd a NRMSE equal to 14%. Introducing the doors opening in theours of interest a RMSE of 2.7 ◦C was achieved and a NRMSE of2%, both calculated using per minute data relative to the entireimulation period. It was observed that by performing the samealculations with the measured and calculated hourly data, it isossible to obtain a RMSE of 2.3 ◦C, and NRMSE equal to 11%, whichhows that, on an hourly basis, the error is smoothed.

In Fig. 8, the scatter plot related to the two series of dataxpressed on an hourly basis is presented.

A value of R2 of 0.9439 and a trend line angular coefficient equalo 1.0032 was obtained, confirming that the built model can beonsidered calibrated and therefore responsive to the thermal per-ormance of the analyzed solar tent. Moreover it can be noted thathere are some points in the scatter plot that report a more pro-

ounced overestimation of the model with respect to the measuredalues. These data are almost equally distributed in the days of testnd are preferably concentrated in afternoon last hours, in effecthe correspondent measured values exhibit a sudden temperature

ig. 7. Comparison between measured and calculated internal temperature, openedoors.

Fig. 8. Scatter chart of hourly temperatures.

decrease. The cause of this behavior is not clear, maybe it is dueto small variations of air infiltration not correctly simulated by themodel.

6. Results

In order to identify the energy demand of the tent two extremecases for Italy were tested. The city of Turin during the cold sea-son was considered for the evaluation of winter thermal loads (theanalysis was named “cold case”) while the city of Palermo dur-ing the warm season was chosen as reference for the evaluationof summer thermal loads (the analysis was named “warm case”).For both cases the energy demand was calculated for the tent as itis (standard conditions) and for the tent insulated using high per-formance insulating materials to verify the effectiveness of theseimprovements on the energy efficiency of the structure and on theindoor comfort conditions.

6.1. Cold case

In this first analysis a dynamic simulation of the tent was con-ducted for the city of Turin (45◦03′00′′N–7◦40′00′′E) as reference,in a time frame that goes from January 1st to 31st, 2013; Startingfrom the previously calibrated model, the climatic file in the soft-ware database developed by ASHRAE for the city of Turin (Italy)was chosen as climatic reference. In the examined period, outsideair temperature did not exceed 12 ◦C, but often it reached valuesbelow 0 ◦C, with minimum around −6 ◦C. The percentage values ofrelative humidity, however, are highly variable between 10% and100%.

6.1.1. Standard tent with heatingIn this case, the tent was considered with its basic properties,

those on which modeling and calibration were set. Four occupantswere placed (absent at mealtimes) with a winter clothing factor(0.85 ± 0:15 clo) and a metabolic activity level of 1 MET; doors andwindows were kept closed for the entire simulation period but itwas considered an infiltration of 0.6 ACH (Air Changes per Hour), asa typical value for passive house; moreover no shading was consid-ered and the three LED lamps were programmed always off, exceptfor the hours between 4.30 p.m. and 10.30 p.m. The energy require-ments and the power levels useful to warm up the tent with anideal heater were calculated setting a minimum ambient temper-

ature of 17 ◦C and a maximum of 21 ◦C. This temperature rangecan be acceptable in case of emergency situation as recommendedby the United Nations High Commission for Refugees (UNHCR)[1]. However, this range is not sufficient to guarantee comfort

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onditions as prescribed by EN15251 [13] for buildings. For thiseason it could not be possible to appreciate sensible comfort vari-tions with the IDA ICE tool. So, as it is shown in the discussionaragraph, a more detailed analysis was conducted for the tent inassive conditions evaluating the number of hours that falls withinhe range of acceptability, characterized by an operative tempera-ure minimum value of 17 ◦C and a maximum one equal to 25 ◦C.he upper limit of acceptability was fixed in accordance to therovisions established by EN15251.

The graph of Fig. 9 shows the power values during the simu-ation period. It can be noted that the peak power reaches veryigh values, around 6000 W, and minimum values of about 800 W;

t is also important to note that, in the warmest hours, the systemurns off due to the positive contribution of the solar heat gain com-

ined with the internal gains. On the whole an average power of000 W is required with an energy requirement, for the month ofanuary, equal to 2700 kW h corresponding to 92.8 kW h/m2. More-ver, from the heat balance (Fig. 10), it is clear that the heat output

Fig. 9. Power demand of the shelter in standard conditio

Fig. 10. Heat balance of the shelter for the standard conditions wit

ldings 88 (2015) 122–134 127

is comparable to the amount of heat produced by the plant and thatmost of it flows through the walls and the floors, due to the poorinsulating properties of the materials. Moreover the photovoltaictent is a structure that has no thermal inertia, and consequentlytends to establish an equilibrium with the outside temperatureinstantaneously. The indoor air quality result shows that the rel-ative humidity values balance from 14% to 72%.

For what concerns the internal comfort conditions theyobviously correspond to the chosen set temperatures of the heat-ing system; during the central hours of the day thermal comfort isguaranteed mainly because of the incoming solar radiation, how-ever, for the rest of the time the internal temperature is near to theminimum set temperature.

6.1.2. Insulated tent with heatingIt has become apparent that, in presence of cold climates, nearly

all the heat internally produced is lost through walls and floor.For this reason a new case was studied, in the same climatic and

ns during the month of January in the city of Turin.

h heating. “Heat from walls and floor” includes also the roof.

128 C. Cornaro et al. / Energy and Bui

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Fig. 11. Thermal insulating package for walls.

emporal conditions, in which the attempt was to formulate a pos-ible solution to insulate these elements, in order to reduce heatows toward the outside.

For walls and roof insulation (Fig. 11) it was assumed the usef Aerogel incorporated into reinforcing supports (polyester feltedeo-synthetics) which constitute an insulating flexible pad with ahickness of 10 mm, that can be placed inside two layers of cotton.or the floor, instead, it was thought a solution that could addresshe issues for thermal insulation, but at the same time could ensureest conditions of cleaning and livability. A modular floor (Fig. 12)as suggested consisting of polyethylene grids (120 × 60 cm), oftensed to achieve walkable paths or driveways (3 cm) that can be theupport for the inclusion of an extruded polystyrene foam panel3 cm); the whole can be placed on a polyethylene sheet in con-act with the ground and, in order to ensure a surface continuity,nother one could be placed on top.

Parameters related to internal occupants, doors, windows,hading and lighting were the same as the previous study; alsohe simulation period remained unchanged. The tent was heatedith an ideal heater set as for the previous case (Tmin = 17 ◦C,

max = 21 ◦C).The graph on Fig. 13 reveals that, unlike the previous case, the

resence of the insulation counteracts the loss of heat producednside and this means that the power value to ensure the inter-al conditions could be considerably lowered. In this case the peakower demand was lowered to approximately 2500 W and an aver-ge power of 1218 W was required with an energy demand, duringhe month of January, amounted to 906 kW h, corresponding to1.1 kW h/m2. The relative humidity values reached in this case gorom 11% to 75%.

From the heat balance of Fig. 14 it can be seen the contribution

hat insulation of walls and floor gives in order to prevent heat flowsutput.

Fig. 12. Thermal insulating package for floors.

ldings 88 (2015) 122–134

6.2. Warm case

For the study case regarding the “warm case” the city of Palermo,Italy (38◦07′00′′N–13◦22′00′′E) was chosen as the worst case. Theclimatic file was based on ASHRAE’s data (IDA ICE database). Dur-ing the simulation period from August 1st to 31st 2013, the outsidetemperature reached a Tmin = 24 ◦C, a Tmax = 30 ◦C and a mediumRH = 70%. While for the cold case it was necessary to provide a heat-ing system to guarantee inside livable conditions, for the warm casethe standard case and the standard case with insulation were alsotested without a cooling system. Moreover a case in which the com-bination of insulation and a high reflective shading system on thetent was analyzed.

6.2.1. Standard tent without coolingIn this simulation the tent was taken in its standard condition; 4

occupants were placed, this time characterized by a clothing factorequal to 0.3 ± 0.25 clo (summer), the presence of which was pro-grammed as the case related to the cold case. Doors and windowswere assumed constantly opened and the lighting elements activeonly in the evening hours (from 8 to 12 p.m.).

The calculated inside temperature went from 20.5 ◦C to 38.4 ◦Cand relative humidity oscillated from 28% to 90%, but it is importantto note that, compared to the calibration study, in which the modelwas referred to the month of May in a temperate climate with doorsand windows closed, in this case the threshold of 40 ◦C was neverexceeded internally. This shows the great influence that openingshave for losses (or non-accumulation) of heat. This can be well seenin the heat balance shown in Fig. 15.

For the examined case, almost all of the heat produced insidecomes from walls, floor and roof, reaching values of about 10 kW,which is an order of magnitude larger than that produced by theoccupants. This thermal load is the same that is lost primarilythrough the air currents generated by the openings and, for a smallamount, from windows and walls.

Unlike the cold case, for the warm season it was possible toevaluate the thermal comfort with respect to the EN15251 norm toverify the improvement of the internal conditions produced by thetent optimization solutions. The results of this analysis, in termsof the number of hours considered acceptable or unacceptable toguarantee comfort conditions, are described in the discussion para-graph.

For this particular case, considering the tent without cooling,the legislation provides an operating temperature of 32 ◦C as thethreshold of acceptability in terms of thermal comfort. In this case,during the central hours of the day, this limit was exceeded in allcases, while at night, the lower limit of about 24 ◦C was almostalways observed, with the exception of a single day.

6.2.2. Insulated tent without coolingThis second analysis was conducted in order to understand the

possible effects of improvements that could be achieved insulatingwalls and floor. With this aim, the tent was thermally insulatedin accordance with the assumptions previously made for the coldcase. The occupants were always 4 and characterized by the sameparameters as before, as well as the switching times of the lightsand the openings remain unchanged.

In this case the internal temperature is characterized by aminimum of 21.6 ◦C and a maximum of 33.1 ◦C, with a decreaseof nearly 5 ◦C compared to the case where the tent was instandard conditions, thanks exclusively to thermal insulation.

Moreover it was calculated a relative humidity that goes from 30%to 88%. It is possible to observe, Fig. 16, that in this case, the thermalload entering through the envelope reached only 1500 W (com-pared to 10,000 W in standard conditions) due to the presence

C. Cornaro et al. / Energy and Buildings 88 (2015) 122–134 129

ent w

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Fig. 13. Power demand of the shelter for the case “insulated t

f insulation. Moreover, now the number of hours that ensuredhermal comfort was sensibly increased.

.2.3. Insulated tent with coolingIn this third analysis an ideal cooler was set to guarantee better

hermal condition inside the tent in summer. The tent was con-idered with insulation, considering the ameliorative effects that itmplied; the internal gains parameters were maintained as the pre-ious cases for the warm case with the exception of windows andoors that were set constantly closed to minimize the heat inputrom outside with the exception of the infiltration value of 0.6 AHC.

The cooler was set to maintain an internal temperature of 26 ◦C.hese conditions could be maintained with an average power ofbout 880 W and with an energy demand for the entire month of

ugust equal to 653 kW h (Fig. 17), corresponding to 22.4 kW h/m2.he requested peak power reaches approximately 2200 W. Further-ore it was calculated a minimum value of relative humidity of

bout 50% and a maximum one equal to 88%.

Fig. 14. Heat balance of the shelter for the case insulated tent with

ith heating” during the month of January in the city of Turin.

In this case, the thermal load input is made by the heat producedby the occupants, but in predominant amount, by the heat enter-ing through the envelope; it is important to note that this valueis less than approximately 8500 W with respect to the amount ofheat that passes through the same elements in standard conditions(Fig. 18). The same graph shows how almost all of the heat pro-duced internally is removed from the inside thanks to the coolingsystem.

However, in terms of thermal comfort no improvement wasobserved. EN15251 considers comfort conditions for a maximumoperative temperature of 27 ◦C in the presence of a cooling systemwhile in the case of no cooling this limit is shifted to more than30 ◦C. In this case, even if the air temperature can be maintainedat the comfort value of 26 ◦C the same thing could not be obtained

for the operative temperature that remains quite high, reaching amaximum of approximately 30 ◦C. This is mainly due to the ele-vated temperature reached by the tent surfaces which contributeto increase the operative temperature values.

heating. “Heat from walls and floor” includes also the roof.

130 C. Cornaro et al. / Energy and Buildings 88 (2015) 122–134

hout c

6

cIpTt

Fig. 15. Heat balance for the case “standard conditions wit

.2.4. Insulated tent with shadingIn this last analysis the study of an alternative solution to

ooling, to improve inner environment conditions, was proposed.

n particular a shading element was modeled, consisting of aolyethylene sheet, for which the reflectance was set equal to 0.98.his parameter describes the behavior of a fully reflective surfacehat does not allow the solar radiation to enter into the shelter.

Fig. 16. Heat balance for the case “insulated tent without coo

ooling”. “Heat from walls and floor” includes also the roof.

Furthermore, in order to reduce the amount of direct solar radia-tion on the inclined walls, a horizontal shading was modeled whoseprojection on the ground is slightly higher than the flat surface of

the tent. For this object, however, the software did not allow to setany optical parameters, so this surface was not considered reflec-tive. A sketch of the considered shelter is shown in Fig. 19. Wallsand floors were considered insulated; doors and windows were set

ling”. “Heat from walls and floor” includes also the roof.

C. Cornaro et al. / Energy and Buildings 88 (2015) 122–134 131

nt wi

co

diiR

otdiofoc

Fig. 17. Power demand of the shelter for the case “insulated te

onstantly opened and the parameters regarding internal gains andccupants were maintained as previous hot climates cases.

The inside temperature registered with this simulationecreased of about 2 ◦C than the case in which the shelter was

nsulated without shading; but this value decreased of about 7 ◦Cf compared to the results of the simulation in standard conditions.elative humidity went from 30% to 91%.

From the heat balance in Fig. 20, it can be seen that the amountf heat entering through walls, floors and solar radiation reachedhe peak of 1000 W but in the middle of the day, when the inci-ent solar radiation reached its maximum, it dropped to a level of

ncoming heat of just 600 W. This value reached 2000 W, in the case

f the tent insulated but not shaded by the reflective sheet. This dif-erence between the two cases exists because, in the central hoursf the day, when the solar incident radiation is near to the verti-al, the shading reflects a very big part of it proportionally to its

Fig. 18. Heat balance of the shelter for the case insulated tent with

th cooling” during the month of August in the city of Palermo.

tilt. In the other hours of the day the sun is lower in the sky andthe solar radiation reaches the east and the west surfaces that arenot covered by the reflective shading, so the amount of heat inputis higher. In the case without shading, instead, the solar radiationwas absorbed in relation to the reflectance parameter of the canvas.

7. Discussion

The results obtained for the Cold case are summarized in Table 1.In the table also the two cases without ideal heating are shown.

It can be noted that under standard conditions, the internalair temperature reaches minimum values even below zero, cer-

tainly not acceptable in terms of comfort. By placing a layer ofinsulation based on aerogel on the inner walls and roof of thetent and using a modular insulated floor composed by extrudedpolystyrene monolayer foam (insensitive to the rise of water

cooling. “Heat from walls and floor” includes also the roof.

132 C. Cornaro et al. / Energy and Buildings 88 (2015) 122–134

Table 1Cold case results.

Turin Tmin (◦C) Tmax (◦C) Pmax (W) Pavg (W) Energy (kW h) Specific Energy (kW h/m2)

Standard −3.8 27 – – –Insulation −1 29 –

Standard + heating 17 26.5 6577

Insulation + heating 16.8 29.1 2445

apismtmpa

Fig. 19. Shading system considered for the modeled shelter.

nd suitable to be placed in direct contact with the ground), it’sossible to raise the minimum temperature of 2.8 ◦C. The remain-

ng two cases are used to evaluate the energy demand of thehelter, in order to significantly improve the internal environ-ental conditions. The insulation solution proposed could lower

he required average heating power from 3600 W to approxi-ately 1200 W with an energy demand for the month of test that

asses from approximately 2700 kW h to almost 900 kW h with 67% reduction in energy consumption. The requested power

Fig. 20. Heat balance of the shelter for the insulated tent with s

– –3629 2700 92.81218 906 31.1

and energy in the absence of insulation solutions, in additionto represent a large economic burden, are not always avail-able in emergency situations. If instead the tent is insulated theenergy request appears much more accessible. However, it isnecessary to clarify that these considerations can be made onthe basis of a system in which the doors are never opened. Itwas observed that instead, in the case of short openings (about10 min for three times a day), the power required to maintainthe above described conditions can reach the peaks of almost7 kW.

The maximum temperatures reached inside the tent alsodeserve some comments. It can be noted as in the tent with insula-tion the inner air temperature reached 29 ◦C, which is quite far fromthermal comfort conditions. This temperature increase is mainlydue to the solar radiation that, especially in the clear sky days,warms the tent that cannot dissipate the excess heat effectivelydue to the insulation layer. However, as already stated, these resultshave been obtained with doors never opened while in this situationdoors opening can be used to mitigate the inside air temperature.

Even though for the cold case it was not possible to appreci-ate environmental improvement with the IDA ICE tool based onthe EN15251 for buildings, a thermal comfort analysis was con-ducted fixing a range of acceptability between 17 ◦C and 25 ◦C, asprescribed by legislation in emergency situation [1]. The results

obtained considering the tent in passive conditions are shown inFig. 21.

The study reveals that the use of insulation can provide toincrease the number of hours of acceptability reducing those of cold

hading. “Heat from walls and floor” includes also the roof.

C. Cornaro et al. / Energy and Buildings 88 (2015) 122–134 133

Table 2Warm case results.

Palermo Tmin (◦C) Tmax (◦C) Pmax (W) Pavg (W) Energy (kW h) Specific Energy (kW h/m2)

Standard 20.5 38.4 – – –Insulation 21.6 33.1 –

Insulation + cooling 24 26.1 2186

Insulation + shading 21.5 31.2 –

Fe

drccpttc

tsoi5irtiai

Fe

ig. 21. Comparison of acceptable and unacceptable hours of comfort for the differ-nt solutions for the cold case.

iscomfort but, at the same time, induces the increase of those thatepresent heat discomfort. On the whole a very small improvementan be observed for this situation. The insulated with heating casean obviously guarantee comfort conditions in the considered tem-erature range so it has been omitted in the graph. However, it haso be pointed out that in winter conditions heating is necessary sohe use of insulation solution is more effective to reduce energyonsumption than to improve comfort conditions.

Table 2 shows the results referred to the warm case. It is seenhat, under standard conditions, the Tmax reaches 38.4 ◦C, repre-enting the main problem to be faced. Instead, using the same typef insulation for walls, floor and roof as used in the cold case, its possible to bring down the maximum temperature even about.5 ◦C, significantly improving the thermal comfort. Even if the cool-

ng power requested for the tent conditioning can be consideredeasonable, however, it is evident that this solution does not bringo comfort conditions, as prescribed by EN15251 in the case of cool-

ng. It can also be noted that, using only passive cooling systemss a reflective polyethylene shade cloth combined with a suitablensulation of walls and floor, it is possible to obtain approximately

ig. 22. Comparison of acceptable and unacceptable hours of comfort for the differ-nt solutions for the warm case.

– –880 653 22.4

– –

good internal comfort conditions considering the limit of the normwithout cooling systems.

Fig. 22 shows the results obtained in terms of comfort con-ditions for the various warm cases without cooling. The resultsare represented as acceptable and unacceptable hours of thermalcomfort (heat and cold discomfort). The solutions of insulationwith shading offers the best conditions, confirming that the useof passive conditioning systems produces high acceptable level ofcomfort, compatible with the temperature range limits imposedby EN15251 in the case of no cooling systems installed. In this casethe hours when the environmental conditions are defined unac-ceptable are only 4, about 3.2 % of those relative to the case wherethe tent was only insulated (122 h), with a consequent increase inthe hours defined very good, good or acceptable.

8. Conclusions

A rigorous study on the thermal behavior of a shelter used inemergency situations was carried out for the Italy climatic condi-tions. A building dynamic simulation software (IDA ICE 4.5) wasused for this scope after that an accurate calibration procedurewas performed using on site measurements. Two extreme climaticcases for Italy were tested using ASRHAE climatic data of the cityof Turin for winter conditions (cold case) and of the city of Palermofor summer conditions (warm case). The study allowed to inves-tigate the thermal behavior and the thermal comfort conditionsinside the shelter in its standard configuration (i.e. without anythermal improvement on the structure) and after high insulat-ing material (aerogel pad) and a particular treatment of the floorwere introduced in the original design. It has to be remarked thatthe proposed solutions are easy to implement and contributes tolower the energy demand of the tent to half of what requested instandard conditions during the more critical winter period. In thecold case these solutions also contribute to slightly improve theinternal comfort conditions considering an acceptable temperaturerange between 17 ◦C and 25 ◦C; nevertheless it wasn’t possible torefer the results obtained to the legislation in force for buildings(EN15251) because the internal conditions of the tent were lowerthan the standards expected for buildings. During the summer theimprovement due to thermal insulation allows to lower the insidetemperature of almost 6 ◦C without mechanical cooling; even if theuse of a cooling system can sensibly reduce the inside air tempera-ture, it is not able to mitigate the operative temperature that stayshigh and not compatible with the operative temperature rangeprescribed by EN15251 in the case of cooling. Passive condition-ing solutions can guarantee comfort conditions that are acceptablewhen no cooling system is provided. The presented approach couldbe used to test also other optimization solutions and test them forvarious types of climates.

Acknowledgments

The authors wish to thank Ferrino company for providing andinstalling the Montana tent. CHOSE is funded by the Lazio Regionand the project was also funded by the Lazio Region.

1 nd Bui

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1992, ‘Thermal Performance of the Exterior Envelopes of Buildings’, Clearwater

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