Daylighting is an aspect of green building design that should be ubiquitous; without adequate daylighting, people will not perform well and will not be healthy. For building plans, this implies a design that is no more than 66 feet wide, front to back, or about 33 feet to a window from any workstation. This is a standard design requirement in many places in Europe, where people's health is placed before economic efficiency. Looked at another way, a building should be oriented so that the long axis is east-west; this allows for maximum daylighting, from both south- and north-facing windows.
Daylighting's benefits are immediately apparent; people see better and feel better whenever there is natural light for reading and working. Good daylighting design can employ skylights, north-facing windows on the roof, a central atrium, light shelves to bounce light into a space while shading windows from the summer sun, and other techniques. Good daylight-
ing is always indirect, without glare. Daylighting is usually combined with electric lighting, so that there is a constant lighting level, typically 30 foot-candles at the desktop, or there is task lighting provided for each workstation.
According to a report from Carnegie Mellon University analyzing daylighting research, "Eleven case studies have shown that innovative day-lighting systems can pay for themselves in less than one year due to energy and productivity benefits...the ROI [return on investment] for daylighting is over 185%."38
A California study of the impact of daylighting examined 73 stores of a chain retailer, of which 24 had daylighting. The results:
The value of the energy savings from daylighting is far overshadowed by the value of the predicted increase in sales due to day-lighting. The profit from increased sales associated with daylight is worth at least 19 times the energy savings."39
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