In the tropical climates, the designer should keep the solar radiation off the opaque solid elements of the building’s envelope where possible. Special care should be taken to shade the windows to reduce the incoming heat and the risk of overheating.
The design of shading devices can be quite complex. Computer programs exist to accurately shape shades for very specific purposes. However, in their absence, and with a little understanding of the mechanics of sun position and sun-path diagrams, manual methods can be used.
External shading devices are preferable and more effective than internal ones. This includes devices fixed to the outside of the window or attached to building envelope. Among the operable units are louvers made of wood or metal, exterior venetian blinds, shutters, awnings and fixed or movable overhangs.
As you should know from your own personal experience, the most important characteristic of solar position is its seasonal variation. At the height of summer in the southern-hemisphere the sun rises slightly south-east and sets slightly south-west. In winter it rises slightly north east and sets slightly north-west. It also rises much earlier and sets much later in summer than in winter. In the northern hemisphere, north and south are reversed.
The aim of good shading design is to utilise these characteristics to best advantage, usually complete exclusion in summer and maximum exposure in winter.
Rules of the thumb
Shading devices should be selected according to the orientation of the window. Whilst some orientations are easy to shade, others are much more difficult as the sun can shine almost straight in at times. The table below indicates the most appropriate type of shading device to use for each orientation in the southern hemisphere. These are guidelines and, of course, there are many variations to these basic types.
|North (equator-facing)||Fixed horizontal device|
|East or West||Vertical device/louvres (moveable)|
|South (pole-facing)||Not required|