Note: State pollution emission factors are aggregated by EPA region.

at the building perimeter. Traditionally, the amount of dimming depends on the interior distance from fenestration. However, ongoing research and application of "Core Daylighting Techniques" can stretch daylight penetration distance further into a room. Core daylighting techniques include the use of light shelves, light pipes, active day-lighting systems and fiber optics. These technologies will likely become popular in the near future.

Perimeter and core daylighting technologies are technologies that are being further developed to function in the modern office environment. The modern office has many visual tasks that require special considerations to avoid excess illumination or glare. It is important to properly control daylighting in offices, so that excessive glare does not reduce employee comfort or the ability to work on VDTs. A poorly designed or poorly managed daylit space reduces occupant satisfaction and can increase energy use if occupants require additional electric light to balance excessive daylight-induced contrast.

Windows and daylighting typically cause an increased solar heat gain and additional cooling load for HVAC systems. However, development of new glazings and high performance windows has allowed designers to use daylighting without severe heat gain penalties. With dynamic controls, most daylit spaces can now have lower cooling loads than non-daylit spaces with identical fenestration. "The reduction in heat-from-lights due to daylighting can represent a 10% down-sizing in perimeter zone cooling and fans.8" However, because there are several parameters, daylighting does not always reduce cooling loads any time it displaces electric light. As window size increases, the maximum necessary daylight may be exceeded, creating additional cooling loads.

Whether interior daylighting techniques can be economically utilized depends on several factors. However the ability to significantly reduce electric lighting loads during utility "peak periods" is extremely attractive.

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