Investigations on effect of the orientation on thermal comfort in terraced housing in Malaysia

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1 Investigations on effect of the orientation on thermal comfort in terraced housing in Malaysia Dr Mohamed Ali Abdul Hussain Al-Obaidi 1 and Prof. Peter Woods 2 1 Senior lecturer, Center for Equatorial Sustainable Design, Faculty of Built Environment, University of Malaya, 563 Kuala Lumpur, Malaysia m_ali_architect@hotmail.com 2 Professor, Faculty of Creative Multimedia, Multimedia University, 6 Cyberjaya, Selangor, Malaysia p.woods@mmu.edu.my Abstract The design of residential buildings has a significant impact on people s daily life. The terrace house form constitutes the majority of the residential building stock in Malaysia. The lack of thermal comfort in terrace houses is mainly due to the poor thermal properties of the building materials and to design factors [1]. The evaluation is derived from a series of computer simulations using commercially available software. This paper concentrates on analysing the effect of the orientation of the existing case of a typical terrace house in Malaysia by finding the dynamic indoor air temperature for each orientation. 1. Introduction This paper aims to study the dynamic factors of temperature variations (hourly) under the effect of different orientations (north, northeast, east, southeast, south, southwest, west and northwest). The climatic parameters in Malaysia (KL) are analysed over a thirty-year weather data period in order to find the typical Design Day. This data is vital to the calculation. The climate in Malaysia can generally be described as tolerable in terms of thermal requirements. The common prototype design has been chosen in this study to represent the terrace house in Malaysia. A series of computer simulations using commercially available software known as the BLAST is conducted to evaluate the dynamic indoor air temperature within 24 hours. 2. Research aim and objectives The aim of this paper is to study and explain the effect of the orientation as a design variable in reducing the indoor air temperature, which is important to the designer and researcher. This will be valuable to designers in evaluating the thermal comfort significance for design decisions in architecture. 3. Orientation The amount of solar radiation received by the building envelope depends on its orientation. An important clue in developing energy efficient facades is knowledge

2 168 M. Ali. Al-Obaidi and P. Woods Stereographic Diagram Location: 3.1, N st Jun 285 1st May 1st Apr 27 1st Mar 1st 255 Feb 1st Jan Figure about the distribution of solar radiation due to orientation. Buildings should be planned in such a way that benefit is obtained from shaded indoor and outdoor living areas when the weather is hot. The high angle of the sun makes it easy to shade the house by a generous roof overhang. This is because the sun is much lower in the sky throughout the day, favoring the vertical surface (Fig. 1). The incident radiation on the east face in the morning and the west face in the evening is still high, but not as high as that on the north face during the middle of the day. The south face receives no direct component [2] Because in hot-humid regions close to the equator the diffuse radiation has a predominant share of the overall radiation and the fact that the distribution of the diffuse radiation is almost identical at all orientations, the orientation of the buildings might be more influenced by other external aspects, like the prevailing wind direction. [3]. Table 1 shows the orientations that are used in the analysis of this study. 4. Thermal comfort studies in Malaysia For comparison purposes, the results of the criteria from several sources are summarized in Table 2. For example, the temperature range obtained from Zain [4] is between deg C, which is lower than Abdulmalik [5] but higher than the range suggested by the Ministry of Energy, Telecoms and Posts. This table comprises eight thermal comfort studies, four of which have been carried out on Malaysians either in climate chambers or as field studies. The outcomes of the studies differ slightly due to different test procedures. However, most of the studies seem to agree on a Malaysian comfort temperature of around 25 deg C air temperature. 6 1st Jun st May 1st Apr 9 1st Mar 1st 5 Feb 1st Jan F J 27 M M A J Left: The sun path behind the wall in January north orientation. Right: The sun path in different orbit in the year [7] D 14 3 N N 12 O S J A

3 Investigations on effect of the orientation on thermal comfort in terraced housing in Malaysia 169 Table 1. Explanatory table for all the orientations that used in this study, Source: Ali. [7] Angle Angle Direction degree Direction Degree North South 18 North-East 45 South-west 225 East 9 West 27 South-East 1 North-West 5 Table 2. Thermal comfort studies in Malaysia, Source: Ali. [7] Air Range Comfort Zone Humidity Velocity Study ( C) ( C) Type of Study range (%) (m/s) FANGER Climate Chamber 8.1 Zain Ahmed Field Study Abdulmalik Climate Chamber 45 9 Davis Field Study Ministry of Energy, Field Study Telecom and Posts, Malaysia Brooks Field Study ASHRAE Climate Chamber Abdul Rahman Climate Chamber Simulation programs and BLAST program Selecting the BLAST program (Building Loads Analysis and System Thermodynamics), for which seemed suitable the aims and methodology of the research. BLAST is a family of programs for predicting heating and cooling energy consumption in buildings and analyzing energy costs. HBLC (Heat Balance Loads Calculator) is an easy-to-use graphical user interface for the BLAST engine. Together BLAST and HBLC form a comprehensive thermal software package. Evans [9]. Supporting computer programs have been developed to facilitate weather file generation, automated simulation process, the extraction of key results and data analysis on microcomputers. 6. Building model: the typical Malaysian terrace house The common prototype design has been chosen in this study to represent the terrace house in Malaysia. Thirty-seven layouts of terrace houses constructed in Malaysia were obtained from architectural firms in Kuala Lumpur. From these plans, a typical terrace house was derived incorporating the most commonly occurring layouts and

4 17 M. Ali. Al-Obaidi and P. Woods Figure 2. Left: The prototype space in the terrace house. Right: Plan of the Terrace house for simulation studies. space types and sizes. This typical terrace house is shown in figure1, which shows a two storied terrace house where each floor is divided into 4 or 5 spaces for the average Malaysian family of 5 persons living in terrace house. The terrace house consists of the ground floor, with spaces for living/dining area, kitchen, bedroom, bathroom and staircase and the first floor, with spaces for master bedroom (bathroom en suite), bedroom, child bedroom, bathroom and staircase (Ali) [7] Fig Kuala lumpur climate The climatic parameters in Malaysia (KL) are analyzed over a thirty year weather data in order to find the typical Design Day, This data is vital to the calculation. The climate of Malaysia can generally be described as tolerable in terms of thermal requirements. Diurnal temperature variations are small due to the presence of clouds throughout the day. Cloud cover also occurs at night causing warmer nights. Heat trapped between the ground and cloud may cause the air temperature to rise due to re-radiation from the ground at night, especially when the wind speed is low and humidity is high. The daily climatic data indicates that the temperature rises as high as deg C at hours when the global radiation is at its highest. Humidity of 67% RH is the lowest in the region and the average is more than 8%. In spite of the fact that the wind has no dominated direction, its presence over most of the day helps to maintain comfort conditions inside buildings. (Ali) [7] Fig. 3, Table The analysis of hourly indoor air temperature in the living & dining room Figure 4 shows that the best orientation of the living room in January is northward and in June is southward because both recorded a minimum indoor air temperature

5 Investigations on effect of the orientation on thermal comfort in terraced housing in Malaysia 171 Table 3. Records of monthly mean of temperature, humidity & wind speed for the last 29 years, Source: Ali. [7] Number of the years JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC Annual TEMP. MEAN years MEAN OF MAX. years MEAN OF MIN. years Relative Humidity (RH) years The Mean of Wind years Speed (m/s)

6 172 M. Ali. Al-Obaidi and P. Woods RELATIVE HUMIDITY RELATIVE HUMIDITY RELATIVE HUMIDITY TEMPERATURE THE HOURS THE DAYS Figure 3. RELATIVE HUMIDITY TEMPERATURE with a peak value of.2 deg C. At the same time Figure 4 shows that the worse orientations in January are southeast and southwest because both recorded a maximum, mean indoor air temperature with a peak value of about.5 deg C. Meanwhile, in June the northwest and northeast-recorded maximum mean indoor air temperatures with a peak value of.4 deg C. Figure 4A shows that the maximum mean variation among the indoor air temperature mean value in January ranges between 29.8 deg C and.7 deg C and in June between.3 deg C and.4 deg C as in Figure 4B TEMPERATURE deg C TEMPERATURE deg C Local Time Solar Time Altitude January Altitude July 7: 6: 14.1 o 3.5 o 7: 6: 21.1 o.6 o 8: 7: 28 o 17.6 o 8: 7:.9 o 24.7 o 9: 8: 41.6 o.7 o 9: 8: 48 o.7 o : 9: 54.1 o 45.6 o : 9: 59.7 o 52.3 o 11: : 64.3 o 58.8 o 11: : 67.4 o 64.8 o 12: 11: 68.3 o 69.8 o 12: 11: 66.7 o 73.2 o 13: 12: 63.2 o 73.7 o 13: 12: 58.3 o 71.1 o 14: 13: 52.6 o 66.4 o 14: 13: 46.3 o 6.7 o 15: 14:.8 o 54.3 o 15: 14:.1 o 47.7 o 16: 15: 26.2 o.8 o 16: 15: 19.3 o.9 o 17: 16: 12.4 o 26.9 o The records of hourly and monthly mean of temperature, humidity, altitude sun angle and solar radiation for Kuala Lumpur climate, Source: Ali [7].

7 Investigations on effect of the orientation on thermal comfort in terraced housing in Malaysia 173 January: The Living & Dining in ground Floor June: The Living & Dining in ground Floor Living & Dining- JAN. Space (1) Hours MAX. occupancy hours TEMPERATURE Mean of 24 Hours MIN Living Orientation temperature Oreintation avarag e24 hours Time for Min&Max TEMPERATURE Oreintation Time Space Time (1) Mean of 24 Hours MIN MAX occupancy hours (A) (B) Living& Dining Room in Ground floor - 8 Orientation January (C) Hourly Mean temp January min max HOURS am. (min. pm temp) (max. temp.) Living & Dining -June Living & Dining Room in Ground floor - 8 Orientation June June min max HOURS am. (Min. temp) pm (Max. temp.) north :9: 6. north northeast :8. northeast : 8. 3.:4: east : east :7. 4. southeast :4. southeast :7. 6. south south : southwest southwest west :. 6. west northwest : northwest : (E) (F) Hours Living Orientation temperature avarag e24 hours (D) Time for Min&Max Hourly Mean temp. Figure 4. A and B: The hourly temperature of the living and dining room in January and June. C and D: The hourly temperature Curves through eight orientations in January and June. E and F: The hourly peak values within occupancy hours in January and June.

8 174 M. Ali. Al-Obaidi and P. Woods Moreover, as seen in Fig. 4 for all orientations, it is observed that in both January and June, for 24 hours the hourly minimum indoor air temperature occurs in the morning from 6. am to 8. am, except northwestward and northward where the minimum indoor air temperature continues until 11. am. The hourly maximum indoor air temperature usually occurs at 6. pm while with eastward it occurs from 3. pm to 4. pm. Peak hours occur from 2. to 4. pm with east and southeast orientations. Figures 4 indicate that the indoor air temperature variation within one year is not more than 7 deg C since the minimum indoor air temperature value is 29.8 deg C and the maximum indoor air temperature value is.7 deg C. However, the variations of means of indoor air temperatures among all orientations throughout a year are less than that because the minimum mean value is.5 deg C and, the maximum is.deg C so the difference between them is less than 3.5degC. N NE45 E 9 SE1 S 18 SW225 W 27 NW 5 (Ceiling Heights)-North ONE YEAR GROUND FLOOR FIRST FLOOR Activity (Ceiling Heights)-NorthEast 45 Oreintation (Ceiling Heights)-East The Living & Dining Kitchen Bath The Stair Bed Room Master bath nd Bed Room nd Bath Child Bed Room Corridor In 1st Master Bed Room Mean of 24 Hours Activity Mean (Ceiling Heights)-SouthEast 1 The mean of temperature (Ceiling Heights)-South 18 (Ceiling Heights)-South West 225 (Ceiling Heights)- West All the Spaces against the mean temperature for 8 orientations in One YEAR The Living & Dining Kitchen 1 Bath The Stair 1Bed Room Master bath 2nd Bed Room 2nd Bath Child Bed Room Corridor In 1st Master Bed Room (Ceiling Heights)-NorthWest The Orientation (angle -degree) C) ONE YEAR C) ONE YEAR Figure 5. Top) Hourly temperature for different orientations for the living room. Left) Table of the hourly mean indoor air temp. Value for all the spaces due to eight directions. Right) Curves mean of indoors air temperature to eight directions in one year.

9 Investigations on effect of the orientation on thermal comfort in terraced housing in Malaysia The mean of indoor air temperature values through one year The highest indoor temperature values are towards eastward, westward and the lowest are northward and southward, Figure 5 right curves. It is interesting to note that the sequential arrangement of the mean temperature values, from the lowest to highest for the terrace house spaces throughout the year, is quite similar to that of January while it is slightly different from June observed only with bathrooms and first bedroom.. Conclusions and recommendations The main points for the existing terrace house Orientation analysis can be summarized as follows: First, it has been found that the effect of orientation is one of the most important design variables upon the indoor temperature with a value of partial correlation equal to 58%. Second, the orientation of the exposed walls of the terrace house should be on the North South axis, i.e. facing North and South in order to minimize solar heat gain. The best orientations for all spaces, as a general rule, are Southward and northward. This is because both orientations have recorded the same minimum mean temperature throughout the year, with a peak value of about.2 deg C because of the Sun s position in these directions (no direct radiation). The worst orientations Figure 6. The best orientation for the terrace house in Malaysia.

10 176 M. Ali. Al-Obaidi and P. Woods are Westward and Eastward both of which have recorded maximum internal mean temperatures throughout the year compared to other orientations with a peak value of.4 deg C. (Appendix A). Therefore, it will be useful to arrange the front and back façades of a terrace house to the North and South while there is no effect to the bad orientations East and West because these sides are attached already to the other adjacent houses as in Fig. 6. Third, the effect of orientation on the indoor air temperature of the façade spaces is very high; it may reach up to 4 deg C during the night hours, increasing to 7 deg C during the day. Forth, all the temperature curves for June are mirror images of the January temperature curves (Figures 5 and 6). Therefore, the temperature curve for the North Front elevation in January has the same shape as the curve for the South Back elevation in June. Since the terrace house has only two elevations (front and back) it becomes difficult to provide the best orientation for both of them at the same time. North at ( degree) = South at (18 ) West at (27 ) = East at (9 ) Southeast at (1 ) = Northeast at (45 ) Southwest at (225 ) = Northwest (5 ) Fifth, it is necessary to avoid windows on the eastern and especially the western face of the terrace house as these locations are particularly difficult to shade. The east and west facing surfaces receive the most sun in the mid-morning and mid afternoon respectively. Western surfaces are especially difficult to shade; therefore, window areas on these surfaces should be minimized. The preferred orientation of windows should follow the same pattern, with the main windows facing north and south. The north façade is better as it is easier to shade. References [1] Koenigsberger, Ingersoll, Mayhew, Szokoloy. Manual of tropical housing and building, part 1, climatic design. London and New York: Longman Group, LTD., (1978). [2] B. Givoni, Man climate and architecture, 2nd addition, London: Applied Science Publishers LTD, (1976) [3] B. C. Raychaudhuri, S. Ali and D. P. Garg, Indoor climate of residential buildings in hot arid regionseffect of orientation, Building science 1, no.1, (1965). [4] A. Zain Ahmed, Model Year Climate for Klang Valley, Malaysia, Seminar on Advances in Malaysia Energy Research, (1998), [5] A. Abdulmalik and A. Young, Thermal comfort study as an aid to determine energy savings in building in Malaysia, Proc. Energex 93, Vol.II, Seoul, (1993). [6] P. C. Woods, Mohammed Ali and Lukman, Design Model Day Climate in Malaysia. Seminar in Architectural Department, University Malaya, November, (2). [7] Ali, Mohamed, Dynamic thermal performance of construction materials in the design of a terrace house in the Klang Valley, Malaysia for satisfactory thermal comfort, Ph.D Thesis, Faculty Built Environment, University of Malaya, Malaysia, (24). [8] Malaysian Meteorological Station Service, Climatologically Section, Jalan Sultan, 462 Petaling Jaya, Klang Valley, Selangor, Malaysia, (2). [9] R. Evans, Guidelines for the selection of analysis software, Mechanical Engineering, 9 (3), 42 43, March, (1987).