Quality lighting starts with well designed daylighting. Daylighting goals can be accomplished using a variety of apertures including windows, light shelves, advanced skylight systems, light pipes, atria, courtyards, and transom glass atop partitions.
Windows
Windows are most effective when they introduce daylight very high into a space. Variations on windows include clerestory and roof-monitors, which are vertical windows installed in articulations in the roofline.
The effectiveness of windows as daylighting apertures depends on their orientation.
North-facing windows are good sources of daylight. The sun hits north windows only in the early morning or late evening, and then only at a very oblique angle. The diffuse, indirect sunlight coming from the north prevents the glare and heat gain of other orientations, and no overhangs, shades, or special glazing treatments are required.
South-facing windows require shades to control direct solar gain in the winter, when the sun is low in the sky. South-facing windows receive maximum sun at midday in winter, and are essential components of a passive solar heating strategy. In summer, overhangs over south-facing windows are effective at blocking direct solar gain. Specific overhang geometry is calculated using the sun angle equations.
East-facing windows receive maximum sun and very low sun angles on summer mornings. West-facing windows receive maximum sun on summer afternoons. In general, low sun angles are a source of glare and unwanted heat gain, and east- and westfacing windows would be minimized depending on the views and other program requirements. However, in some climates, such as the high desert, some heat gain in the morning mitigates the night chill, and may be acceptable. Views can often be framed in small windows to avoid the problems that large windows or floor-to-ceiling glass would create on east or west faces. Where east or west windows are required, the most elegant way to reject the solar heat is with a highly reflective glass. Occupants would also use internal shades and drapes to achieve comfort.
Light Shelves
Light shelves are used to bounce light off the ceiling, project light deeper into the space, distribute it from above, and diffuse it to produce a uniform light level below. The upper surface of the light shelf would have a high reflectivity, and may be specular (like a mirror). The ceiling in the space would also have a high reflectivity, but would be diffuse (like flat, white paint).
Skylights
The sun is at its maximum on a roof during midday in summer. As a result, skylights were previously discouraged as sources of unwanted heat gain. However, new developments in glazing and shading designs have made it possible to use skylights to provide daylight above core zones in single-story buildings, or on the top floor of multi-story buildings.
Light Pipes
Getting daylight into the core of large buildings has proved challenging. Light pipes are lined with highly reflective film to reflect light down the length of the pipe from a roof aperture to a room fixture.
Light pipes are becoming popular in residential construction, and have found application in industrial facilities as well. Due to the relatively small size of each pipe, they seem to be best suited for small spaces like bathrooms or hallways.
The cost of light pipes, also called solar tube skylights, is about $450 for the plastic top dome, flashing kit, and bottom diffuser plus about $20 per foot of light pipe length for a 10" diameter pipe.
Fiber Optics
Fiber optics have also been demonstrated as a means to introduce light deep into the core of buildings, and may become feasible as glass fiber used for telecommunications becomes more affordable.
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