Lighting from above offers the best distribution of diffuse skylight, with deeper penetration and better uniformity of daylight. Toplighting is best where light is desired but a view is not necessary. It offers better security and frees up wall space. Toplighting may eliminate the need for electric lighting on the top floors of a building during daylight hours. Unlike sidelighting, it is easy to distribute uniformly. Toplighting controls glare from low angle sunlight better than sidelighting.

Clerestories (Fig. 33-1) provide balanced daylight throughout the changing seasons better than do skylights. South, east, or west facing clerestory windows that are designed so that the light bounces against a vertical surface and is diffused on its way to the interior capture the maximum amount of sun in December and the minimum amount in June. The Johnson Controls building designed by Don Watson is an example. A light shelf (described later) and clerestories light the building during the day, and the sun striking a massive wall holds heat with only a slight difference in night temperature. Clerestories use standard weather-tight window constructions. In the northern hemisphere, south-facing clerestories provide the most heat gain in winter.

Toplighting provides more light per square foot b with less glare than sidelighting, and distributes the light more evenly. However, where the direct sun enters a skylight, it may strike surfaces and produce glare and fading. Unshaded skylights exposed to summer sun by day and cold winter sky by night lead to heat loss. High windows or toplights work best for horizontal tasks like reading at a desk, while lower sidelights (windows in walls) are best for vertical tasks like filing.


Solar Power

Solar Power

Start Saving On Your Electricity Bills Using The Power of the Sun And Other Natural Resources!

Get My Free Ebook

Post a comment