The Nation



Daylighting: An efficient energy-saving light source

Daylighting is one of the most efficient means of saving energy, as daylight can be obtained freely, unlike artificial light.

The building orientation is an important initial decision in implementing daylighting. Architects must try to position the building in a direction so as to avoid direct sunlight, especially on the building's western and southern exposures. Accordingly, heat transfer from sunlight through building envelopes can be minimised.

To design for daylighting, some basic principles stand: the maximisation of exposed surface area; the selection of building envelope to control daylight; shading the building envelope; ceiling heights; the shapes and sizes of windows; and the colour and texture of the building envelope.

For interior design, quality daylighting can promote design pragmatism, enhancing functional efficiency as well as aesthetics. For example, windows that invite daylight provide views, create atmosphere by reducing interior monotony, and promote passive energy savings through attractive use of daylight. Accordingly, the design of window openings is very important. Window heights directly affect depth of luminosity. Large windows that receive direct sunlight should be avoided. Other design considerations include the choice of glass types for windowpanes, the size of openings, and the use of shading devices, among others.

The interior designer's palette can greatly affect luminance. For instance, lighter-coloured surfaces can better reflect light than darker tones. Interior walls of translucent materials aid better daylight penetration. Shades or curtains should be used only when needed.

During the day, natural lighting might be combined with artificial lighting in areas that cannot be naturally lit. A simple energy-saving method is to design the electrical circuit in conjunction with natural illumination depth so that artificial lighting could be turned off when levels of natural illumination are sufficient. The combination of daylighting with artificial lighting can be further enhanced by the use of sensors that are strategically placed near window openings. When the luminance level dips below a certain point, the sensors automatically turn on artificial lights, thereby increasing luminance to the necessary level.

For buildings where larger floor plates preclude daylight deep in the interior or in basement floors, architects can introduce more sophisticated devices such as light shelves or light pipes. The use of solar cells to store energy to power light can also be considered.

These lighting techniques require a certain level of investment. The architect and the project owner should therefore work together for the best design solutions that are not only viable economically, but also satisfactory for energy savings.

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