International Journal of Sustainable Built Environment (2016) 5, 387–399

HO ST E D BYGulf Organisation for Research and Development

International Journal of Sustainable Built Environment

ScienceDirectwww.sciencedirect.com

Original Article/Research

Potential of shading devices and glazing configurations oncooling energy savings for high-rise office buildings in

hot-humid climates: The case of Malaysia

Allen Khin Kiet Lau ⇑, Elias Salleh, Chin Haw Lim, Mohamad Yusof Sulaiman

Solar Energy Research Institute (SERI), Universiti Kebangsaan Malaysia, 43600 Bangi, Malaysia

Received 1 February 2016; accepted 28 April 2016

Abstract

Rapid growing of energy use has raised critical concerns over energy supply difficulties and negative environmental impacts globallyand among ASEAN countries. Malaysia is experiencing a high average annual energy demand growth rate of approximately 2.3% whichlarge portion of that energy is used by office buildings. Under the hot-humid climatic conditions in Malaysia, high-rise office buildingswith large or fully glazed facades are facing a major problem of overheating due to high solar radiation through the glazed facades. Thishas caused high cooling energy requirements. The aim of this study is to investigate the potential of three types of shading devices oncooling energy savings when applied at different facade orientations. The aim also extends to investigations on different cooling energysavings when shading devices are applied on facade glazing with different configurations and thermal performances. This was donethrough a case study of a high-rise office building in Kuala Lumpur, Malaysia using IES (VE) building thermal simulation software.Twenty simulation building models were applied with different shading devices at different facade orientations and with high and lowperformance facade glazing. The simulation results indicate that high-rise office buildings in Malaysia use approximately 45.9% of totalbuilding energy for cooling purposes. The results also suggest that use of various shading devices on low-e double glazed facades willresult between 1.0% and 3.4% annual cooling energy savings, depending on the types of shading devices and facade orientations. Theestimated annual cooling energy savings increase to between 5.0% and 9.9% when the shading devices are applied to all orientationsof low-e double glazed facades. The estimated annual cooling energy savings further increase to between 5.6% and 10.4% when the facadeglazing is replaced by single clear glazing. This study recommends prioritizing shading devices on the East and West facades for opti-mized annual cooling energy savings. The simulation results show that egg-crate shadings are able to produce the highest annual coolingenergy savings compared to vertical shadings and horizontal shadings. It is recommended to use shading devices on low performanceglazing compared to high performance glazing since the energy savings are more significant when shading devices are used on low per-formance glazing. In conclusion, the use of shading devices is more effective in achieving cooling energy savings compared to the use ofhigh performance glazing under the hot-humid climate of Malaysia.� 2016 The Gulf Organisation for Research and Development. Production and hosting by Elsevier B.V. This is an open access article under the CCBY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Keywords: Cooling energy; High-rise office building; Hot-humid climate; Shading devices

http://dx.doi.org/10.1016/j.ijsbe.2016.04.004

2212-6090/� 2016 The Gulf Organisation for Research and Development. Production and hosting by Elsevier B.V.

This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

⇑ Corresponding author at: No. 1, Jalan Simpoh, 96000 Sibu, Sarawak, Malaysia. Tel.: +97 1508252263.

Peer review under responsibility of The Gulf Organisation for Research and Development.

Table 2Statistics of electricity use in Malaysia, 2013. Source: Energy CommissionMalaysia, 2013.

Sector Consumption coverage, %

Agriculture 0.3Commercial 32.7Industrial 45.4Residential 21.4Transport 0.2

388 A.K.K. Lau et al. / International Journal of Sustainable Built Environment 5 (2016) 387–399

1. Introduction

Rapid growing of energy use is a major issue at the glo-bal perspective with concerns over supply difficulties,exhaustion of energy resources and environmental impacts(Perez-Lombard et al., 2008). According to InternationalEnergy Agency, the energy use growing trend is also verycritical among ASEAN countries. As shown in Table 1,an average annual energy demand growth rate of 2.5% ispredicted between the year of 2011–2035. In the case ofMalaysia, the predicted growth rate is 2.3%. The same datapredicted that Malaysia will experience an increase of29.7% of energy demand from 2011 to 2020, with an aver-age annual growth rate of 3.3% (Birol, 2013).

Buildings consumed up to 40% of total energy globally(Hassan et al., 2014). In the context of Malaysia, buildingsconsumed a total of 48% of the electricity generated in thecountry (Chua and Oh, 2011). According to Energy Com-mission Malaysia, commercial buildings consumed a highpercentage of 32.7% of total energy used in the countryin 2013 (Energy Commission Malaysia, 2016). This isbecause commercial buildings in hot-humid climates suchas is found in Malaysia are often installed with air condi-tioning and mechanical ventilation systems to sustain andimprove indoor thermal comfort. Most of the time, thesesystems consume the most energy among all other buildingservices (Kwong et al., 2014). Other sectors includingindustrial, residential, agricultural and transport consumed45.4%, 21.4%, 0.3% and 0.2% of electricity respectively, asshown in Table 2.

1.1. Hot-humid climate of Malaysia

Malaysia is positioned on the South China Sea. Thiscountry lies between 1� and 7� in North latitude, and100� and 120� in East longitude (Nugroho, 2010). Malaysiais experiencing hot-humid climatic conditions with charac-teristics of uniform temperature, high humidity and copi-ous rainfall. Malaysia naturally has abundant sunshineand thus abundant solar radiation throughout the year(Ministry of Science, Technology and Innovation(MOSTI), 2015). Malaysia receives an average solar radia-tion of 400–600 MJ/m2 per month (Mekhilef et al., 2012).The annual average solar radiation (MJ/m2/day) is shownin Fig. 1. Table 3 shows the yearly average solar radiationlevels throughout different cities in Malaysia.

Table 1Primary energy demand by ASEAN countries (Mtoe). Source: International E

1990 2011 2020

Indonesia 89 196 252Malaysia 21 74 96Philippines 29 40 58Thailand 42 118 151Rest of ASEAN 42 119 161

Total ASEAN 223 549 718

Due to geographical position, temperature in Malaysiatypically varies from 24 �C to 34 �C and is rarely below23 �C or above 35 �C, as shown in Fig. 2. The relativehumidity varies from 54% to 96% over the course of theyear and rarely drops below 44% or reaches 100%(Weatherspark, 2016). The weather conditions in Malaysiais such that it is a rare circumstance to witness days com-pletely without sunshine except during the Northeast mon-soon season and it is unusual to witness a whole day with aclear sky in drought season (Mirrahimi et al., 2016). Thereare two types of monsoons that occur yearly, namelyNortheast monsoon and Southwest monsoon. Northeastmonsoon occurs between November and March. Mean-while, the Southwest monsoon occurs between May andSeptember. Winter-monsoon occurs during April andOctober and between September and December. Malaysiaexperiences heavy rainfall with the measurement of2500 mm per year.

1.2. Problem of high cooling energy consumption due to

overheating

Highly glazed buildings have become a worldwidedesign trend in modern architecture for any climate(Chown et al., 2010). In developing countries includingMalaysia, huge facade glazing has been widely used to pre-sent positive architectural images such as transparency andmodernity. Besides, huge facade glazing can also providefull external views. However, this causes higher energy con-sumption and thermal discomfort due to higher solar gain(Hien et al., 2005). From previous studies, high-rise build-ings in hot-humid climate are experiencing overheating dueto high solar radiation. Large glazed facades are said to bethe main cause of this problem (Ling et al., 2007; Kirimtataet al., 2016). Due to the overheating condition caused by

nergy Agency IEA, 2013.

2025 2035 Average Annual GrowthRate (2011–2035) (%)

282 358 2.5106 128 2.369 92 3.5168 206 2.3178 221 2.6

804 1004 2.5

Figure 1. Annual average solar radiation (MJ/m2/day). Source: Mekhilef et al., 2012.

Table 3Yearly average solar radiations in Malaysia. Source: Mekhilef et al., 2012.

S/I Region/cities Annual average solarradiation, kW h/m2

1 Kuching 14702 Bandar Baru Bangi 14873 Kuala Lumpur 15714 Petaling Jaya 15715 Seremban 15726 Kuantan 16017 Johor Bahru 16258 Senai 16299 Kota Baru 170510 Kuala Terengganu 171411 Ipoh 173912 Taiping 176813 George Town 178514 Bayan Lepas 180915 Kota Kinabalu 1900

Figure 2. Daily average low (blue) and high (red) temperatures inMalaysia. Source: Weatherspark, 2016.

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high solar radiation through largely glazed facades, officebuildings in Malaysia consume between 200 and250 kW h/m2/year of energy of which about 64% is forair conditioning, 12% for lighting and 24% for general

equipment (Chan, 2009). Another study showed that airconditioners are the major energy users in office buildingsin Malaysia with 57% energy usage. This is followed bylighting 19%, lifts and pumps 18%, and other equipment6% (Saidur, 2009).

1.3. Aim of study

This study has identified the problem of overheating asthe cause of high cooling energy consumption of high-riseoffice buildings in Malaysia. It is noticed that this problemis due to high solar radiation through highly glazed build-ing facades under the hot-humid climatic conditions. Build-ing surfaces with direct exposure to the sun throughwindows, walls and roofs can admit heat from solar radia-tion. This leads to an increase in the amount of energyneeded for cooling purposes. To avoid the inflow of heat,the surfaces on which the sun’s rays fall must be protected.Emphasis must be given to shading devices because glazedwindows are the main components which allow the pene-tration of incoming heat and consequently increase the riskof overheating (Datta, 2001). Previous study suggested thatshading elements must be carefully integrated and consid-ered at an early design stage as the use of shading devicesis vital for facades with large, glazed portions in the senseof energy conservation in buildings (Kirimtata et al., 2016).

From the identified problems, there are always questionsregarding types of appropriate shading devices to be usedon specific facade orientation for maximized solar heatgain reduction. Besides, there are questions regarding dif-ferent energy saving implications of shading devices onglazing with different configurations and thermal perfor-mances. These questions formed the point of departurefor this study. Therefore, the aim of this study is to inves-tigate the potential of shading devices on cooling energysavings of high-rise office buildings in Malaysia. The focusof this study is on the effect of different types of shadingdevices on each facade orientation, in terms of coolingenergy savings. However, in order to further challenge on

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this issue, the focus of this study extends to the effect ofvarious shading devices on cooling energy savings ofhigh-rise office buildings with different facade glazing con-figurations and thermal performances. It is the aim of thisstudy that the results and recommendations can be usefulguidelines for facade designers not only in choosing appro-priate shading devices for each specific facade orientation,but also to understand the energy saving aspect of variousshading types when used on facade glazing with differentconfigurations and thermal performances. This is usefulwhen deciding between low performance glazing with shad-ing devices and high performance glazing with or withoutshading devices.

2. Literature review

Building Energy Intensity BEI is an index used in thecalculation of building energy consumption over a periodof one year. According to Malaysia Standard MS 1525:2014 Code of Practice on Energy Efficiency and Use ofRenewable Energy for Non-Residential Buildings, BEIshows the total energy consumed in one year in kilowatthours in every square meter area of the building. It is mea-sured in kWh/m2/year. MS 1525: 2014 recommended a BEIof not more than 180 kW h/m2/year for non-residentialbuildings in Malaysia (Department of StandardMalaysia, 2014). In the case of green building rating toolin Malaysia, Green Building Index GBI was set up in2009 as a strong operator for energy efficiency in building.Since implemented, it has positively influenced buildingenergy efficiency practices in Malaysia (Pir Mohammadiet al., 2013). Under the GBI rating tool, buildings will beassessed and awarded based on six main design criteria.They are Energy Efficiency (EE), Indoor EnvironmentalQuality (EQ), Sustainable Site Planning & Management(SM), Material and Resources (MR), Water Efficiency(WE) and Innovation (IN). The assessment criteria andallocated points are shown in Table 4. GBI Non-Residential New Construction rating tool requires build-ings to achieve a BEI of not more than 150 kW h/m2/yearunder the Energy Efficiency (EE) assessment criteria (GBIAssessment Criteria for Non-Residential NewConstruction (NRNC), 2016). Both MS 1525: 2014 recom-mendation and GBI requirements on the BEI have been

Table 4GBI Non-Residential New Construction assessment criteria. Source:Green Building Index, 2016.

S/N Assessment criteria Max points

1 Energy efficiency (EE) 352 Indoor environment quality (EQ) 213 Sustainable site planning & management (SM) 164 Materials & resources (MR) 115 Water efficiency (WE) 106 Innovation (IN) 7

Total 100

used as acceptable benchmarks on energy consumption ofhigh-rise office buildings in Malaysia.

From a previous study, external shading devices arereferred to as the most effective ones comparing to internalshadings (since in this case, all the heat has already enteredthe space) (Offiong and Ukpoho, 2004). From that study,fixed external shading devices are feature of the architec-ture of the tropics. However, they are used less in temper-ate climates. In opposite, vertical shading devices are usedextensively in temperate climates. That study also men-tioned that simultaneous horizontal and vertical shadingdevices are used in the form of egg-crate shading devices.

In the context of Malaysia, a research paper has dis-cussed the measurement of indoor temperature and relativehumidity for an office room with three different types ofshading devices namely vertical shading devices, horizontalshading devices and egg-crate shading devices. Indoor tem-perature and relative humidity equipment (HOBO DataLogger) was used in that study. The objective of that studywas to find out a suitable shading type for achieving ther-mal comfort in an office building. The results indicated thategg-crate shading devices have significant impact ondecreasing indoor temperature as well as discomfort hourscompared with other shading types (Arifin and Denan,2015). Another study on potential of shading devices fortemperature reduction in high-rise residential buildings inMalaysia suggested that external shading devices such asoverhangs, louvers, and egg-crates should be encouragedas architectural elements to protect building envelopesand occupants from solar radiation. The computer simula-tion results using IES (VE) showed that shading devices inboth ventilated and unventilated rooms have a significantimpact on improving internal thermal conditions. How-ever, egg-crate devices are the best in reducing indoor airtemperature and decreasing the number of discomforthours because of their configuration i.e., combination ofoverhangs and fins. The egg-crate devices avoid solar radi-ation from varied sun angles (Al-Tamimia and Fadzil,2011).

In regard to the thermal performance and energy use, arecent research studied the effects of shading devices onthermal performance of office buildings in many cities withdifferent latitude and climatic conditions. The studyshowed that shading devices have a great impact on energysavings and are able to improve thermal performance ofoffice buildings (Palmero-Marrero and Oliveira, 2010).Another previous research studied the effectiveness ofshading devices on cooling energy savings for East andWest windows of residential buildings in Singapore. Thestudy showed that under hot-humid climate, 2.62–3.24%of energy cooling load can be saved by applying a simple30 cm deep horizontal shading device to the window. Whenthe depth of the shading devices reached 60 cm, 5.85–7.06%of the cooling load could be saved. When the depth of theshading devices reached 90 cm, the cooling load of theroom was reduced by 8.27–10.13% (Wong and Li, 2007).Another previous study on a high-rise residential building

Figure 3. Case study building.

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in Taiwan indicated that envelope shading is the best strat-egy to decrease cooling energy consumption, whichachieved savings of 11.3% on electric consumption (Yuet al., 2008).

A previous research carried out a study with simulationson the thermal performances of a building with design vari-ables on building envelope and optimizations of window-shading devices (Bouchlaghem, 2000). Another researchused Ombre software to evaluate the influence of the geom-etry of window-shading devices on the building thermalperformance (Corrado et al., 2004). There were also manyother studies on external facade shadings covering differentclimate zones using IES (VE) as building thermal simula-tion tools (Kim et al., 2012; Hammad and Abu-hijleh,2010; Freewan, 2014).

In recent years, many researches were carried out tostudy different types of external building facade shadingsand their effects on indoor air temperature, indoor thermalcomfort and energy consumption. However, it is the chal-lenge of this study to further investigate the potential ofvarious shading devices on cooling energy requirementsof high-rise office buildings in Malaysia not only in relationto different facade orientation, but also in relation tofacade glazing with different configurations and thermalperformances. This contributes to previous studies by pro-viding guidance to designers in deciding between low per-formance facade glazing with appropriate shading devicesand high performance facade glazing with or without shad-ing devices.

3. Methodology

3.1. Simulation software

Integrated Environmental Solutions Virtual Environ-ment IES (VE) was selected as the simulation softwarefor this study. The selection was made based on the com-parisons of various building thermal simulation softwareon their capabilities, user-friendly and accuracy aspects.IES (VE) provides a variety of variables for analysis as wellas output graphical forms in simulation of buildings. Theprogram provides an environment for the detailed evalua-tion of building and system designs, allowing them to beoptimized with regard to comfort criteria and energy use(Drury et al., 2005). Previous studies have recommendedthat IES (VE) is with high accuracy because from previousresearch analysis findings, it was concluded that there wasno considerable statistical difference in the mean valuesbetween IES (VE) simulated results and measured data(Chinnayeluka, 2011). The readily available Kuala Lumpurweather data from IES (VE) itself was used in all the sim-ulations in this study.

3.2. The case study building

There is no national building code or guidelines definingthe minimum height or number of floors of high-rise build-

ings in Malaysia. Therefore, the definition of high-risebuilding in this study is based on International BuildingCode IBC 2009 as well as National Fire Protection Associ-ation NFPA code. Both codes define high-rise buildings asbuildings with a minimum height of 75 feet (22.9 m) aboveground level. Referring to typical office buildings’ floorheight of approximately 3.8 m in Malaysia, 22.9 m is theheight of a seven-floor office building. Therefore, the min-imum number of floors acceptable as high-rise in this studyis seven.

A high-rise office building located at Jalan MunshiAbdullah, Kuala Lumpur was selected as the case studyhigh-rise office building because it has more than 7 floorsand the building facades are fully glazed with WWR of1.0 as shown in Fig. 3. This represents the modern facadedesign trend of office buildings in Malaysia. Furthermore,the fully glazed facades are suitable to be used as base casebuilding model so that this building model can be dupli-cated and applied with various external shading devicesfor simulations on cooling energy consumptions. Thisbuilding consists of a 4-story high entrance lobby with 41floors of occupied office levels. The floor-to-floor heightis 4000 mm. Each floor has an efficient floor plate of1393.55 m2. The total building gross floor area is72,000 m2. It has a rectangular building foot print withNorth–South building orientation. The design utilizesperimeter of the tower as office spaces whereas the servicezone is located at the center of the tower which includemechanical/electrical rooms, toilets, pantry and verticaltransportation such as lifts and fire staircases as shown inFig. 4.

3.3. Construction materials of case study building

The case study high-rise office building was constructedin the IES (VE) software based on the actual building spec-ifications and construction materials. The model is shownin Fig. 5. Summary of the specification for the buildingmodel is shown in Table 5. The case study building hasfully glazed facades facing all 4 orientations. The buildingenvelope comprises curtain wall system with aluminumframes and is set out on 1160 mm grid. The curtain wallis constructed of double glazed panels with low-e glass.

Figure 4. Case study building typical floor layout.

Figure 5. Case study building model constructed in IES (VE).

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3.4. Types of shading devices for simulations

Due to geographical location, most of office buildings inMalaysia are facing problem of how to prevent direct sunlight especially from East and West. This part of studyinvolved simulations of three types of shading devicesnamely horizontal shading, vertical shading and egg-crateshading. In order to investigate the effects of these shadingdevices on each facade orientation in regard to coolingenergy savings, the three types of shading devices were

Table 5Summary of case study building specifications.

Description Building design/material

Number of floors 42Total gross floor area 72,000 m2

Floor-to-floor height 4000 mmOccupancy load 10 m2/personRoof construction RC slab with water membInternal ceiling and floor construction Raised floor system aboveWindow to wall ratio 1.0External glazing Double layers of laminateIndoor temperature 23 �CAir conditioning system Chilled water cooling withLighting system 400 LUX – Public Area,

400 LUX – Lift lobbies, 1

applied on North, East, South and West facades separatelyfor simulations of annual building and cooling energy con-sumption. The width of the shading devices was fixed at600 mm as recommended by many studies conducted inthe tropics with considerations on day lighting, estheticand the view angle requirements from the internal spaces(Al-Tamimia and Fadzil, 2011; Liping and Hien, 2007).There were total 13 simulations carried out for this pur-pose. The different types of shading devices are shown inFig. 6.

3.5. Types of facade glazing configurations for simulations

As mentioned earlier, the focus of this study is on theeffect of different types of shading devices on each facadeorientation in terms of cooling energy savings. However,the focus extends to further challenge this issue with refer-ence to different facade glazing configurations i.e. high per-formance and low performance facade glazing. In this partof simulation, the high performance double glazed facadesof the base case building model were replaced by low per-formance 6 mm single clear glazing with Shading Coeffi-cient 0.9 and U-value 6.38 W/m2 k. There were 6simulations carried out by applying horizontal shadings,vertical shadings and egg-crate shadings on the facades ofbuilding models with double glazing and single glazingfor comparisons on cooling energy savings. With this, weare able to understand the energy saving effects of variousshading types on different facade glazing types.

4. Results and discussion

4.1. Monthly building and cooling energy consumption of

base case model with double glazing

The simulation results on monthly building energy con-sumption of the base case model are shown in Fig. 7. Theresults indicated the lowest monthly energy consumption of675.59 MW h in February. On the contrary, the resultsindicated the highest monthly building energy consumptionof 787.47 MW h in July. The difference between the lowestand the highest monthly energy consumptions is

rane insulation covered with concrete paversRC slab with air plenum and suspended ceiling below slab

d low-e glazing, Shading Coefficient 0.4, U-value 3.35 W/m2 k

23 VAV boxes in every floor400 LUX – Ground floor, 300 LUX – Corridor, 200 LUX – Staircases,00 LUX – Car park, 250 LUX – Lift, 400 LUX – Office Area

Without shading(base case)

Horizontal shading Vertical shading Egg-crate shading

Figure 6. Types of shading devices for energy simulations.

Figure 7. Monthly building energy consumption of base case model.

Figure 8. Monthly cooling energy consumption of base case model.

A.K.K. Lau et al. / International Journal of Sustainable Built Environment 5 (2016) 387–399 393

Tab

le6

Annual

buildingenergy

consumption,coolingenergy

consumptionan

dBEIbydifferentshad

ingdevices

atdifferentfacadeorientations.

Typ

eofshad

ing

Annual

buildingenergy

consumption,MW

hAnnual

coolingenergy

consumption,MW

hBuildingenergy

intensity

BEI,kW

h/m

2/year

NE

SW

NE

SW

NE

SW

NoShad

ing

8963.9

8963

.989

63.9

8963.9

4111

.241

11.2

4111.2

4111

.212

4.5

124.5

124.5

124.5

Horizontal

8872.9

8893.1

8893.2

8836.9

4069.8

4052.4

4068.8

4052.2

123.2

123.5

123.5

122.7

Vertical

8858.6

8840

.688

43.1

8793.3

4039

.540

14.3

4031.0

4023

.112

3.0

122.8

122.8

122.1

Egg

-crate

8790.2

8781

.688

05.6

8701.7

4005

.739

75.4

4006.0

3972

.112

2.1

122.0

122.3

120.9

N=

North,E=

East,S=

South,W

=West.

394 A.K.K. Lau et al. / International Journal of Sustainable Built Environment 5 (2016) 387–399

111.88 MW h. As shown in Fig. 8, the lowest monthlycooling energy consumption of 304.43 MW h was shownin February too. Meanwhile, the highest monthly coolingenergy consumption was shown in May with364.91 MW h. Simulation results indicated difference of60.48 MW h between the lowest and highest monthly cool-ing energy consumption. From the simulation results ofannual building energy and annual cooling energy con-sumption of 8963.89 MW h and 4111.16 MW h respec-tively, 45.9% of building energy was used for coolingpurposes annually.

4.2. Annual building energy consumption, annual cooling

energy consumption and BEI by different shading devices atdifferent facade orientation with double glazing

From the analysis of the simulated results, base casebuilding model without any shading devices resulted anannual building energy consumption of 8963.9 MW h withBEI 124.5 kW h/m2/year. Horizontal shadings on the Westfacade resulted in the lowest annual building energy con-sumption of 8836.9 MW h with BEI 122.7 kW h/m2/year.Meanwhile, applying the same shading devices on theSouth facade resulted in the highest annual building energyconsumption of 8893.2 MW h with BEI 123.5 kW h/m2/year. Application of vertical shadings on the West facaderesulted in the lowest annual building energy consumptionof 8793.3 MW h with BEI 122.1 kW h/m2/year. Mean-while, application of such devices on the North facaderesulted in the highest annual building energy consumptionof 8858.6 MW h with BEI 123.0 kW h/m2/year. When bothhorizontal and vertical shading devices were combined asegg-crate shading devices, application of such devices onthe West facade resulted in the lowest annual buildingenergy consumption of 8701.7 MW h with BEI120.9 kW h/m2/year. Meanwhile, application of the samedevices on the South facade resulted in the highest annualbuilding energy consumption of 8805.6 MW h with BEI122.3 kW h/m2/year. As shown in Table 6, building modelwithout any shading devices resulted in an annual coolingenergy consumption of 4111.2 MW h. Horizontal shadingson the West facade resulted in the lowest annual coolingenergy consumption of 4052.2 MW h. Meanwhile, apply-ing the same shading devices on the North facade resultedin the highest annual cooling energy consumption of4069.8 MW h. Application of vertical shadings on the Eastfacade resulted in the lowest annual cooling energy con-sumption of 4014.3 MW h. Meanwhile, application of suchdevices on the North facade resulted in the highest annualcooling energy consumption of 4039.5 MW h. When bothhorizontal and vertical shading devices were combined asegg-crate shading devices, application of such devices onthe West facade resulted in the lowest annual coolingenergy consumption of 3972.1 MW h. Meanwhile, applica-tion of the same devices on the South facade resulted in thehighest annual cooling energy consumption of4006.0 MW h (Fig. 9).

Figure 9. Annual cooling energy consumption by different shading devicesat different facade orientations – double glazing.

A.K.K. Lau et al. / International Journal of Sustainable Built Environment 5 (2016) 387–399 395

4.3. Annual cooling energy savings by different shading

devices at different facade orientation with double glazing

The simulation results of the 13 building models withdifferent types of shading devices at different facade orien-tation were analyzed in regard to the annual cooling energy

Figure 10. Annual cooling energy savings

Figure 11. Monthly building energy consumption by different

savings. Fig. 10 indicated egg-crate as the best shading typefor optimum cooling energy savings. This is followed byvertical shading and lastly horizontal shading. The highestsavings of 3.4% was estimated by applying egg-crate shad-ings on the West facade; 3.3% savings on the East facade;and 2.6% savings on the North and South facades. Use ofhorizontal shading devices resulted in annual energy sav-ings of 1.4% on East and West facades, and 1.0% on Northand South facades. Vertical shading devices resulted inannual cooling energy savings between 1.7% and 2.4% atdifferent facade orientations, as shown in Fig. 10. As shownin the same Fig. 10, egg-crate shading devices resulted in3.4% of energy savings on the West facade and 3.3% energysavings on the East facade comparing to only 2.6% energysavings on the North and South facades. Similarly, verticalshadings resulted in higher energy savings of 2.4% on theEast facade and 2.1% energy savings on the West facadecomparing to only 1.9% and 1.7% energy savings on theSouth and North facades respectively. Higher energy sav-ings of 1.4% was estimated by having horizontal shadingdevices on West and East facades comparing to only1.0% of energy savings on North and South facades.

by different types of shading devices.

shading devices on all facades – single and double glazing.

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4.4. Comparisons of monthly building energy consumption,

monthly cooling energy consumption, BEI and annual

cooling energy savings by different shading devices at all

facades with double and single glazing

The simulations and analysis above focused on coolingenergy savings by different shading types on differentfacade orientations with double glazing. The following sim-ulations and analysis extended the focus to comparisons ofthe cooling energy savings by different shading types on allfacades but with different glazing configurations i.e. highperformance double low-e glazing and single 6 mm clearglazing. From the simulated results shown in Figs. 11and 12, egg-crate shadings resulted in the lowest monthlybuilding and cooling energy consumption in every monthof the year compared to horizontal and vertical shadings.This is for both cases of double glazing and single glazing.The results showed February as the month with the lowestbuilding and cooling energy consumption while highenergy consumption was shown between March and July.The BEI of the base case building model with double glaz-ing and without any shading was reduced from124.5 kW h/m2/year to 116.5 kWh/m2/year when egg-crate shadings were applied to all the facades. This resultedin annual cooling energy savings of 9.9% as shown inTable 7. The use of horizontal shadings however reducedBEI to 118.3 kW h/m2/year with annual cooling energysavings of 7.4%. Vertical shadings reduced BEI to120.4 kW h/m2/year with annual cooling energy savingsof 5.0%. When single 6 mm clear glazing was used toreplace the double glazing without any shading, BEI wasincreased from 124.5 kW h/m2/year to 135.7 kW h/m2/year. The BEI was however reduced to 127.2 kW h/m2/yearwith annual cooling energy savings of 10.4% when egg-crate shadings were applied to all the facades. The use ofhorizontal shadings reduced BEI to 129.3 kW h/m2/yearwith annual cooling energy savings of 7.8%. Vertical shad-ings reduced BEI to 131.2 kW h/m2/year with annual cool-ing energy savings of 5.6%.

Figure 12. Monthly cooling energy consumption by different s

5. Discussion

The simulated annual building energy consumption of8963.89 MW h for the base case building model indicateda BEI of 124.5 kW h/m2/year. This is meeting the MS1525: 2014 recommended BEI benchmark of not more than180 kW h/m2/year for non-residential buildings in Malay-sia, as well as the GBI BEI requirements of not more than150 kW h/m2/year. The simulated BEI is considered lowcompared to an average BEI of 200–250 kW h/m2/yearfor office buildings with low glazing specifications inMalaysia (Chan, 2009). This is most probably due to theuse of high performance double glazing with low-e coatingswhich allow penetration of visible light of the solar spec-trum and block the other wavelengths that are generallyresponsible for solar heat gains (Robinson and Hutchins,1994). However, the BEI was increased to 135.7 kWh/m2/year when single glazing was used. This is due to thelow specification of the 6 mm single clear glazing withoutany low-e coating and with high U-value of 6.38 W/m2 k.

When different types of shading devices were added tothe base case building model, it was found that differenttypes of shading devices resulted in different cooling energyrequirements although they were placed at the same facadeorientation. Use of same shading devices on differentfacade orientations also resulted in different amounts ofannual cooling energy savings. It is noticed that applicationof all the three types of shading devices on West and Eastfacades in general resulted in higher annual cooling energysavings compared to North and South facades. This isbecause buildings in Malaysia receive higher solar radia-tion from Eastern and Western sun during morning andevening due to the geographical position of the country(Al-Tamimia et al., 2011). Another reason is due to therectangular shape of the building with a North–South ori-entation. This caused the effect of shading devices on BEIand energy savings to be more significant as these twofacades have larger areas exposed to direct sun light andsolar radiation. The simulation results indicated that

hading devices on all facades – single and double glazing.

Tab

le7

Annual

buildingenergy

consumption,an

nual

coolingenergy

consumption,BEIan

dan

nual

coolingenergy

savings

bydifferentshad

ingdevices

atallfacades

withsinglean

ddouble

glazing.

Energy

savings

Noshad

ing

Horizontalshad

ing

Verticalshad

ing

Egg

-crate

shad

ing

Singleglazing

Double

glazing

Singleglazing

Double

glazing

Singleglazing

Double

glazing

Singleglazing

Double

glazing

Annual

buildingenergy

consumption,

MW

h97

71.3

8963

.993

08.3

8520.7

9445

.086

68.9

9158

.583

89.4

Annual

coolingenergy

consumption,MW

h46

24.2

4111

.242

61.7

3807.9

4365

.439

07.3

4145

.037

06.5

Buildingenergy

intensity,BEI

135.7

124.5

129.3

118.3

131.2

120.4

127.2

116.5

Annual

coolingenergy

savings,MW

h0

036

2.5

303.3

258.9

203.9

479.2

405.0

Annual

coolingenergy

savings,%

0.0%

0.0%

7.8%

7.4%

5.6%

5.0%

10.4%

9.9%

A.K.K. Lau et al. / International Journal of Sustainable Built Environment 5 (2016) 387–399 397

egg-crate shadings resulted in lower annual cooling energyconsumption compared to vertical and horizontal shad-ings. The simulated annual cooling energy savings of notmore than 3.4% is not significant. This is due to the highperformance double glazing with low-e coatings used bythe case study building, which minimized solar heat radia-tion to internal spaces (Robinson and Hutchins, 1994). Useof any types of shadings on double glazing resulted inlower annual building and cooling energy requirementscompared to the same type of shadings used on single glaz-ing. However, it is important to note that the use of anytypes of shadings on single glazing resulted in a higher per-centage of annual cooling energy savings compared to thesame type of shadings used on double glazing.

From the analysis of the simulation results involved dif-ferent shading devices at different facade orientations anddifferent glazing configurations, selection of appropriateshading types for specific facade orientation can be priori-tized. The impact of different shading devices and differentglazing configurations on cooling energy savings can alsobe analyzed. The analysis of the simulated results producedconclusions and recommendations that enabled theachievement of the aim of this study i.e. to help facadedesigners not only in choosing appropriate shading devicesfor each specific facade orientation, but also to understandthe energy saving aspect of various shading types whenused on facade glazing with different configurations andthermal performances.

6. Conclusions and recommendations

From the analysis of the IES (VE) simulation results onannual building and cooling energy consumption of thecase study building, it can be suggested that high rise officebuildings in Malaysia use approximately 45.9% of totalbuilding energy for cooling purposes. This study also sug-gests that use of various shading devices on different facadeorientations with low-e double glazing will result in annualcooling energy savings, ranging from 1.0% to 3.4%. Theannual cooling energy savings are expected to increase tobetween 5.0% and 9.9% if the shading devices are appliedto all facades of the same low-e double glazing. However,it is important to note that the annual cooling energy sav-ings are expected to be further increased to between 5.6%and 10.4% when the shading devices are applied to allfacades with single clear glazing.

Major conclusions and recommendations of this studycan be made as below:

1. It is recommended to apply shading devices on facadesof high-rise office buildings in Malaysia for coolingenergy savings.

2. Egg-crate shading devices are able to result in higherannual cooling energy savings compared to verticalshading and horizontal shading under hot-humidclimates.

398 A.K.K. Lau et al. / International Journal of Sustainable Built Environment 5 (2016) 387–399

3. Applying shading devices on the West and East facadeswill result in higher annual cooling energy savings com-pared to North and South facades under hot-humidclimates.

4. Applying shading devices on low performance singleclear glazing will result in higher annual cooling energysavings compared to high performance low-e doubleglazing.

In order to achieve the aims of this study, it is recom-mended that facade designers prioritize and apply appro-priate types of shading devices on specific facadeorientation on high-rise office buildings in Malaysia formaximized cooling energy savings. It is also recommendedthat facade designers consider the different cooling energysaving implications when shading devices are applied onglazing with different configurations and thermal perfor-mances. This study provides guidance to facade designerswhen deciding between low performance glazing with shad-ing devices and high performance glazing with or withoutshading devices for possible cooling energy savings. Thisstudy recommends the use of shading devices on low per-formance glazing compared to high performance glazingsince the energy savings are more significant on low perfor-mance glazing. In conclusion, shading devices are moreeffective in achieving cooling energy savings compared tothe use of high performance glazing under the hot-humidclimate in Malaysia. This study recommends further eco-nomic analysis of various types of shading devices andfacade glazing with various thermal performances. Thiswill help facade designers to prioritize between financialaspects and thermal performance of facade materials forhigh-rise office buildings in Malaysia.

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