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Tropical Design Module 4: Passive CoolingPassive Cooling

A cooling system using a buildings design and construction to maintain a

comfortable temperature within the building.

Passive design is essentially low-energy design achieved by the buildingsparticular morphological organization rather than electro-mechanical means.

Passive Cooling Techniques

1. BUILDING CONFIGURATION, SITE LAYOUT and SITE PLANNINGExample : A building can be protected from direct sunlight by placing it ona location within the site that utilizes existing features such as trees, terrain etc.

2. BUILDING ORIENTATIONExample : In tropical countries such as the Philippines, it is besttoplace service areas in the west and east facing sides of the building becausethese sides are exposed to direct sunlight.

3. FACADE DESIGNUse of Double-layered faadeUse Low-emissivity glass (Low-E glass)Use of Insulation

4. CROSS VENTILATIONThe circulation of fresh air through open windows, doors or other openings onopposite sides of a room

STACK EFFECT / CHIMNEY EFFECTThe tendency of air or gas in a shaft or other vertical space to rise when heated,creating a draft that draws in cooler air or gas from below

5. SUNSHADING DEVICESVERTICAL TYPESVertical Sun Shades are generally used on the East-Facing and West- Facing Sides

of a buildingEGGCRATE TYPESCombination of Horizontal and Vertical Shades

WIND ANALYSISWind direction: Desirable and undesirable winds in each of the climatic zonesdepend largely on local conditions. Any breeze in the lower latitude (tropical and

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arid climates) is beneficial for most of the year.Cross ventilation: Cross ventilation is far more important in the tropics than intemperate zones. The theoretical strategy for blocking or inducing wind flow intoa building is based on local prevailing wind conditions. Generally, for the tropicalzones as much ventilation as possible is desired.

Influences on Built Form1. Zoning for transitional spaces -the traditional spaces used for lobbies, stairs,utility spaces, circulation, balconies and any other areas where movement takeplace. These areas do not require total climatic control and natural ventilation issufficient. For the tropical and arid zones, the transitional spaces are located onthe north and south sides of the building where the sun's penetration is not asgreat. An atrium can also be used a transitional space.

2. Use of atriumIn the tropical zone the atrium should be located so as to provide ventilationwithin the built form. In the arid zone the atrium should be located at the centreof the building for cooling and shading purposes.

Influences on Built Form1. Form: Optimum building form for each climatic zone. Research has shown thatthe preferred length of the sides of the building, where the sides are of length x:y,are: tropical zone - 1:3

Analysis of these ratios shows that an elongated form to minimize east and westexposure is needed at the lower latitudes.

2. Orientation: Orientation as well as directional emphasis changes with latitude inresponse to solar angle. Building's main orientation for tropical countries wouldhave a directional emphasis on an axis 5deg north of east

3. Vertical cores and structure The arrangement of primary mass can be used as afactor in climatic design as its position can help to shade or retain heat within thebuilding form. For the tropical zone, the cores are located on the east and westsides of the building form, so as to help shade the building from the low angles ofthe sun during the major part of the day.