Integration of Daylighting and Building Lighting

Abstract

Lighting in commercial buildings consumes 25% to 60% of the electric energy utilized. Any attempt to reduce this must necessarily include integration of the cheapest (insofar as energy is concerned), most abundant, and in many ways, most desirable form of lighting available—daylight. This is most applicable at the perimeters of buildings; yet, even the interiors of low-rise buildings can be served with daylight for the general or overall illumination, using small individually controlled high-efficiency electric lights only where and when needed. As with many such substitutions, the designer must consider the tradeoff, will more glass required to admit daylight produce greater heat loss on winter nights and undesired heat gain on summer days? Techniques such as protecting glass against heat loss with insulating shutters and designing windows to minimize summer solar gain need to be evaluated.