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Much of the interest in solar applications in buildings has focused on providing thermal energy to offset heating loads and, in a limited number of cases, to provide energy for cooling. But, if we look at energy use in commercial buildings, we find that lighting is a major energy consumer. As the simplest conservation measures are applied to commercial buildings, heating and cooling loads will be further reduced. Lighting will then stand out as a primary target to reduce building energy consumption.
Commercial buildings invite savings from daylighting because: they generally have long hours of daytime occupancy; the lighting power demand is relatively high on a per square foot basis; and lighting constitutes a significant fraction of the utility costs to the building owner.
Daylight and sunlight have always been desirable in homes and one need not make a case for them on the basis of daylighting savings. One note of caution in the residential sector. The notion that reducing window area will reduce energy consumption may lead us to erect houses with window areas so small that daylighting levels inside become inadequate for normal daytime use. While the use of daylight in homes is not seen as a substantial energy conservation option, to ignore or eliminate the effective use of daylight in homes would be shortsighted.