Application of Green Façade as Passive

Cooling Technique for Energy Efficiency

Mohd Khairul Azhar bin Mat Sulaiman Architecture Department,

Faculty of Engineering and Built Environment, Universiti Kebangsaan Malaysia,

Bangi, Selangor, Malaysia. Institute Applied Climatology & Landscape Ecology,

Faculty of Biology, University of Duisburg-Essen, Essen, Germany.

m.khairulazhar@yahoo.com

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• Introduction • Objectives • Methodology • Findings • Conclusion

Contents

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Introduction

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Building Energy Efficiency can be improved by implementing

Active Energy Efficient strategies

Passive Energy Efficient strategies

Heating, Ventilation & Air-conditioning (HVAC) systems,

electrical lighting

Building envelope – insulation, material, shading devices, green

roof, green facade

Hong Kong (Cheung, C.K. et al., 2005) External insulation - Extruded polystyrene (EPS) Energy saving : 31.4% Peak load saving : 36.8%

Greece (Balaras C.A. et al, 2000) External shading ;i.e. awning and light-coloured roof & external wall Reduced space cooling load : 30%

Singapore (Wong et al, 2009) External shading - 100% coverage of Green Façade Reduced space cooling load : 17.93%

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• Government of Malaysia has announced, which ordered government offices to set an air-conditioning temperature no lower than 24° Celsius for optimum indoor thermal comfort and energy saving step. According to Ministry of Energy, Green Technology and Water, by lowering one degree (23° C) on air-conditioning thermostat, overall expenditure will increase from 4 to 7 per cent annually – BERNAMA, Malaysia National News Agency, reported on 11 August 2011

• Thus, this study is investigating on application of green façade as passive cooling technique for energy saving step on cooling period of office building.

Issue

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Overview of Vertical Greenery Systems

Direct Green Facade Indirect Green Façade – Cable & rod

Indirect Green Façade – Trellis/ Wiremesh

Indirect Green Façade – Perimeter flowerpot

Living wall – Geotextile felt Living wall - Panel

• Green façade (GF) is a vertical manner planting system rooted in the ground or planter pot, using supporting structure such as modular trellis, wire mesh or cable for climbing plants in screening exterior surface of building façade.

• As passive cooling technique in providing conducive indoor thermal environment and energy efficiency, GF acts as external shield offer shades to the building facade avoiding undesirable excessive radiation and reducing heat flux transfer through exterior surface (Chen, Li, and Liu 2013, Jim and He 2011).

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indoor indoor outdoor outdoor

solar radiation solar radiation

transmitted radiation

conventional wall Green Facade

cooling load cooling load

• However, a key factor to successful outcomes is depending on vegetation used in the system (Wong N.H. et al, 2003; Perez et al, 2009; Hodo-Abalo, S. et al, 2012, Fang C.F., 2008). Thus, a carefully decision on plant selection to be used is a crucial step to be taken for optimization on performance of the system.

• Furthermore, this step need to be engaged is to avoid frustration on the expectation of effectiveness of these systems as passive cooling technique.

• This study aimed to investigate performance of selected tropical climbing plants used on GF for energy efficiency on cooling load for office building. Selected tropical climbers used for this study are Thunbergia grandiflora and Argyreia nervosa.

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Research Objective • To investigate on energy saving of space cooling load for building attached

with Green Façade (GF) at eastern and western orientation walls using selected tropical climbers; Thunbergia grandiflora and Argyreia nervosa.

Research Methodology

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• 1st experiment : 8th June 2013 • Thunbergia grandiflora VS Control. • On sunny day, from 0800 - 1700hr. • Ave. ambient temperature : 31.7 °C • Ave. solar radiation : 324.9W/m² • Leaf area index (LAI) : 4.14 (east) and 4.08 (west) • Leaf size: 15cm (medium)

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Findings

• Energy savings:

17.2% per day • Peak load savings:

25.0% • Energy rate savings:

RM0.24/day

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Findings

• Energy savings:

15.2% per day • Peak load savings:

34.2% • Energy rate savings:

RM0.22/day

• 2nd experiment : 04th August 2013 • Argyreia nervosa VS Control. • On sunny day, from 0800 - 1700hr. • Ave. ambient temperature : 33.1 °C • Ave. solar radiation : 527.0W/m² • Leaf area index (LAI) : 3.72 (east) and 3.84 (west) • Leaf size: Ave. 25cm (large)

• Temperatures of the interior wall surface and indoor air are important parameters to evaluate the indoor thermal environment. Indoor surface temperature on east and west orientation walls of test cell with GF has a smaller temperature fluctuation comparing to control cell walls.

• Similar results were demonstrated on indoor air temperature fluctuation. It can be seen that the GF has a promising effect on stabilizing the indoor environment when the air conditioner is on. Consequently, it helps in reducing energy consumption for cooling loads.

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Findings

Thunbergia grandiflora Argyreia nervosa

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Thunbergia sp. (Kwatt)

Control (KWatt)

Indoor Thunbergia sp. (°C)

Indoor Control (°C)

mean 0.292 0.356 24.5 24.0max 0.387 0.530 25.0 24.9min 0.113 0.068 24.0 23.2stdev 0.087 0.110 0.27 0.46

Findings Thunbergia grandiflora VS Control.

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Thunbergia sp. (Kwatt)

Control (Kwatt)

Thunbergia sp. East In (°C)

Control East In (°C)

Thunbergia sp. West In (°C)

Control West In (°C)

mean 0.292 0.356 26.6 28.5 26.5 27.3max 0.387 0.530 28.0 30.3 28.1 29.7min 0.113 0.068 25.0 25.0 25.4 24.6stdev 0.087 0.110 1.03 1.68 0.99 1.53

Findings Thunbergia grandiflora VS Control.

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Findings

Argyreia sp. (Kwatt)

Control (Kwatt)

Argyreia sp.(°C)

Control (°C)

mean 0.3 0.4 24.6 24.8max 0.4 0.7 25.1 25.7min 0.0 0.1 24 24stdev 0.12 0.17 0.27 0.46

Argyreia nervosa VS Control.

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Findings

Argyreia sp. (Kwatt)

Control (Kwatt)

Argyreia sp. East In (°C)

Control East In (°C)

Argyreia sp. West In (°C)

Control West In (°C)

mean 0.3 0.4 26.8 29.2 26.7 27.7max 0.4 0.7 29.1 31.3 29.4 31.3min 0.0 0.1 25.0 24.7 25.0 25.0stdev 0.12 0.17 1.42 2.37 1.42 2.06

Argyreia nervosa VS Control.

• Previous results are indicated TG and AN were performed significantly for building energy efficiency. Both of climbers on GF were demonstrated able to reduce energy demand for cooling period.

• Next experiment was conducted to identify which climbers on GF is performed effectively in reducing energy consumption for cooling load within the same weather condition.

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Findings

• 3rd experiment : 28th August 2013 • Thungergia grandiflora VS Argyreia nervosa • On sunny day, from 0800 - 1700hr. • Ave. ambient temperature : 30.1 °C • Ave. solar radiation : 328.0W/m² • Ave. Leaf area index (LAI) : 4.11 (TG) and 3.78 (AN)

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Findings

• Energy savings of TG vs AN: TG save 5.2% per day than AN

• Peak load savings of TG vs AN : TG save 15.4% than AN

• Energy rate savings TG vs AN : TG save RM0.03/day rate than AN

• Results indicated both GFs were performed almost similar for building energy efficiency even though both climbers having a different LAI (TG; ave. LAI : 4.11 and AN; ave. LAI: 3.78). This is assumed of leaf size of AN (ave. 25cm) which can provides large area leaf surface coverage. However, TG was identified as most suitable climber for energy efficiency compared to AN due to higher energy saving.

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Conclusion • GF has a promising effect on building energy efficiency as passive technique

for cooling effect through shading on building envelope. GF is stabilizing the indoor environment when the air conditioner is on. Consequently, it helps in reducing energy consumption for cooling loads.

• Effectiveness of GF may perform significantly with suitable selection of climber on GF. In comparison to Thunbergia grandiflora and Argyreia nervosa, it was identified that TG is more suitable in providing benefit towards energy efficiency.

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Thank you