Traditional buildings made good use of renewable energy in the form of day lighting, because there was no electric lighting. If you wanted good lighting you had to incorporate high windows and skylights in your home.
Typical outside brightness is 10 to 50 times as bright as a comfortable interior brightness. This is why day lighting of interiors can be so effective.
A modern wrinkle on day lighting is the use of electric lighting controls in conjunction with day lighting. When day lighting is strong, the controls dim or turn off the electric lights to maintain a pre-determined interior lighting level. This control technique is termed “daylight harvesting.”
High windows are an excellent way to gather daylight. This feature is especially prominent in factory buildings built in the good old days before electric lighting.
High windows often have a view of the bright sky and can gather lots of light.. Since they light from above and do not glare directly into your eyes, they are effective for general background lighting in a home.
A high window also has a potential advantage in high-low window ventilation. The most efficient way to cool a house is to exhaust hot air at a high location while letting cool air in from a lower location.
A solar tube is a clever skylight with a diameter ranging from 8 to 24 inches. It consists of three components: a roof-mounted sunlight gathering dome, a high reflective tube (usually 6 to 12 feet long) to channel the sunlight, and an interior diffuser.
The ability of the reflective tube to channel light around a bend provides flexibility in positioning the interior diffuser. The diffuser does not have to be right below the skylight, and construction obstacles in the attic can be avoided.
The interior white plastic diffuser has the appearance of an ordinary light. Sometimes the diffuser includes an auxiliary electric light for night-time use. A tubular skylight may provide the lighting power of 1 to 10 conventional 100-watt light bulbs.
The limited outside exposure of the solar tube makes it energy efficient. Heat gain and heat loss are limited. This is a big advantage over larger ordinary skylights.
A skylight is basically a window set into a roof.
Skylights are an excellent way to brighten a room. Compared to electric lighting, they can bring in huge amounts of light. For example a small sunlit 2.5 by 4 foot skylight can illuminate the home with the light equivalent of 60 ordinary 100-watt light bulbs. Even on a dark cloudy day a skylight could gather the light equivalent of 6 light bulbs.
A skylight’s excellent light gathering ability can be a detriment on hot sunny days when overheating can occur. This problem can be mitigated by installation of a good quality skylight. A double-glazed window with low e-coating can minimize summer heat gain while still letting in lots of light; a sunshade is another cooling option. A skylight with good insulating qualities can also minimize winter heat losses.
Skylights are vulnerable to air infiltration and water leakage. This is why it is very important to purchase a very high quality skylight and specify a very careful professional installation.
For all the above reasons, it is important not to oversize skylights. High windows are a preferred alternative for most room lighting needs.
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