International Journal of Architecture, Engineering and ConstructionVol 5, No 1, March 2016, 13-20

Performance Evaluation of Vertical Gardens

Ratih Widiastuti1,∗, Eddy Prianto2 and Wahyu Setia Budi3

1,2Architecture Department, Faculty of Engineering, Diponegoro University

Tembalang-Semarang, 50275, Indonesia

3Physics Department, Faculty of Mathematics and Sciences, Diponegoro UniversityTembalang-Semarang, 50275, Indonesia

Abstract: This paper presents a study about vertical garden as one of the most popular greenery systems in themodern era. The aims of this research are to study the thermal performance of the vertical garden in the officebuilding and the influence of weather parameter toward the thermal performance of vertical garden. The objectstudy was the application of vertical garden in Pertamina branch office building, Semarang, Indonesia. Thevertical garden model has been verified with a set of measurement tools that measured weather parameter andthermal performance for both bare and vegetated façades. The measurement demonstrated that the plant layeron the façades can effectively reduce the interior surface temperature on the façades. The average difference was2.1C. When the outdoor air temperature increased, surface temperature of vegetated façades also increased.The effective thermal resistance of a plant layer gradually decreases when the air temperature rises. It can beconcluded that the performance of vertical garden is influenced by the weather around the building.

Keywords: Interior surface temperature, thermal reduction, weather condition, vertical garden

DOI: 10.7492/IJAEC.2016.002

1 INTRODUCTION

Recently, greenery aspect has spread widely as an ar-chitectural element to design building façades and ro-ofs. It becomes more popular along with rapid mod-ernization that changed the existing ecosystems andreplacing with hard materials such as asphalt, pavingand concrete which resulted temperature increase inevery day. Though not a new concept, greenery as-pects in the building has increased the percentage ofgreenery in urban built-up area and bring back thevanishing urban green space (Wong et al. 2003).One of the most popular greenery systems is vertical

garden. On the market, many kinds of vertical gard-ens are available and it is possible to distinguish themaccording to their constructive technology and to thetype of green cover which can be grass or plants. Thepossibility of reducing heat transfer through the build-ing envelope became a plus point of vertical garden(Holm 1989).In Indonesia, research related to greenery aspects on

the building as a passive cooling system for energy sav-ing was so rare. Mostly the research discussed ther-

mal comfort based on the trees quantity in the outdoorspace such as streets, pedestrian or parks.This research studies about the thermal performance

of the vertical garden in the office building and the in-fluence of weather parameter toward the thermal per-formance of vertical garden.

2 LITERATURE REVIEW

2.1 What is Vertical Garden

Green wall or vertical garden is the term used to re-fer to all forms of vegetated wall surfaces (Sharp et al.2008). Vertical garden is not only for building aesthet-ic, but also provides a sustainable, energy saving, com-fortable and healthy environment for building occupant(Rashid et al. 2010). It is rooted into the ground, onthe wall or in modular panels attached to the façades.It is also called a system to attach plants to civil en-gineering structures and walls of buildings or verticalgreened façades are walls that are either partially orcompletely covered with vegetation, and they have ex-uberant green looks (Yeh 2010).

*Corresponding author. Email: shine_frontier@yahoo.com

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Some plants are able to grow on walls by taking rootin the substance of the wall itself. Typical of theseare mosses, lichens, grasses and vines. For these togrow successfully on walls and buildings, some kindsof support structure is usually essential (Johnston andNewton 2004).

According to growing method, vertical garden canbe classified as green façades and living wall system(Dunnett and Kingsbury 2004; Köhler 2008). Greenfaçades are made up of climbing plants either growingdirectly on a wall or in specially designed supportingstructures. The system of plant shoot grows up theside of the building while being rooted to the ground.Green façades use climbing plant attached directly tothe building surface or supported by cables or trellis,as seen in Figure 1.

Figure 1. Illustration of green façade

On the other hand, living wall systems are construct-ed from modular panels which contain soil or otherartificial growing mediums, for example planter box,foam, felt, geotextile, perlite and mineral wool, as seenin Figure 2, the panels require hydroponic cultures us-ing balanced nutrient solutions to provide all or part ofthe plant’s food and water requirements (Sharp 2007;Dunnett and Kingsbury 2004). This system usuallyemploys evergreen plants as small shrubs which do notnaturally grow vertically.

Figure 2. Living wall system illustration: (a)planterbox system, (b)foam system, (c)mineralwool system

2.2 Thermal Benefits-Temperature Reduc-tion

Plants, especially vertical greening systems can pro-tect the building envelope against the sunshine andfreezing weather, which is beneficial for the thermalbehaviour of the building indoor as well as outdoor.Vertical greening systems improve thermal insulationcapacity through external temperature regulation. Theextent of the savings depends on various factors suchas climate, distance from the sides of buildings, build-ing envelope type and density of plant coverage (Wonget al. 2010; Akbari et al. 1997). Therefore, apply-ing vertical garden can influence both the cooling andheating (Akbari et al. 1997).Vegetation can play an important role in the topo-

climate of towns and the micro-climate of build-ings (Wong et al. 2010). Despite that, vegeta-tion can dramatically reduce the maximum temper-atures of a building by shading walls from the sun,with daily temperature fluctuation being reduced byas much as 50% (Dunnett and Kingsbury 2004).The shading and the corresponding reduction of thetemperature, are the reason that climbers common-ly used in Mediterranean areas against walls or asa canopy over terraces (Hermy et al., 2005). Plantcanopies that shade buildings move the active heatfrom the building envelope to leave (McPherson et al.1988).

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Another statement by (Akbari et al. 1997), said thatcooling energy potential of shade trees by reductionof the local ambient temperature. Irradiance reduct-ions due to plants can reduce energy for space cooling.Vertical garden improves thermal insulation capacitythrough external temperature regulation (Stec et al.2005).

Since 1996, an observation has been conducted onthe surface temperature of vertical garden in differ-ent settings at the University of Toronto (Bass et al.2003). The results have consistently demonstrated thatamong the materials found in urban areas such as light-coloured brick, wall and black surface, vertical gar-den has cooler surface temperature. After that, a newround of testing was conducted comparing a verticalgarden with a light-coloured metal surface, which istypically found on roofs to shelter equipment. The pur-pose was not only to compare the temperature of thetwo surfaces (metal and leaf) but to also assess theshading potential of a vertical garden.

The shading effect of vertical greenery systems re-duces the energy used for cooling by approximately23% and 20% the energy used by fans, resulting inan 8% reduction in annual energy consumption (Basset al. 2003). Because in the fact, more thermal energyflows into the non-shaded walls due to direct exposureto the sun and resulted in higher surface wall temper-ature (Papadakis et al. 2001). Thermal behavior andeffectiveness of vegetation covers with different averageabsorption of solar radiation and diffusive properties(Takakura et al. 2000).

Nevertheless, toward interior thermal comfort, ver-tical garden gives an effect of increasing air humidity,which is create discomfort for building occupants, es-pecially in the evening (Widiastuti 2014).

3 MATERIALS AND RESEARCHMETHODOLOGY

3.1 Description of Vertical Garden Model

In this section the vertical garden will be described indetail, including planting system, irrigation and plantspecies.The kind of vertical garden used is geotextile system

that consists of an aluminum structure, a PVC panelinstalled on it, and felt layers. The plants are growingin the plant pockets which are always irrigated. Theycannot grow indefinitely because of the limited pocketspace, this is why it is not appropriate to apply plantswith large thick roots.A continuous watering system that functioning auto-

matically is needed. At the top and side of the verticalgarden is a flexible pipe for the irrigation. The waterflow through the nozzle and the distance between eachnozzle is 15 cm. Frequency of water flow depends onthe season, weather conditions and local climatologyconditions and orientation of the façades.The vertical garden is installed on an external not in-

sulated wall. The material of the wall is the bricks andthe thickness is 15 cm included internal and externalplaster. The plants used in the vertical garden modelare combination of various types of plants. They arePhalaenopsis sp., Dracaena warneckii and some of lo-cal climber plants. Detail of the vertical garden modelcan be seen in Figure 3.

3.2 Experiment Desription

The measurement on the experiment of the perfor-mance of vegetation-covered walls was conducted tovalidate the vertical garden model. The experimentconsisted of measuring the interior façade thermal per-formance of a building non-covered and covered with

Figure 3. Detail of vertical garden models

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plants in the Pertamina office building in Semarangcity, Central Java, Indonesia, as seen in Figure 4.One interior area of the façade oriented east, approx-

imately 4 m above the ground, was selected for themeasurements of vertical garden performance and oth-er interior area, approximately 10 m above the ground,in the same oriented façade was selected for measure-ment of bare wall (non covered vegetation), as seen inFigure 5. The interior spaces are non air-conditionedoffice space.The experiment was conducted during one day in

October 6, 2013; from early morning (06:00 am) un-til evening 18.00 (06:00 pm). The measurements werecollected at the 1 hour time intervals. The weatherconditions during the experiment are summarized in

Table 1.The following parameters were measured as individ-

ual points (variables) during the experiment:

1. Outdoor air temperature;2. Surface temperature of the interior wall behind

the bare façade;3. Surface temperature of the interior wall behind

the vegetated façade;4. Relative humidity;5. Wind speed near the façade.

The indoor-outdoor air temperature, relative humidi-ty and wind speed near the façade were measured 30 cmfrom the façade using 4 in 1 Environment Tester LM-8000. Wind speed measurements were made at a single

Figure 4. Location of experiment site, Pertamina branch office building, Semarang

Figure 5. Exterior side of field measurement

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Table 1. Weather conditions during the experiment

Values of weather condition Outdoor air temperature (C) Relative humidity (%) Wind speed (m/s)Highest values 35.2 64.5 1Average values 33 62.2 0.5Lowest values 29.5 58.2 0.3

point near vegetated façade. The surface temperatureswere measured using an infrared-surface thermometer.Instruments are visible in Figure 6.

Figure 6. Measurement instruments: (a) infraredsurface thermometer, (b) 4 in 1 enviro-nment tester LM-8000

Data collecting was done by two assistants at thesame time in every 1 hour.

3.3 Experimental Results and Analysis

The experimental day was in sunny condition. Table2, show the average, maximum and minimum values ofthe measured thermal properties. Bare and vegetatedfaçade temperature measured can be seen in Figure 7.The average interior surface temperature of the bare

façade was 32.7C, while of the vegetated façade was30.6C.The interior surface temperature of the vegetated

façade was always lower than bare façade (mean differ-ence is 2.1C). The peak interior surface temperature ofvegetated façade occurred around 15.00 (at 3:00 pm),(32.15C), while the bare façade occurred around 14.00(at 2:00 pm) (34.8C). This can be explained as ther-mal lag of the façade, which appears approximatelyduring one hour. Although the thermal lag was shortand it was not a focus of this study, it should be notedthat the effect of this thermal lag beneficial to reducecooling loads during peak hours.

4 DISCUSSION SURFACETEMPERATURE AND RESPOND TOWEATHER

4.1 Respond to Relative Humidity

When the relative humidity of air is low, plants signifi-cantly decreased the rate of evaporation and made tem-perature increased. Upon the relative humidity is high(at 14.00-18.00), the rate of evaporation from plantsgreatly increases. Its use heat from the air to evaporatewater. Automatically, its will reduce surface tempera-ture (at 14.00-18.00). It can be said that, decrease ofinterior surface temperature equal to relative humidity.The area of façade covered with vertical garden coolsbetter at higher humidity levels than bare façade, canbe seen in the Figure 8.

4.2 Respond to Outdoor Air Temperature

The interior façade surface temperatures generally in-creased in response to increasing air temperatures, Fig-ure 9. Even though surface temperature of the barefaçade was higher and closely matched with outdoorair temperature, but at higher air temperatures, thefaçade plant layer was also less effective in cooling theinterior façade surface temperature. It can be seen thatwhen outdoor air temperature increase, surface tem-perature of vegetated façade increase too. Therefore,it can be concluded that the effective thermal resis-tance of a plant layer gradually decreases when the airtemperature rises.

4.3 Respond to Wind Speed

Wind can improve the micro-climate and has a spe-cific effect in the building planning. Increasing windspeed aspect made the interior façade surface temper-ature decreased. It was happened because of heat fluxthrough convection. The faster air movement thenthe greater heat released (Frick and Suskiyatno 2007).Though, wind speed was low (average 0.5 m/s), but

Table 2. Measured thermal properties of the bare and vegetated façade

Measured façade properties Maximum Average MinimumBare wall interior surface temperature (C) 34.8 32.7 29.9Vegetated wall interior surface temperature (C) 32.15 30.6 28.5Difference in interior surface temperatures (C) (bare vs veg-etated wall)

4.4 2.1 0.2

Temperature difference between outside air temperature andinterior surface bare façade (C)

0.5 0.3 0

Temperature difference between outside air temperature andinterior surface vegetated façade (C)

4.8 2.4 0.3

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Figure 7. Temperature measurement of bare and vegetated façade

Figure 8. Temperature measurement of bare and vegetated façade respond to relative humidity

Figure 9. Temperature measurement of bare and vegetated façade respond to outdoor air temperature

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Figure 10. Temperature measurement of bare and vegetated façade respond to wind speed

when the wind speed increased (from 0.4 m/s to 0.8m/s and from 0.8 m/s to 1.0 m/s), the reduction ininterior façade surface temperature between bare andvegetated façade also increased, can be seen in Figure10.Since wind speed was low, vertical garden layer will

act as a buffer that keeps wind from moving alongon the building surface. Stagnant air made insulat-ing effect and significantly reduced the amount of heattransfer in the building. As a consequence, these effectsmade thermal inside the building material reduced andmade it cooler.

5 CONCLUSION

In this research, a field measurement performed thepurpose of studies about performance of thermal re-duction of surface temperature in the interior buildingfaçade by applying vertical garden.The first analysis was done with the result of mea-

surement the interior façade thermal performance ofvegetated façade and bare façade in the Pertaminabranch office building in Semarang city.The measurement demonstrated that the plant layer

on the façade can effectively reduced interior surfacetemperature on the façade. It can be seen from the in-terior surface temperature of the vegetated façade wasalways lower than bare façade. Thermal lag of vege-tated façade was also slower than bare façade, whichmeans beneficial to reduce cooling loads during peakhours.The second analysis was done with the result of re-

spond thermal performance to weather parameter. Themeasurement of the ambient temperature and humidi-ty confirm that the area of façade covered with verticalgarden cools better at higher humidity levels than barefaçade. When the outdoor air temperature increased,

surface temperature of vegetated façade also increased.The effective thermal resistance of a plant layer gradu-ally decreased when the air temperature rose. In otherhand, when the wind speed increased, the reduction ininterior façade surface temperature between bare andvegetated façade also increased. These effects madethermal inside the building material reduced and madeit cooler. It can be concluded that performance ofvertical garden influenced by the weather around thebuilding.

6 ACKNOWLEDGEMENT

We gratefully thank PT Pertamina Indonesia, branchoffice Semarang for giving the licence to conduct thisresearch using vertical garden application in its build-ing.

REFERENCES

Akbari, H., Kurn, D. M., Bretz, S. E., and Hanford,J. W. (1997). “Peak power and cooling energy sav-ings of shade trees.” Energy and Buildings, 25(2),139–148.

Bass, B., Liu, K., and Baskaran, B. (2003). “Evaluat-ing rooftop and vertical gardens as an adaptationstrategy for urban areas.” NRCC-46737 A020, In-stitute for Research and Construction, NationalResearch Council, Ottawa, Canada.

Dunnett, N. and Kingsbury, N. (2004). PlantingGreen Roofs and Living Walls. Timber Press, Port-land, Oregon, USA.

Frick, H. and Suskiyatno, B. (2007). Dasar-DasarArsitektur Ekologis. Kanisius, Yogyakarta, Indone-sia.

Holm, D. (1989). “Thermal improvement by means of

19

Widiastuti et al./International Journal of Architecture, Engineering and Construction 5 (2016) 13-20

leaf cover on external walls - a simulation model.”Energy and Buildings, 14(1), 19–30.

Johnston, J. and Newton, J. (2004). Building green:a guide to using plants on roofs. London EcologyUnit, London, UK.

Köhler, M. (2008). “Green facades - a view back andsome visions.” Urban Ecosystems, 11(4), 423–436.

McPherson, E. G., Herrington, L. P., and Heisler,G. M. (1988). “Impacts of vegetation on residen-tial heating and cooling.” Energy and Buildings,12(1), 41–51.

Papadakis, G., Tsamis, P., and Kyritsis, S. (2001).“An experimental investigation of the effect ofshading with plants for solar control of buildings.”Energy and Buildings, 33(8), 831–836.

Rashid, R., Ahmed, M. H. B., and Khan, M. S.(2010). “Natural green application technology onbuilding in Dense Dhaka City is provide a sustain-able, energy saving, comfortable and healthy envi-ronment.” Annual Asian Business Research Con-ference, BIAM, Dhaka Bangladesh.

Sharp, R. (2007). “Six things you need to knowabout green walls.” BD&C News, Availableat<http://www.bdcnetwork.com>.

Sharp, R., Sable, J., Bertram, F., Mohan, E.,and Peck, S. (2008). “Introduction to green walls:

technology, benefits & design.” Green Roofs forHealthy Cities, Toronto, Canada.

Stec, W., Van Paassen, A., and Maziarz, A. (2005).“Modelling the double skin façade with plants.”Energy and Buildings, 37(5), 419–427.

Takakura, T., Kitade, S., and Goto, E. (2000). “Cool-ing effect of greenery cover over a building.” En-ergy and Buildings, 31(1), 1–6.

Widiastuti, R., P. E. B. W. (2014). “Kenya-manan termal bangunan dengan vertical gar-den berdasarkan standar kenyamanan mom &wieseborn.” Jurnal Pembangunan Kota SemarangBerbasis Penelitian Sains & Teknologi, 8(1), 1–12.

Wong, N. H., Chen, Y., Ong, C. L., and Sia,A. (2003). “Investigation of thermal benefits ofrooftop garden in the tropical environment.”Building and Environment, 38(2), 261–270.

Wong, N. H., Tan, A. Y. K., Chen, Y., Sekar, K.,Tan, P. Y., Chan, D., Chiang, K., and Wong, N. C.(2010). “Thermal evaluation of vertical greenerysystems for building walls.” Building and Environ-ment, 45(3), 663–672.

Yeh, Y. P. (2010). Green Wall-The Creative Solu-tion in Response to the Urban Heat Island Effe-ct. National Chung-Hsing University, Taiwan.

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