28. Cooling by Effective Shading

Direct sun can generate the same heat as a single bar radiator over each square meter of a surface. Shading can cool up to 90% of this heat. The big problem is that sunlight is a direct source of heat and the radiant heat from the sun passes through glass and is absorbed by building elements and furnishings, which then re-radiate it. Shading is the first step toward natural cooling in building systems. The starting point of cooling building systems is preventing sunlight from entering the building in warm periods. A shade is like putting a hat on a building. Shading must be the first line of defense against excessive heat gain. Shading in hot climate is vital. While there is no dispute about the general benefit of shading, nailing down the actual savings can be difficult. The highest priority must be placed on the surfaces that receive the most summer heat; that is, usually the east and west. The best shading occurs before the sun’s heat reaches the building. Shading is a very important method of stopping heat gain and unwanted direct sunlight by diverting the sun’s rays before entering the building. This can be accomplished with fixed and adjustable shading. Shading of the building and outer spaces can: (1) Reduce summer temperatures; (2) improve thermal comfort; (3) save building energy.