Thermal comfort, temperature and humidity variation according to Malaysian terrace house orientation

Sivaraman s/o Kuppusamy Faculty of Architecture and the Built Environment, Limkokwing University of Creative Technology, Cyberjaya, Malaysia

Abstract: Cross-sectional study was carried out with specific objective to determine the mean indoor temperature, outdoor temperature, relative humidity and indoor thermal comfort level in relation to north-south orientated and east-west orientated of single storey terrace houses. The study focused on 32 units of north-south orientated and 32 units of east-west orientated single storey terrace houses in Petaling Jaya, Selangor Darul Ehsan, Malaysia The instrument used is Thermo-Hygrometer, Model: THG312 which monitors the indoor temperature, outdoor temperature and relative humidity digitally at 3 hours intervals form 10.00 pm to 7.00 pm on 2 consecutive days. T-test revealed that the mean indoor temperature is proportionate to mean outdoor temperature but the mean relative humidity is reciprocal to mean outdoor temperature. Using Multiple Linear Regression – ‘Stepwise’ method, a Mathematical Models showing different influence on different time period were developed for both north-south and east-west orientated single storey terrace houses. R2 which indicates the relationship strength and p-value which indicates the significance revealed that the east-west orientated single storey terrace houses have stronger correlation / association of the mean outdoor temperature and the mean relative humidity on the mean indoor temperature.

Conference Theme: Effective environments: thermal, luminous, sonic, haptic, hygienic. Keywords: Thermal comfort, Orientation, Indoor temperature, Outdoor temperature, Relative humidity.

1.0 INTRODUCTION

Thermal comfort for a person is defined as “that condition of mind, which expresses satisfaction with the thermal environment” (Fanger, 1970). If a population is considered a state of “thermal comfort” exists when a percentage of those persons exposed to a given environment who indicate that it is “acceptable” (Gagge, 1981). The percentage “acceptable” is 80% in the ASHRAE (American Society of Heating, Refrigeration and Air Conditioning Engineers) standard and 95% in the comfort formula used by Fanger (1970). Creating a thermally comfortable environment is still one of the most important parameters to be considered when designing buildings (Innova, 1997). To build a thermally comfortable housing environment, it should be made at the design stage itself (McIntyre, 1981). Straaten J.F. Van (1967) suggested that there are three (3) requirements to be considered in the thermal design of building. First the evaluation of indoor environment factors, second, outdoor environment factors and finally the design of the building itself.

During the day, Malaysian concrete houses absorb the solar radiation through the roof and walls and the heat is stored in the concrete mass increases the indoor temperature of the house, 2oC to 5oC hotter than outdoor temperature. When the sun goes down, the walls reradiates the stored heat and turns house into an oven whereby the indoor temperature is above the upper thermal comfort level (28oC for Malaysian humid tropics) for much of the night, particularly after hot days. (Davis, Shanmugavelu, Adam, 1997). In the study carried out by Davis et al (1997), the results shows that single storey and double storey link houses are only thermally comfortable (defined by these authors as being between 24 oC to 28 oC) for a brief of 3 to 5 hours in the early morning. Overheating and thermal discomfort in concrete/brick houses has been a source of problem and a fundamental defect for a long time in modern Malaysian houses (Davies and Shanmugavelu, 1999). It is common to find that 40-60% of the home's heating and cooling costs could be saved with proper but simple planning with a little extra cost (IRPA,1998).

Increased use of air-conditioning releases substantial amounts of heated carbon dioxide and chlorofluorocarbons into the atmosphere, further affecting our already polluted air quality. The situation is urgent as there are 2.4 million such houses (A.M.A. Rahman, 1995). Air conditioners are very wasteful and expensive solution which does not address the underlying problem. Furthermore it can cost more in electricity to run the air conditioner over 40 years than the original cost of the house (Davis et al., 1997). Climate-sensible design in Malaysia should be carried out with more thought for internal comfort. “Sick Buildings Syndrome” is a term applied to modern buildings when occupants experience discomfort that may have arisen from poor design of the building. They may reflect a failure in the ability of a building to provide a satisfactorily comfortable environment for the occupants to work in (Chow et al, 1991). The potential factors causing this syndrome include extremes of thermal comfort, reduced humidity, insufficient fresh air supply, and excessive air movement (Occupational and Environmental Medicine Journal, 2000; 57). Research into causal factors of the sick building syndrome have examined a variety of sources such as air-conditioning, low ventilation rates, low air velocity, high temperature and low relative humidity (Scandinavian Journal Work Environmental Health, 1996; 22).

41st Annual Conference of the Architectural Science Association ANZAScA 2007 at Deakin University 142 In a random household survey carried out by a well known university, University Putra Malaysia, 50-75% says that their terrace houses are too hot on half the days of the year. It is termed the ‘sweat box effect’. The experiments prove that 10 million Malaysians living in 2 million overheated concrete houses would suffer 2-3 times less “heat stress” if they abandoned their houses and lived under trees. On hot days inside their houses, some 67% say they suffer headaches, one third reported getting angry and one third reported getting dizzy or sick which are general symptoms of “heat stress”. Death from heatstroke can occur at 39oC under Malaysian humidity in perhaps 20 minutes (Bulletin Ingenieur,2002; 2). “Heat stress” is the integrated net thermal load on the body that is imposed by environmental temperature, humidity, wind speed, metabolic work demands and clothing (AIHA Journal, 2003; 64). With high “heat stress” levels, mental confusion can develop and other heat illness can occur such as heat syncope, heat exhaustion, heat cramps, classic and exert ional heatstroke (Occupational Medicine, 2001;51).

2.0 THERMAL COMFORT

Dung (1995) defined ‘human thermal comfort’ as the background for setting up and improving of the standards of the indoor air temperature in the housing, public and industrial buildings. There is no “ideal temperature” for any group of people or individuals as it vary greatly in physical characteristics, temperaments and adaptability (Angus, 1968). The function of discomfort is to protect the person from extreme conditions. For example, a range of a few degrees of temperature is comfortable for most people, which called “thermal comfort” range. Extend the temperature out of this range, people will become increasingly more “thermally uncomfortable” (Bennet, 1977).

Climate (from Greek: klima) is defined by the Oxford dictionary as ‘region with certain conditions of temperature, dryness, wind, light, etc.’ A more scientific definition is: ‘an integration in time of the physical states of the atmospheric environment, characteristic of a certain geographical location.’ ‘Tropical climates’ like Malaysia are those where heat is the dominant problem, where, for the greater part of the year buildings serve to keep the occupants cool, rather than warm, where the annual mean temperature is not less than 20 0C (Koenigsberger et al, 1973). Micro-climatic data is required for the formulation of the building type, orientation and form given for desired function. It is also pertinent to the assessment of thermal comfort of the occupants. Micro-climatic data required are such as longitude and latitude, air temperature, relative humidity, rainfall, wind velocity and solar radiation.

In order to evaluate thermal sensation and its significance in respect of human comfort and efficiency, there are six important variables to be considered. It is air temperature, relative humidity, air velocity / air movement, mean radiant temperature (MRT), activity level and clothing (Angus, 1968; Bennet, 1977; Cena and Clark, 1986; Fanger, 1970; Goromosov, 1968; Jennings, 1978; Kukreja, 1978; McQuiston and Parker, 1988). This six important factors influence each other in some way the heat exchange process between the human body and its environment (Koenigsberger et al, 1973). To create thermal comfort, we must understand not only the heat dissipation mechanisms of the human body but also the air temperature, relative humidity, air velocity and the mean radiant temperature (Lechner, 2001). The indoor thermal environment of house is influenced by the thermal characteristics of exterior envelope (Li, 1992). To maintain a suitable internal “thermally comfortable” environment, there are several factors can be controlled in designing of a building such as orientation, building materials, ventilation / air movement, insulation, shading devices and landscaping (Senn, 1964).

3.0 RESEARCH METHODOLOGY

The study area focused on sixty four (64) units of single storey terrace houses constructed of bricks and concrete in Petaling Jaya, Selangor Darul Ehsan, Malaysia. The selected single storey terrace houses for the study will be of two (2) categories. Category one (1), thirty-two (32) units of North-South orientated single storey terrace houses, in reference to the front or rear of the houses is facing either North or South with 20o angle adjustment on east or west side and category two (2), thirty-two (32) units of East-West orientated single storey terrace houses, in reference to the front or rear of the houses is facing either East or West with 20o angle adjustment on north or south side (refer to the layout and the picture below).

2 41st Annual Conference of the Architectural Science Association ANZAScA 2007 at Deakin University 143 This study is a cross-sectional and intended to determine whether the orientation of single storey terraced houses (north-south and east-west) have any relation to the cause of thermal discomfort to the occupants. This study also determines whether there is any influence of mean outdoor temperature and mean relative humidity on mean indoor thermal comfort level. Primary data of north-south orientated and east-west orientated single storey terrace houses mean indoor temperature, mean outdoor temperature and mean relative humidity will be obtained and analyzed. Data was collected for 2 days from 10 pm to 7 pm continuously and the mean was found for both the orientation separately and analyzed.

The instrument used is Thermo-Hygrometer, Model: THG312 (refer the picture below). This rectangular device monitors the indoor temperature, outdoor temperature and relative humidity digitally. To read the outdoor temperature and the relative humidity, it has a connector wire with a receptor rod acts like a probe at the end of the wire.

4.0 RESULTS AND DISCUSSION

The table 4.0 below shows the summary of relationship between the mean indoor temperature, the mean outdoor temperature and the mean relative humidity for north-south and east-west orientated single storey terrace houses.

For north-south orientated single storey terrace house, at 10 pm, 4 am and 1 pm there is no significant influence of the mean outdoor temperature and the mean relative humidity on the mean indoor temperature. It can be concluded that, at these particular time for north-south orientation, the mean outdoor temperature and the mean relative humidity do not significantly influence the mean indoor temperature. At 1 am and 7 pm, only the mean outdoor temperature have significant influence on the mean indoor temperature. Where else, at 7 am and 4 pm, only the mean relative humidity have significant influence on the mean indoor temperature. At 10 am, both the mean outdoor temperature and the mean relative humidity have significant influence on the mean indoor temperature.

41st Annual Conference of the Architectural Science Association ANZAScA 2007 at Deakin University 144 TABLE 4.0 Summary of Relationship between Mean Indoor Temperature with Mean Outdoor Temperature and Mean Relative Humidity for North-South and East-West Orientated Single Storey Terrace Houses

Outdoor Relative Model For Time Constant Temperature Humidity Indoor Temperature (OT) (RH) (IT)

10 pm No relationship between Indoor, Outdoor and Relative Humidity

1 am 18.573 0.380 IT = 18.573 + 0.380 (OT)

4 am No relationship between Indoor, Outdoor and Relative Humidity

7 am 36.954 - 0.111 IT = 36.954 – 0.111 (RH)

10 am 34.370 0.120 - 0.118 IT = 34.370 + 0.120 (OT) – 0.118 (RH) Orientation North-South 1 pm No relationship between Indoor, Outdoor and Relative Humidity

4 pm 40.992 - 0.142 IT = 40.992 – 0.142 (RH)

7 pm 23.444 0.224 IT = 23.444 + 0.224 (OT)

10 pm 22.422 0.479 - 0.074 IT = 22.422 + 0.479 (OT) – 0.074 (RH)

1am 30.712 0.671 - 0.248 IT = 30.712 + 0.671 (OT) – 0.248 (RH)

4 am 26.657 0.576 - 0.167 IT = 26.657 + 0.576 (OT) – 0.167 (RH)

7 am 34.907 0.889 - 0.358 IT = 34.907 + 0.889 (OT) – 0.358 (RH)

10 am No relationship between Indoor, Outdoor and Relative Humidity East-West Orientation 1 pm 53.766 - 0.224 - 0.220 IT = 53.766 – 0.224 (OT) – 0.220 (RH)

4 pm 149.623 - 3.045 - 0.323 IT = 149.623 – 3.045 (OT) – 0.323 (RH)

7 pm 41.736 0.412 - 0.312 IT = 41.736 + 0.412 (OT) – 0.312 (RH) * The mean difference is significant at the p < 0.05 level

For north-south and east-west orientated single storey terrace house, the correlation between the mean indoor temperature, the mean outdoor temperature and the mean relative humidity is irregular. Therefore a separate model is developed to show the different relationship at different time period. Furthermore for north-south orientated single storey terrace house, the model indicates that the mean outdoor temperature have proportionate influence over the mean indoor temperature, but the mean relative humidity have reciprocal influence over the mean indoor temperature.

Where else, for east-west orientated single storey terrace house, only at 10 am there is no significant influence of the mean outdoor temperature and the mean relative humidity on the mean indoor temperature. It can be concluded that, at these particular time for east-west orientation, the mean outdoor temperature and the mean relative humidity do not significantly influence the mean indoor temperature. At 10 pm, 1 am, 4 am, 7 am and 7 pm, the mean outdoor temperature and the mean relative humidity have significant influence on the mean indoor temperature. From the model it indicates that the mean outdoor temperature have proportionate influence over the mean indoor temperature, but the mean relative humidity have reciprocal influence over the mean indoor temperature. At 1 pm and 4 pm, the mean outdoor temperature and the mean relative humidity also have significant influence on the mean indoor temperature but from the model it indicates that the mean outdoor temperature and the mean relative humidity both have reciprocal influence over the mean indoor temperature.

4 41st Annual Conference of the Architectural Science Association ANZAScA 2007 at Deakin University 145 Table 4.1 below shows the summary of relationship of (R2) and (p-value) between the mean indoor temperature, the mean outdoor temperature and the mean relative humidity for north-south and east-west orientated single storey terrace houses.

TABLE 4.1 Summary Of Relationship Showing (R2) and (p-value) Between Mean Indoor Temperature with Mean Outdoor Temperature and Mean Relative Humidity for North-South and East-West Orientated Single Storey Terrace Houses.

Model For Indoor Temperature 2 Time R p (IT)

10 pm

1 am IT = 18.573 + 0.380 (OT) 24.5 % 0.004

4 am

7 am IT = 36.954 – 0.111 (RH) 30.4 % 0.001

10 am IT = 34.370 + 0.120 (OT) – 0.118 (RH) 67.1 % < 0.001 Orientation North-South 1 pm

4 pm IT = 40.992 – 0.142 (RH) 31.4 % 0.001

7 pm IT = 23.444 + 0.224 (OT) 23.0 % 0.006

10 pm IT = 22.422 + 0.479 (OT) – 0.074 (RH) 74.1 % < 0.001

1 am IT = 30.712 + 0.671 (OT) – 0.248 (RH) 66.3 % < 0.001

4 am IT = 26.657 + 0.576 (OT) – 0.167 (RH) 75.4 % < 0.001

7 am IT = 34.907 + 0.889 (OT) – 0.358 (RH) 91.1 % < 0.001

10 am East-West Orientation 1pm IT = 53.766 – 0.224 (OT) – 0.220 (RH) 81.3 % < 0.001

4 pm IT = 149.623 – 3.045 (OT) – 0.323 (RH) 75.0 % < 0.001

7 pm IT = 41.736 + 0.412 (OT) – 0.312 (RH) 91.2 % < 0.001

* The mean difference is significant at the p < 0.05 level

For the north-south orientated single storey terrace house, the strength of relationship (R2) of the mean outdoor temperature and the mean relative humidity on the mean indoor temperature ranges from 23 % to 67.1 % and the significance (p-value) ranges from < 0.001 to 0.006. For the east-west orientated single storey terrace house, the strength of relationship (R2) of the mean outdoor temperature and the mean relative humidity on the mean indoor temperature ranges from 66.3 % to 91.2 % and all the significance (p-value) is < 0.001. Comparatively, the strength of relationship (R2) for east-west orientated single storey terrace house indicates a higher % compared to north-south orientated single storey terrace house. Furthermore, the east-west orientated single storey terrace house indicates a p-value of < 0.001 which is highly significant compared to north-south orientated single storey terrace house, even though the mean difference is significance at the p < 0.05 level.

5.0 CONCLUSION AND RECOMMENDATIONS

5.1 Conclusion

There is a correlation / association between the mean indoor temperature, the mean outdoor temperature and the mean relative humidity of north-south and east-west orientated single storey terrace house. Analysis from the summary of relationship showing R2 and the p-value (Table 4.1) indicates that comparatively, east-west orientated single storey terrace houses have stronger correlation / association between the mean indoor temperature, the mean outdoor temperature and the mean relative humidity. It also can be concluded that there is a correlation / association between the indoor thermal comfort level of north-south orientated and east west orientated single storey terrace houses. Analysis also indicates that comparatively, indoor thermal comfort level of east-west orientated single storey terrace houses have stronger correlation / association.

41st Annual Conference of the Architectural Science Association ANZAScA 2007 at Deakin University 146 The sample site, Petaling Jaya is located at Latitude 3q 6’ N whereby most of the heat gain through the solar radiation in a building is received through the east wall, south wall and west wall. This is due to the sun path (movement) which is through EastÙSouthÙWest side.

This sun path (movement) also explains why there is a strong correlation / association between the mean indoor temperature, the mean outdoor temperature and the mean relative humidity towards east-west orientated single storey terrace houses which also indicates on why there is a strong correlation / association on the indoor thermal comfort level on east-west orientation. For north-south orientated single storey terrace house, the strength of relationship (R2) is on the lower end or weak ranging from 23 % to 67.1 % due to other factors which influences the mean indoor temperature ranging from 32.9 % to 77 %. Similarly, for east-west orientated single storey terrace house, the strength of relationship (R2) is on the higher end or strong ranging from 66.3 % to 91.2 % due to other factors which influences the mean indoor temperature ranging from 8.8 % to 33.7 %. These factors are such as the colour of external wall paint and roof tiles whereby darker colour have higher absorption coefficient of heat, heat emitted from human body due to different metabolic activities, heat emitted from equipment e.g. lights, computers and the rate of ‘heat flow’ emitted from human or equipment used in the houses whereby ‘heat flow’ is the heat being conducted to colder objects.

5.2 Recommendations

This study has concluded that there is a statistically significant relationship between the mean indoor temperature, the mean outdoor temperature and the mean relative humidity of the east-west orientated single storey terrace houses, arrangement of the floor plan for thermal planning can be carried out for both present and future development planning of houses. A solar / thermal bubble diagram for designing a residence can be carried out for future development planning of houses. Bedrooms and utility areas can be placed at north orientation to create cool spaces, kitchen and dining areas can be placed at east orientation to create morning spaces, family and living areas can be placed at south orientation for warm spaces and garage / store rooms can be placed at west orientation to create hot spaces. Environmentally we are under stress due to issues like green house effects, global warming and rise of sea level due to increase in global temperature makes us to re-look into our current practices. One small positive step a head will make up our homes a better place to live.

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