2. DAYLIGHTING AS A PASSIVE SOLAR DESIGN STRATEGY IN TROPICAL BUILDINGS: A CASE STUDY OF MALAYSIA
The second case study is located in Malaysia, in the Torrid Savanna climate; in these kinds of climates it can be useful to reduce as much as possible the internal gains, in particular the ones due to lighting appliances, so to minimize the energy needs for cooling.
The purpose of the paper \citet{surendran2002} is to describe a study on the savings achieved by using daylight in passive solar design of buildings and, in this case, the size of windows. The energy consumption for lighting in Malaysia is about 25–35% of the total energy supplied to buildings.
The building is a general office work, where light work is the main activity of the occupants. In particular, one single room occupied by two persons, measuring 3 m wide, 4 m deep and 3 m high, has been analysed. The room also contains heat generating office equipment (a photocopier, a personal computer and a laser Printer) and it has to be maintained at a constant indoor temperature of 26°C.
The interior illuminance data produced by various sizes of windows (openings of 10%, 25% and 40% window to floor ratio (WFR)) have been integrated into the cooling load calculations of simple buildings to determine how much energy can be saved. With the help of isolux contour charts, it was shown that it is possible to determine the times at which supplementary lighting is required. The number of lamps to be switched on could be ascertained from these charts and incorporated in the cooling load calculations. Examples of heat gains in the building with a glazed window opening, ranging from 10% to 100% WWR, were simulated. The additional heat gains through the opaque wall and transparent element (glazed window) were offset by the non-use or reduction in the use of electric lighting; finally, an optimum window opening has been identified. More savings could be achieved with manual controls, addition of shading devices and types of glazing to reduce solar gains but minimise optical absorptivity. It has been shown that savings of a maximum of 10% can be achieved by using daylighting strategies alone, and this savings could be even more if a combination of daylighting and shading strategies are applied in passive solar building design without compromising visual requirements.