the effects of orientations on the room's thermal performance in the tropics

8/10/2019 The Effects of Orientations on the Room's Thermal Performance in the Tropics

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The Effects of Orientations on the Room's Thermal Performance in theTropics

Leng Pau Chung1, a, Mohd Hamdan Ahmad2,b Dilshan Remaz Ossen1,c

Malsiah Binti Hamid1,d Mohammad Baharvand1,e 1Department of Architecture, Faculty of Built Environment, Universiti Teknologi Malaysia, Johor

Bahru, Johor Malaysia2Institute Sultan Iskandar of Urban Habitat and Highrise, Level 4, Dewan Sultan Iskandar,

Universiti Teknologi Malaysia, Johor Bahru, Johor Malaysiaa [email protected] ,

b [email protected] ,

c [email protected] ,

[email protected],

e [email protected]

Keywords: orientation, natural ventilation, thermal performance, windows

Abstract. Thermal performance of terrace house in Malaysia very much depends on the spatialdesign due to limited responsive environment factors. Building orientation is one of the important

responsive factors under design consideration. The main concerns of the opening’s orientation are

solar radiation and wind. In Malaysia, the maximum amount of solar radiation directly affects the

thermal performance and thus the orientation of the window should be designed in the way to

minimize solar gain and maximize natural ventilation. This paper investigates the effect of building

orientation on the thermal performance of the residential room with solar chimney. The case study

house facing north was located at Kuching, Sarawak, Malaysia. The field measurement was

conducted in the case study house compound on 16 may 2012 to obtain the boundaries condition for

CFD (Computational Fluid Dynamic) simulation. Four cardinal orientations were selected to

investigate the thermal performance via CFD in DesignBuilder. The results show that the south

facing window could maintain the lowest air temperature in the indoor environment with mean air

temperature of 31.78°C and air mean velocity 0.023m/s with 35°C extreme outdoor temperature and

zero wind velocity.

Introduction. Sustainability becomes the trend of the building industry development over the

concerns of global warming in recent years. As one of the main contributors of the carbon footprint

in global context, building industry has the great responsibility to reduce the emission of the

greenhouse gases [1]. In Malaysia, housing considered as the major contributor of carbon emission

and energy user, which contribute 30% of the total due to the critical dependents of mechanical

ventilation system [2] Thus, rethinking the design for the sustainable residential building with

natural ventilation system is critically important in order to ensure the sustainability no longer amyth. There are dozens of way to go sustainability; however, the best way to achieve sustainability

in housing design is adapting the passive architecture development concept as strategies to improve

the indoor thermal environment and reducing the dependents on mechanical cooling system [3].The

orientation of building is a significant consideration in early design process for architects. Thus, in

this paper the effects of four cardinal orientations on the thermal performance of the residential

room in single storey terrace house that attached with solar chimney were investigated.

Hot and humid climate in Malaysia considered as the most challenges climate to moderate or

handle through architecture design, due to its long hour and high intensity solar radiation throughout

day time, the heavily rains and prevailing winds caused by Monsoon seasons [4]. The terminology

of “passive architecture” can be defined as the ‘ecological building’, ‘green building’, and ‘energyefficient’ building that shield the occupants from local climate elements which form the protective

skin that create thermal comfort to occupants. Thus, from the definition of the passive architecture,

other than huge roof that could protect occupants from direct solar radiation, the orientation of the

Applied Mechanics and Materials Vol. 567 (2014) pp 631-636 Online available since 2014/Jun/06 at www.scientific.net © (2014) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.567.631

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building façade should be one of the considerations in design. According to Zhu and Lin (2004), the

orientation is the passive strategies that should be considered by designer [5]. Other than that,

Thomas and Granham (2007) stated that building orientation is the first action and priority in the

decision making in passive building design [6]. Building orientation in tropical region should be

seriously considered since it has direct effect and interaction with solar radiation and wind direction

[6]. Givoni (1994) supports the fact that the orientation of the building would be influenced by thelocal wind directions which alleviate the effective cross ventilation [7] According to Al-Tamimi et

al. (2011), room located at east orientation has higher temperature compared to west direction

unless with window-wall ratio of 25% both rooms have the similar air temperature [4]. In a study by

Joseph (2003) stated that the north side has the lowest solar intensity from 43.6 W/m² to 65.5W/m²

while west and east sides have similar solar intensity ranged from 86.1 W/m² to 89.6 W/m² [8]. In

this study, the optimum thermal performance of the case study residential room would be studied in

order to obtain the absolute comfortable environment in air temperature and air velocity aspects.

Research Flow & Method

Figure 1: Research flow for the study initated with field measurement and the collected data to be

input as the boundary condition for CFD simulation

In this study, field measurement will be carried out at the case study house compound in

order to obtain the real time weather data for the CFD simulation. The collected data was utilized as

the boundary condition for the CFD simulation for further prediction of the model. The results of

the simulations were compared with the real time outdoor weather data as the benchmark of thermal

performance of the indoor environment.

Figure 2: Location of the case study house Figure 3: The positions of HOBO U30 Weather

station (∆) and location of the case study room (x)

Field Measurement. The field measurement was carried out in a single storey terrace house in

Kuching, Sarawak, Malaysia from 8:00am to 7:00pm of 16 May 2012. The north facing case studyhouse partitioned with two party walls with thickness 230mm and the internal partitions with

thickness 150mm are made up with single brick wall plastered on both side. The external wall with

cement and lime plaster is 200mm and the total U value for the walls is about 0.5 W/m ²K. The

X

∆

632 Structural, Environmental, Coastal and Offshore Engineering



house comprised of 3 bedrooms, a living cum dining space and a utility room. All the windows are

single clear glazed sliding windows (1.5m x 1.2m, and 0.9m above the floor) except bedroom 3

which attached to the solar chimney, which is fitted with glass panes louvers window (1.5m x 1.2m,

0.9 above the floor). The single layer clear glass pane window with U value 1.22 W/m ²K which

installed in case study room (3m x 4m with ceiling height 3m) is facing south and the solar

chimney (0.5m x 2m x 8m height) is attached on the north wall of the room. Clay tiles are selectedfor the roofing material with U value 6.16 W/m²K and no insulation material occupied for both

walls and roofs for heat transmission. In order to obtain the real time weather data, HOBO U30

weather station was set up at the case study house compound. The measured parameters included

solar radiation, wind direction, wind velocity, air temperature and relative humidity. The

measurement only carried out from 8am to 7pm since the study is focus on the effect of the solar

radiation to the solar chimney which incorporated with the orientation of room.

CFD Simulation. The field measurement weather data as shown in Table 1 was input as the

boundary condition for the CFD simulation. The CFD simulation was carried out using

DesignBuilder simulation program. The modeling info is as stated in the section 3.1 for the

construction template The activity set as domestic bedroom and the occupancy set as 0.0229. The

metabolic activity set as bedroom with factor 0.9. The HVAC template set as ‘natural ventilation-

Table 1: Field Measurement Input Data for CFD simulation

Time Air Temperature

[°C]

Humidity

[%]

Wind

Speed[m/s]

Solar

radiation[W/m²]

Wind Direction

[°]

8am 24.2 100 0 31 0

9am 25.6 97 0.03 765 160

10am 26.6 91 0 732 0

11am 31.9 79 0.09 881 120

12pm 31.8 72 0.18 992 140

1pm 32 63 0.1 1000 120

2pm 33.4 63 0.09 760 130

3pm 33.5 44.5 0 852 0

4pm 35 32.3 0 509 05pm 33.2 30 0.02 310 200

6pm 30 89 0 112 0

7pm 30 96 0 25 0

Figure 4: The position of monitoring

points in the case study room.

Monitoring

Point

X (m) Y (m) Z (m)

A 1.712 -3.65 1.3

B 1.712 -2.17 1.3

C 1.712 -0.65 1.3

D 1.712 0.44 1.3

E 1.712 0.44 4.0

F 1.712 0.44 6.5

Table 2: Coordinate of monitoring

point for modeled case study room

Applied Mechanics and Materials Vol. 567 633



no heating or cooling’ and the outside air set as 3 Ac/h. The CFD calculation used the standard K-Ԑ

epsilon turbulent model with 5000 iteration. In this study, only the case study room and solar

chimney will be modeled in order to reduce the complexity of the simulation and time consumed for

simulation. A layer of adiabatic component was modeled means no heat transfer. The simulation

used the Cartesian type-grid system with total number of cell produced is 12 numbers (x-direction)

x 22 numbers (y-direction) x 31 numbers (z-direction). The max aspect ratio is 6.614. Themonitoring points for the CFD slices are listed as in table 2 and figure 4 below. After the CFD

simulation has converged, the CFD slices were exported as csv. file in Microsoft Excel and the air

velocity and air temperature on the specific points were extracted for analysis purpose. In the

simulation, the highest value of the air temperature, which is 35°C with zero wind velocity at 4pm

of 16 May 2012 has been selected in order to find out the thermal performance of the room under

extreme climatic condition.

Designbuilder is reliable software developed by EnergyPlus, which is established by

U.S.DOE building energy simulation program for building simulation, heating and cooling, energy

analysis and so forth [9]. Validation of the software with field measurement has been recognized

and carried out by researchers as a method to verify the simulation software [10-12] DesignBuilderhas been validated by researchers and this software is considered as useful and reliable [12, 13].

Result and Discussions

Field Measurement: Outdoor Climate Condition. Daily climatic patterns in tropical climate

region require effective design strategies to achieve thermal comfort. Understanding of outdoor

climatic condition is important before carrying out simulation. The purpose to carry out the field

measurement is to obtain the real-time condition of the outdoor environment for the input of

simulation. Out of the measured data, the hottest hour was chosen to input as the boundary

condition as only the great temperature differences between indoor and outdoor will promote theventilation rate for indoor room. According to Table 1, the variance range of the air temperature is

24.2°C at 8am to 35°C at 4pm while the relative humidity range from 30% at 5pm to 100% at 8am.

35°C is the maximum air temperature of year 2012 according to Malaysia meteorological

department data. [14] The air temperature is inversely proportional to the humidity. The wind speed

in Malaysia is considered low, where most of the times are 0 m/s and the highest value recorded as

0.18 m/s at 12pm. The peak of the solar radiation value is at 12pm with 1000 W/m ² at 1pm. During

the day time the South-East wind is dominant with less diversity. However the direction of air flows

no longer significant during the evening due to radiation of the land and environment has caused the

air flow direction to divert.

CFD Simulation: Effects of Thermal Performance in Varied Orientation. From the analysis ofthe results from simulation, the air temperature at point A,B,C and D for four cardinal orientations

considered as static. This means that the temperature for the indoor environment is stable. However,

point E and F for four orientations increase drastically due to the stack effect. The heat is moving

upwards and increase. Out of four orientations, East and North facing window have the highest air

temperature for both space, which are test room (point A, B and C) and solar chimney (point D,E,

and F). The East facing window posses the highest temperature in five points (A,B,C,D and E)

compared to other orientation which ranged from 34.65°C to 42.09°C while South facing windows

posses the lowest from 31.77°C to 37.86°C. This fact is supported by Al-Tamimi (2011). [4]. Point

E and F should have higher temperature compared to A, B,C and D due to its function as solar

chimney. The discussion would taken point B as example since it is the habitable zone. With noventilation and extreme outdoor temperature, the differences for in/outdoor temperature for four

orientations were +0.74 (north), +0.36 (east), +3.21 (south) and +0.84 (west). This shows that the

south facing window is the best orientation at May 2012 since it shaded from the evening sun. For




the air velocity stated in figure 6, the east facing window has the greatest differences from point A

to E, which is 86.11% difference. This is caused by the west facing solar chimney absorbed direct

radiation from sun and create the great temperature differences. However, air convection happens in

solar chimney and indirectly increase the room air temperature since both are connected.

In this case, the south facing window posses the ideal condition. The air flow slowly increase

in the room, started from 0.008m/s at point A up to 0.037m/s at point C. Although it is lowcompared to west facing window, with deviation -0.007m/s (point A and C) and -0.09m/s (point B),

the acceptable comfort is still complementary with the lower indoor air temperature. In Figure 7, the

temperature reduction that compared to outdoor temperature occurred at point D, E and F which is

located at solar chimney are ranged from -0.238°C for North facing window, -2.836°C for South

Facing Window, -5.242°C for West window and -7.018°C for East window. The results showing

that the solar chimney is functioning as vertical solar updraft tunnel. The air pressure created by

warm air due to the solar radiation updrafted via solar chimney and replaced by cold air in lower

room via outdoor wind from window. The higher the air temperature differences between point D,

E, F and point A, B, C, the higher the speed of air velocity updrafted via the indoor room. Figure 9

shows that the solar chimney (red colour) has higher air temperature compared to the room (green)and the countour outline showing that the air is updrafted by the solar chimney. The findings show

that the south orientation facing window are most suitable since it could reduce the heat transfer

from glazing and induce buoyancy of the air without influenced by radiation effect.

In addition, according to figure 8, the average air temperature for the outdoor is 30.6°C and

indoor is 30.078°C while the average wind velocity is 0.0425m/s and 0.0219m/s respectively.

Obviously, the outdoor air temperature and air velocity is higher than the indoor environment, with

differences of 1.71% for air temperature and 48.47% for air velocity. This shows that the solar

chimney has the ability to reduce the air temperature and maintain the indoor air speed. The diurnal

air temperature of outdoor environment fluctuated between 24.2°C to 35°C while air velocity

between 0m/s to 0.18m/s. The comparison between outdoor and indoor thermal performance is

important since the trend of air temperature and air velocity in the indoor could be compared withthe outdoor.

30

32

34

36

38

40

42

44

A B C D E F

A i r T e m p e r a t u r e [ ᴼ C ]

Monitoring Points

Air Temperature [ᴼC] of Four Cardinal Orientation

North East South West

Figure 5: Diurnal pattern of air temperaturefor case study model at 16 May 2012.

Figure 6: The diurnal pattern of air velocityfor case study model at 16 May 2012

Figure 7: The temperature reduction of indoor

air temperature compared to outdoor

environment

Figure 8: Comparison of the measured

outdoor and CFD generated indoor average

room air temperature and air velocity.

Applied Mechanics and Materials Vol. 567 635



Figure 9: The air magnitude has been

updrafted shows that stack ventilation

happened in solar chimney.

Conclusion. Appropriate selection of window

orientation could reduce the heat transmission

and thus increase the thermal comfort of

indoor environment. Among the scenarios, the

east window are always hottest compared to

window in other orientations. The southfacing window is the best orientations out of

four since it could maintain the lower air

temperature and induced steady air buoyancy

effect in the indoor environment. In order to

improve the thermal performance, the

selection of glazing with low U value and

shading device to minimize the solar radiation

should be considered. In summary, although

the air flow and air temperature do not

achieve the standard thermal comfortcondition, however, the significant

improvement could enhance the thermal

performance comparable to outdoor

temperature.

Acknowledgment. The authors would like to thank Institute Sultan Iskandar of Urban Habitat &

Highrise for the financial support and assistance from research grant

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Structural, Environmental, Coastal and Offshore Engineering

10.4028/www.scientific.net/AMM.567

The Effects of Orientations on the Room's Thermal Performance in the Tropics

10.4028/www.scientific.net/AMM.567.631

DOI References

[1] Z.M. Gill, M.J. Tierney, I.M. Pegg, N. Allan. Measured energy and water performance of an aspiring low

energy/ carbon affordable housing site in the UK. Energy and Buildings. 2011; 43(1): 117-25.

http://dx.doi.org/10.1016/j.enbuild.2010.08.025

[3] A.M. Abdul Rahman, N.S.A. Rahim, K. Al-Obaidi, M. Ismail, L.Y. Mui. Rethinking the Malaysian

Affordable Housing Design typology in View of Global Warming Considerations. Journal of Sustainable

Development. 2013; 6(7): 134-46.

http://dx.doi.org/10.5539/jsd.v6n7p134

[5] Y.X. Zhu, B.R. Lin. Sustainable housing and urban construction in China. Energy and Buildings. 2004;

36(12): 1287-97.


[8] J.C. Lam, D.H.W. Li. An analysis of daylighting and solar heat for cooling-dominated office buildings.

Solar Energy. 1999; 65(4): 251-62.

http://dx.doi.org/10.1016/S0038-092X(98)00136-4

[10] M.Z.I. Bangalee, J.J. Miau, S.Y. Lin. Computational techniques and a numerical study of a

buoyancydriven ventilation system. International Journal of Heat and Mass Transfer. 2013; 65(0): 572-83.

http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.06.040

[11] G. Evola, V. Popov. Computational analysis of wind driven natural ventilation in buildings. Energy and

Buildings. 2006; 38(5): 491-501.


http://dx.doi.org/www.scientific.net/AMM.567

http://dx.doi.org/www.scientific.net/AMM.567.631

http://dx.doi.org/http://dx.doi.org/10.1016/j.enbuild.2010.08.025

http://dx.doi.org/http://dx.doi.org/10.5539/jsd.v6n7p134


http://dx.doi.org/http://dx.doi.org/10.1016/S0038-092X(98)00136-4

http://dx.doi.org/http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.06.040



http://dx.doi.org/http://dx.doi.org/10.1016/j.ijheatmasstransfer.2013.06.040

http://dx.doi.org/http://dx.doi.org/10.1016/S0038-092X(98)00136-4


http://dx.doi.org/http://dx.doi.org/10.5539/jsd.v6n7p134


http://dx.doi.org/www.scientific.net/AMM.567.631

http://dx.doi.org/www.scientific.net/AMM.567

the effects of orientations on the room's thermal performance in the tropics

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