Natural Cooling of Malaysian Urban Homes by Free Wind

By Dr. Abdul Malik Abdul Rahman
November 1999

The Author is the Deputy Director of the Center for Education, Training and Research in Renewable Energy and Energy Efficiency (CETREE), as well as Practicing Architect and Lecturer at the School of Housing, Building & Planning of Universiti Sains Malaysia (USM) in Penang. His special interests is in indoor thermal comfort for Malaysian homes without the use of mechanical aids. Identifying which mode is most effective in a climate where fifty percent of the wind condition is calm. → See also:

There are different types of Tropical climates varying from the hot dry to the hot humid. It is the hot humid which has posed difficulties in achieving a thermally comfortable environment indoors. Many ways were resorted to and the easiest ways were to consume electricity to operate fans and air-conditioning. These add to running costs. This paper suggests a possible and promising way to cool interiors by natural means and at this stage it is still being experimented.


Cooling Malaysian urban homes by natural means has always been a great challenge to many architects and mechanical engineers. Ceiling and/or portable fans and air conditions are some of the ways to displace hot internal air with fresh external air thereby cooling off the internal building fabric and also acting as a catalyst in evaporating moisture from the human skin. Both ways entail running costs. Between the two, the fans have always been cheaper than any other means. It is highly unlikely that we can be thermally comfortable indoors without the mechanical aids.

The tropical climate is not only hot throughout the year with little temperature difference, but also very high in humidity (>80%). The average maximum temperatures occurs for about six to seven hours during daytime correspondingly with low relative humidity (approximately +/-60%). Cooling is needed during daytime to counter the radiant heat from the searing heat of the sun. Conversely, the average maximum relative humidity occurs during the midnight hours. Cooling is needed during these hours to counter the high relative humidity in the air which is not conducive for comfortable sleep.

Current Conditions

Most homes in Malaysia are constructed with construction materials which absorbs heat readily from the sun during the daytime. At night time, the air outside cooled rapidly, but the building fabric behaves differently where heat is released from the building mass to the surrounding air indoor and outdoor. This thermal behaviour is typical of houses predominantly built of highly densed materials such as clay and cement bricks, concrete and also lightweight concrete aggregate. Figure 1 shows the thermal performance of the different types of domestic dwelling viz., the traditional Malay attap roof house, the traditional Malay zinc roof house, the low-cost cluster house, the low-cost walk-up flats and the low-cost terrace. The attap and zinc showed extremes of temperature both daytime and night time with temperatures soaring up to above 33oC internally during daytime and below 26oC internally during night time. This extremes was due to the nature of the construction materials which are of thin veneer type of timber planks for walls and attap and zinc for roofs. So the absorption and the release of heat was rapid to equal to outside temperatures. Unlike the three other houses of the heavily masonry type of construction where absorption and release of heat was of a graduaal meovement. Figure 2 shows the behaviour of thermal performance of those houses under investigation on the hourly basis. The night time behaviour of the modern houses have failed in releasing heat rapidly from the building fabric thereby causing discomfort having higher internal temperatures than the external condition.

Figure 1: CET mean daily maximum & minimum for the five houses based on the data from the monitoring experiment¹
Figure 1

Figure 2: Period average inside to outside temperature differences for the measured cases²
Figure 2

Possible Solutions

Apart from tapping the energy from the sun to produce electricity via solar cell panels which at the moment only the wealthy can afford, there are other passive and cheaper means of reducing the heat load of the building interiors. One of them is the use of the turbine ventilator (Figure 3) which is gaining popularity. It uses the principle of the stack effect from inside the building and together with the aid of light wind speed from outside to siphon out hot air. One thing it does not do is to generate ample air movement for evaporative cooling.

Figure 3: A typical turbine ventilator
Figure 3

Another possible alternative is to use the uninterrupted wind speed high up in the altitude. It is an acceptable fact that wind speed increases the higher the altitude because of the absence of land mass and built-up areas nearer the ground (Figure 4). The Idea is to use the principle of the wind vane (externally located) by rotating the fan (internally located) simultaneously as the wind vane rotates. This idea is presently being researched into for further development to make it more efficient. Depending on the location in Malaysia wind is relatively calm for almost 30% to 50% of the year. Calm condition is considered to be less than 0.3m/s by definition. And when there is wind, its speed varies and can come from different directions, all within a day (Table A & B). In theory the principle works, as shown in Figure 5. There are variables that needed to be specified before it could reach marketability.

Figure 4: Altitude and wind speed³
Figure 4

Table A: Wind speed in strategic locations in Malaysia4
Location Period Wind Speed
<0.3m/s in %
Mersing 1968 - 1987 2.4
Kota Kinabalu 1968 - 1987 11.0
Tanah Rata 1984 - 1988 12.5
Ipoh 1968 - 1988 13.7
Kluang 1974 - 1987 14.5
Kuala Trengganu 1986 - 1988 15.0
Sandakan 1968 - 1987 15.0
Penang 1968 - 1988 18.9
Kuantan 1968 - 1987 21.6
Malacca 1968 - 1987 21.8
Alor Star 1968 - 1988 22.8
Miri 1968 - 1987 24.8
Butterworth 1985 - 1988 26.3
Kota Bharu 1968 - 1987 28.5
Bintulu 1968 - 1987 30.9
Kuala Kerai 1985 - 1988 32.4
Sitiawan 1968 - 1987 35.0
Kuching 1968 - 1987 35.1
Petaling Jaya 1974 - 1988 38.0
Johor Baru 1975 - 1988 39.7
Muadzam Shah 1984 - 1987 43.0
Batu Embun 1983 - 1987 46.5
Kuala Lumpur 1968 - 1988 46.7
Temerloh 1979 - 1987 50.4
Table B: Variable wind directions in major Malaysian cities5
Month A.Star K.Lumpur K.Bharu Mersing B.Lepas
January NE/E NE E/NE N/NE Variable
February NE NE E N/NE Variable
March NE Variable E/NE N/NE NE/N
April Variable Variable E/NE W SW/W
May W Variable SW/S W/SW SW/W
June W S SW/S SW/W Variable
July W S SW/S SW/W Variable
August W S SW/S SW/W Variable
September W S SW/S SW/W SW/S
October Variable Variable SW W/SW SW/S
November NE W E/NE W Variable
December NE NE E/NE N/NE N/NE

Figure 5:
Diagrammatic theory of the free wind fan
Figure 5

Free wind fan is stationary when there is no wind outdoor but creates wind or air movement indoors in tandem with the wind vane up on the roof. This idea is useful in a row of terrace houses where the intermediate may not be able to relieve any wind or cross ventilation from the longitudinal direction, without the aid of a free wind fan. Thus with a free wind fan on the roof we can transfer the wind energy indoors to aid movement indoors... where air movement of a speed as fast as 1.5m/s is sufficient to provide thermal comfort in Malaysian indoor climate.

These variables would likely to be:

  1. At what height of the wind vane should be to capture the constant flow of wind?
  2. The weight of the whole contraption, it should be lighter and durable.
  3. Should it be employing the stack effect or generate air movement?

Consideration 1, would vary depending on the location of the proposed building. If building were to be by the coastal areas, its height need not be high for obvious reasons. For buildings in the urban context, height is critical.

Several advantages could be gained from this contraption:

  1. The speed of wind at the high altitude can be transferred to the lower altitudes to generate the same speed. This required speed is scarce at ground level.
  2. The speed can be constanr or vary but never calm. Air movement provide fresh air in an cool the interior structures thereby reducing the internal heat load.
  3. Could still generate a good amount of air movement even when windows are closed during rainy days.
  4. Reduce electricity bills.
  5. Maintenance free.


  1. Abdul Malek Abdul Rahman, "Design for Natural ventilation in Low-Cost Housing in Tropical Countries", University of Wales College of Cardiff, A PhD Thesis, 1994.
  2. Ibid.
  3. Michele G. Meloragna, "Wind in Architectural and Environmental Design", Van Norstrand Reinhold Company, 1982.
  4. A.M.A. Rahman, "Unsuitability of Low-Cost Cluster-Link House in the Hot Humid Climate of Malaysia". Journal of HBP, Housing, Building & Planning, Volume II, ISSN:0218-6536-1995.
  5. Ibid.


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