Most Americans are probably aware that they can save energy and
create a more comfortable indoor living environment by
installing double pane windows, but by using spectrally
selective coated glass, a double-paned window can save even more
energy.
Spectrally selective glass, also called Low-E (lower emittance)
glass, has a microscopic coating applied to the glazing that
allows selected portions of the solar spectrum to pass through
it, while restricting others. The lower emittance of solar heat
in and outside the home will keep certain homes warmer in the
winter, and others cooler in the summer depending on the
climate, and will continually save money year after year over
traditional glass. This is not the dark shaded glass of the
past, in fact, today's Spectrally Selective glass appears
virtually clear, allowing the daylight to brightly illuminate
the home, making the most use of the sun's light to reduce
indoor lighting cost.
There are varying types of Spectrally Selective Low-E coatings,
with each variant more suitable for a particular climate zone.
Windows that are energy efficient in Arizona, will not be
appropriate for use in Maine. The Federal government's Energy
StarŪ program lists four climate zones in the United States and
a recommended glass type for each. In order to gain the coveted
Energy Star qualified rating, new home builders must install the
Low-E glass determined for their particular climate zone.
For example, in the North/Central region of the country, Energy
Star recommends, "Moderate Solar Gain Low-E Windows" which
screen out a selected portion of the sun's heat in the summer,
but allow a good amount of solar heat in winter. The inside
window glass stays warmer, so you're not constantly feeling that
drafty pull of chilly air assaulting your body, even though your
thermostat is at 70 degrees.
In the Southwest portion of the country, energy efficient
builders such as Pardee Homes (http://www.pardeehomes.com) use
"Low Solar Gain Low-E Windows" which will screen the most heat
from the sun and offer the greatest energy savings by keeping
the home cooler during hot summers. These coatings also block
ultra-violet rays, which greatly reduce the fading of fabrics,
floor coverings, artwork, and window treatments.
For more information on Spectrally Selective Low-E glass, and
other ways to save money by saving energy visit EnergyStar.gov.
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