investigation on the thermal performance of green facade in ......international journal of...

International Journal of Architecture, Engineering and ConstructionVol 7, No 1, March 2018, 26-33

Investigation on the Thermal Performance of Green Facade in

Tropical Climate Based on the Modelling Experiment

Ratih Widiastuti1,∗, Eddy Prianto2 and Wahyu Setia Budi3

1Department of Architectural Design, Vocational School, Universitas Diponegoro, Semarang, Indonesia

2Department of Architecture, Faculty of Engineering, Universitas Diponegoro, Semarang, Indonesia

3Department of Physics, Faculty of Mathematics and Sciences, Universitas Diponegoro, Semarang, Indonesia

Abstract: This study presents an in situ experimental study of buildings covered by green facades in the tropical countryof Indonesia. A scaled model called house miniature was used as measurement object. The aim of this study is to examinethe influence of green facades on the thermal performance of buildings. Data measurement is recorded during rainy seasonwhere the average of humidity is 69.35% and the average of ambience temperature is 24.48◦C. Considering overall thermalperformance, model with green facade has lower surface temperature and indoor air temperature than model without greenfacade. On the surface temperature, the differences with model without green facade are 6◦C for exterior facade and 6.3◦Cfor interior facade. Compared to model without green facade, in the morning, indoor air temperature of model with greenfacade tends to increase up to 25.6◦C. Meanwhile, in the afternoon until evening, indoor air temperature tends to decreaseup to 25.6◦C. Thus, it is beneficial to create indoor thermal comfort. However, green facade will produce higher humidity inthe model and becomes a disadvantage. Based on the data measurement, indoor air humidity of model with green facade is42.93% higher than model without green facade. This condition can be a reason of discomfort for building occupants.

Keywords: Green facade, modelling experiment, building thermal performance

DOI: http://dx.doi.org/10.7492/IJAEC.2018.004

1 INTRODUCTION

One of the negative effects of city development is the decreaseof greenery area (Wong et al. 2010; Chen et al. 2013).Human tend to use each part of the city as building areaand cause higher temperature of surrounding ambient. Dueto limited area, conventional parks are difficult to realize inthe cities. The present of vertical greenery system then be-come one of solutions to encounter this problem (Francis andLorimer 2011). Even though trend of using vertical greenerysystem can not play as water catchment, as building envelopeit become more common.

Some of major cities in Indonesia, such as Jakarta, Surabaya,Bandung and Semarang hav been using vertical greenery sys-tem as one of building’s element. However, based on the obser-vation, it seems just to increase building aesthetic rather thanbuild thermal performance and lack of maintenance causessome of plants to die and ruins facade appereance.

In the building science research, vertical greenery system notonly as building aesthetic but also as part of passive coolingdesign beneficial to increase energy saving. In the dense urbanareas where the walls of high rise building are the largest part

of the building that has potential benefits for green facadeas building envelope (Cheng et al. 2010; Jim and He 2011).Probably, an even greater potential is for low and medium res-idential, industrial and commercial buildings to create greenfacade.Plant in the building envelope will reduce solar radiation

and produce humidity through evapotranspiration (Scudo andOchoa De La Torre 2003). These effects are beneficial especial-ly during summer months when plant shading can reduce heatflow and decrease temperature on the building surface (Wonget al. 2010).Another study conducted by Peck et al. (1999), said that

walls and windows shaded by vertical greenery system can re-duce the amount of energy needed for air-conditioning by 50%to 70%. Result of study conducted by Bass and Baskaran(2003), also said that the shading effect of vertical greenerysystems can reduces 8% annual energy consumption. It meanswhen all building facades covered by vertical garden, potentialfor energy saving also improve (Dunnett and Kingsbury 2004;Alexandri and Jones 2008; Köhler 2008).A number of studies in vertical greenery systems were pub-

lished. First, using eights types of vertical greenery system,

*Corresponding author. Email: [email protected]

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http://dx.doi.org/10.7492/IJAEC.2018.004

mailto:[email protected]

Widiastuti et al./International Journal of Architecture, Engineering and Construction 7 (2018) 26-33

a study conducted by Wong et al. (2010) said that verticalgreenery system potentially can reduce surface temperatureon the building facade and ambient temperature in the trop-ical climate. Another result from this study is the effect oftemperature reduction depend on the various types of verticalgreenery system. However, this research did not answered theeffect of vertical greenery system in the indoor.Second, Mazzali et al. (2013), has been extended a study

of three living wall field tests to heat flux calculated on thebuilding facade. This study conducted in the Mediterraneantemperate climate in the different location. Even thought theliving wall applied in the outside of building facade, but thereis no calculation in the indoor temperature. Furthermore,there is difference in building materials. It would be better ifthe study used one kind of building material.Third, a study conducted by Widiastuti et al. (2016), ex-

plained that facade with vertical garden has longer thermallag than bare facade. This result has explained that verticalgarden beneficial to reduce cooling load during peak hours.However, the short period of data measurement did not an-swered the behaviour of vertical garden in the night. More-over, the position of bare facade and vertical garden are indifferent elevation, possibility influenced in thermal condition,both outdoor and indoor.Based on the literatures review, remain of studies in vertical

greenery system are enigmatic. It means, possibility to devel-op this research is promising, especially in tropical countrieslike Indonesia.This study observe the effects of green facade on the building

thermal performance. The observation includes profile of in-door air temperature and indoor air humidity. Different withprevious studies, the experiments use scaled model with thematerials and the condition same as a real building. Datameasurement was done for 24 hours to find out the buildingthermal profile on the night.

2 METHODOLOGY

2.1 Description of Study Object

In this study, an experiment in situ was conducted to create asituation that was same as real building using vertical green-ery system. Study object is a model like house called houseminiature. It illustrates a single story building, as seen inFigure 1.

Figure 1. House miniature as study object

Details of the building materials on the model explains inTable 1. While, the comparison scale between model and realbuilding is 1:4, seen in Figure 2.

Table 1. Details of model

No Details of model Specification1 Model size 1m x 1m x 1m2 Roof material Asbestos3 Roof shape Gable roof4 Wall material Brick5 Inlet outlet Porosity 30 %6 Floor material White ceramic7 Ceiling material Asbestos8 Position Inlet in the front and

of opening outlet in the back

Figure 2. Detail of house miniature

On the December 2013, the study began to collect datafor model without vertical greenery system. After that, onthe same week, the data measurement for model with verticalgreenery system was conducted.

2.2 Description of Vertical Greenery System

There are two kinds of green facade:

2.2.1 Direct Green FacadeAs seen in Figure 3, direct green facades is climber plantsthat self-clinging on the building exterior using its roots. Thistechnique also can using wire or cable as supporting material.Even though building that covered by green facade can reducewall temperature, but self-climber plant may damage buildingconstruction especially on the wall surfaces (Sternberg et al.2011; Perini et al. 2013). Planting climber plants in the soilat the base of a wall is cheap and highly effective for greeneryfacade (Dunnett and Kingsbury 2004; Hopkins and Goodwin2011).

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(a)

(b)

Figure 3. Illustration of direct green facade. (a). Self cling-ing of green facade; (b). Simply supporting struc-ture of green facade (modified from Widiastuti etal. (2016))

2.2.2 Green Facade with Double-Skin System

Double skin system in green facade rely on the supportingmaterial such as modular trellises, stainless steel cable, orstainless steel/HDPE mesh to assist the upward growth ofa wider variety of climbing plants. This technique will createsmall cavity between green facade and building wall, as seenin Figure 4, different from direct green facade that attachedin the building wall. In addition, double-skin green facadescreate an insulating layer of air between the foliage and build-ing wall (Köhler 2008; Ottelé et al. 2011; Perez et al. 2011a;Perez et al. 2011b).Based on the theory, in this study we used direct green fa-

cade as vertical greenery system (Sternberg et al. 2011; Periniet al. 2013). Climber plant attached directly in the facadeused mesh trellis, while the plant roots was planted in theplanter boxes. The facade covered by green facade orientatedto face the east according to sunlight direction. In the follow-ing are detail of green facade:

1. Step one, plants choice. Passiflora flavicarva and Pseu-docalymma alliaceum are kinds of climbing plan usedas green facade, as seen in Figure 5. Mesh trellis usedto support the plants in order can be climbed on thefacade.

Figure 4. Illustration of direct green facade. Green facadewith double-skin system (modified from Hunteret al. (2014))

Figure 5. Climbing plants for green facade application. (a).Pseudocalymma alliaceum; (b). Passiflora flavi-carva

2. Step two, planting the climbing plants. The roots ofclimbing plans were planted in the boxes filled with soilto simulate the ground. The plan grew quickly duringthe first months, as seen in Figure 6. Once the planthigh reached 2-3 m, it would be moved on the houseminiature as green facade.

3. Step three, green facade installation. The green facadewas installed in December 2013. Using mesh trellis thatentwined to support plant to climb on the wall. Themesh trallis attached on the ones of building facades forplant to climb. The leaves and stems furled around thetrellis mesh, covered facade, filled the area and provid-ed dense foliage for the green facade. The facade areacovered by green facade is 1 m2, as seen in Figure 7.

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Figure 6. Planting process of climbing plant

Figure 7. Process of attaching climbing plant on the houseminiature facade

2.3 Experiment Description

The experiment was conducted in Architecture Department,Universitas Diponegoro, Semarang City (6◦58’0.0012”S and

110◦24’59.9904”E), as seen in Figure 8. The site is an openarea surrounded by trees and buildings. Condition at that mo-ment, the trees have been cut and the sunlight is not blockedby trees.

Figure 8. Location of experiment, Semarang City, Indone-sia

The measurements was conducted to validate the thermalprofile of the model and consisted of three data measurements.Both for model with and without green facade, can be seen inFigure 9. In the following are detail of data measurement:

1. Measurement of surface temperature on the interior andexterior facade.

2. Measurement of air temperature in the exterior and in-terior of house miniature.

3. Measurement of air humidity in the exterior and interiorof house miniature.

There are nine measured points on the facade surface, threeon the bottom, three on the middle and three on the top. Thedata of surface temperature are the average from the nine mea-sured points. Whereas for indoor air temperature and indoorair humidity, the measurement tools placed in the middle ofhouse miniature.This research used some of measuring instruments :

1. Hygrothermometer used to measure air temperatureand air humidity in exterior and interior of house minia-ture.

2. Infrared surface thermometer used to measure surfacetemperature, both exterior and interior of facade.

3. 4 in 1 environment tester LM-8000 used to measure windspeed.

2.4 Local Climate Condition

Data collecting was done in three days in December 2013.Beginning on 16th December 2013 at 6:00 am until 19th De-cember 2013 at 5:00 am. These three days were cloudy andsunny. There is no solar radiation measurement. However, weused solar illuminances as indication as solar radition.Generally, during data measurement of model with green

facade, the weather is hot and humid, and the average of hu-midity is 69.35%, varying from 64.00% to 76.00%. The aver-age of ambience temperature is 24.48oC, varying from 23.00oC

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Figure 9. (A). Exterior side of field measurement with green facade; (B). Data collected of model without green facade;(C). Data collected of model with green facade

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Intensity of solar illuminances *10 lux Wind speed Temperature Humidity

Figure 10. Profile of local climate condition during data measurement

Table 2. The weather conditions during the experiment

No. Values of Outdoor air Relative Wind Intensity of solarweather condition temperature (◦C) humidity (%) speed (m/s) illuminances (*10 lux)

1 Highest values 26 78 1 155.62 Average values 24.48 69.35 0.26 45.653 Lowest values 23 64 0 0

to 26.00oC, as seen in Table 2 and Figure 10. The minimumtemperatures are recorded during afternoon until night at 6:00pm-1:00 am. The highest maximum temperatures are record-ed during morning at 08:00 pm-11:00 pm.Extreme thermal condition frequently recorded when heavy

rain happened, especially in the day time. To achieve theaccurate results, data were collected every an hour. Datameasurement was only used in the sunny condition. It wasindicated by higher illuminances that means higher incidentsolar radiation.In order to carry out a more detailed study on the climatic

conditions during the data measurement. The data of localclimate condition were grouped by four categories: morning,day time, afternoon and night.

2.4.1 Day Time-AfternoonDuring the day time, intensities of solar illuminances de-creased 14.32% between 12:00 pm-4:00 pm, caused by cloudy.However, between 1:00 pm-4.00 pm, the average of humidityincreased 2.51% and the average of air temperature decreased

0.79%, from 26.00◦C to 25.00◦C. At that moment, the averageof air movement was 0.5m/s. The highest solar illuminancesrecorded at 12:00 am and became the lowest humidity duringthe day time. While the highest of humidity was 76% recordedat 5:00 pm–6:00 am.

2.4.2 NightDuring the night, air temperature decreased from 24.00◦C to23.00◦C, because of air movement and the decreased of so-lar radiation. The humidity also decreased from 72.00% to64.00% recorded around 6:00 pm-2:00 am. However, around3:00 am to 5:00 am, the humidity increased up to 68.00%.

3 RESULTS AND DISCUSSION

Because the weather was in sunny and cloudy condition, datafrom rainy and full cloudy days were excluded and only usedthe averages data from full sunny days. The average of ther-mal profile for 24 hours period for the model without greenfacade and with green facade are compared.

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Exterior surface temperature of model without green facade Interior surface temperature of model without green facade

Eksterior surface temperature of model with green facade Interior surface temperature of model with green facade


3.1 Comparison between Surface Tempera-tures

As shown in Figure 11, it is noticeable that surface tempera-ture in the model without green facade is considerably higherthan surface temperature in the model with green facade. Ingeneral, the average of surface temperature difference betweenmodel without and with green facade are 6.00◦C for exteriorfacade and 6.30◦C for interior facade. A reduction in surfacetemperature will reduce thermal stress on the building mate-rials, especially in the regions with higher solar radiation.

Nevertheless, during the night with lower solar radiations,both exterior surfaces temperature recorded were cooler thaninterior surface. It was from heat accumulation during theday, made interior surface temperature was higher than exte-rior surface temperature. The effect of this condition is interiortemperature will warmer than ambient temperature.

The first balanced condition between exterior and interiorsurface temperature of model without green facade occurredat 6:15 am (28.35◦C) and the second balanced condition oc-cured at 6.30 pm (31.60◦C). However, in the model with greenfacade, the first balanced condition between exterior and in-terior surface temperature occurred at 5:30 am (22.43◦C) andthe second balanced condition occurred in the evening at 4:30pm (24.10◦C). Through the result, model with green facadetend to faster in the cooling its surface temperature.

Further effect of this condition is peak of surface tempera-ture on the model without green facade occurred faster, forexterior facade around 1:00pm, (35.40◦C) and for interior fa-cade around 6:00 pm (31.80◦C). Meanwhile, on the modelwith green facade, peak of exterior surface temperature oc-curred around 11:00 am (33.40◦C) and for interior surfacetemperature occurred around 6:00 pm (25.40◦C). The posi-tion of peak temperatures will lead how long thermal lag onthe model and how much cooling load can be reduced duringpeak hours. Based on the calculation, model with green fa-cade has thermal lag 2 hours longer than model without greenfacade. It means green facade will reduce the amount of heatthat received by facade.

3.2 Comparison between Indoor Air Temper-ature

Generally, indoor air temperature on the model with greenfacade was lower than model without green facade, as shownin Figure 12. Decrease on the surface temperature caused de-crease in indoor air temperature. The mean difference reachesup to 1.27◦C.Based on the data measurement, at the morning indoor air

temperature tend to increase up to 25.60◦C (10:00 am). Mean-while, at the afternoon until evening, after static period, in-door air temperature tend to decrease up to 25.60◦C (6:00pm)and decrease more in night time. This condition is differentfrom model without green facade that tend to static until nighttime, at the range 26.50◦C.Possibility, it was from evapotranspiration that made the

process of heat release on the model occurred more rapidlyand reduce the amount of energy from solar radiation (Scudoand Ochoa De La Torre 2003; Mazzali et al. 2013). In themeantime, at night until morning green facade tend to isolat-ed heat from facade. Thus, the room will be warmer. Thiseffect is beneficial to create indoor thermal comfort.The highest difference between indoor air temperature of

both model recorded during the night, approximately 0.80◦Cto 1.70◦C. The peak of indoor air temperature on the modelwithout green facade occurred at 26.60◦C for 9 hours, whichwas 5 hour longer and 26.00◦C higher than model with greenfacade. It means in these hours, the model without green fa-cade need more energy to cooling down the indoor air temper-ature. As a shadowing element, green facade can manage toreduce indoor air temperature, by preventing the overheatingof exterior surface temperature.

3.3 Comparison between Indoor Air Humid-ity

Generally, as shown in Figure 13, model with green facade hashigher indoor air humidity. Actually, during the data measure-ment, the indoor air humidity of model with green facade tendto be static and in several times, its record has 100% humidity.The average of its indoor air humidity is 98.33% and higher

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Air

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Indoor air humidity of model without green facade Indoor air humidity of model with green facade


42.93% than model without green facade.According to Scudo and Ochoa De La Torre (2003), this

is due to evapotranspiration. Plant will prevent air contain-ing water vapor moving. The result is high humidity in theroom. In addition, possibility of high humidity can be causedby weather conditions and size of model. Data measurementdone in the rainy season, when the ambience humidity washigh and the size of model is small, giving possibility to pro-duce high humidity in the room.Even though air temperature on the model with green fa-

cade was cooler than model without green facade, never-theless if indoor air humidity beyond of standard (30.00%-60.00%) (Balaras and et al. 2007; Wolkoff and Kjaergaard2007), this condition can be a reason of discomfort for build-ing occupant, especially for 24 hours daily use. Hence, forspecial building such as housing, applying green facade in thebuilding must be taken into account.

4 CONCLUSION

This is a series of studies which aims to prove the influencesof vertical greenery system regarding thermal conditions in

the building. In this work, a model with green facade wereconducted and the aim was to extend the result of previousworks.Based on data measurement, model with green facade has

lower surface temperature and indoor air temperature thanmodel without green facade. The mean differences of surfacetemperature between model without and with green facade are6◦C for exterior facade and 6.30◦C for interior facade. How-ever, in the night, both exterior surface temperature recordedcooler than interior surface. It was from heat accumulationduring day time, made interior surface temperature was high-er than exterior surface.Possibility of green facade application to create indoor ther-

mal comfort can be seen from the data measurement. In themorning, indoor air temperature of model with green facadetend to increase up to 25.60◦C. Meanwhile, in the afternoonuntil evening, after static period, indoor air temperature tendto decrease up to 25.60◦C. This condition is different frommodel without green facade that tend to static until nighttime, at the range 26.50◦C.Higher humidity in the model with green facade becomes

a disadvantage of green facade application. Even though

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air temperature on the model with green facade was coolerthan model without green facade, if air humidity higher than70.00%, this condition can be a reason of discomfort for build-ing occupant.

ACKNOWLEDGEMENT

This research is fully supported by LPDP scholarship. Theauthors fully acknowledge Indonesian Ministry of Finance forthe approved fund which makes this important research viableand effective.

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