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Features to look for in
energy efficient replacement windows
 Some
of the features to look for in energy-saving replacement windows
The technology of windows has improved greatly in recent years. As a
result, we have reaped the benefits of lower energy bills.
Listed below are some important energy features that have occurred for
replacement windows:
Multiple layers of glazing:
Manufacturers in the 1980s improved energy performance of windows by
adding additional layers of glazing. Some of window used only glass as
an insulation. Others used a thin film of plastic. Double-glazing works
twice as well as single glazing and adding a third or fourth layer of
glazing we see even more improvement.
Thickness of air space:
Double-glazed windows have air space between the two panes this air
space provides the insulation. However, if the space is increased over
1, you do not increase you energy efficiency. Manufacturers in the 1970s
increased the thickness from ¼" to ½" of the air space in double-glazed
windows or more. If the air space is too wide, however, condensation,
the process a gas or vapor turns into liquid, forms between the layers
of glass.
Low-conductivity gas fill:
To reduce heat even more, the air sealed between the insulated glass
windows was replaced with low conductive and dense gas, such as argon (Ar),
carbon dioxide (CO2), sulfur hexafluoride (SF6), krypton (Kr), and
argon-krypton mixtures. The major manufacturers offer argon gas-fill as
an option.
Tinted glass coatings:
To reduce heat gain, tinted films were applied to windows in commercial
and some residential buildings. Not only did the film reduce heat, it
also restricted visibility. Over time, some films bubbled and peeled
from the glass. Today, improved lighter tinting lessens solar heat gain
without limiting visibility and does not bubble and peel away from the
window.
Low-e Coatings:
In the 1980s low-emissivity (Low-E) coatings technology was developed. A
thin, coatings of silver or tin oxide is placed on the window. This thin
transparent coating does not restrict visibility or light from passing
through the window. Low-e coating reduce heat lose through the windows
by reflecting the solar heat back into the room.
An assortment of low-e windows exists for various climates and different
functions in any specific place. Northern climates require low-e windows
that have high solar gain coefficients. What does that mean? Solar gain
coefficient is the rate of heat loss in BTU (British Thermal Unit) per
hour through a square foot of surface when the difference between indoor
and outdoor air temperatures is one degree oF. Southern climates where
cooling is important require low-e windows with low heat gain
coefficients.
Because not all sides of your home face the same direction, it is
desirable to choose windows with different low-e glazings for your home.
Builders and Contractors canget a better price for a batch of windows
that are the same type, because of this; it may be complicated to find a
contractor or builder who is willing to customizing your window
installation. From an energy perspective, it would be best that you
consider this option. Example: The southern exposure of your home should
have low-e glass with a high solar heat gain coefficient installed. The
side of your home with a northern exposure should have the lowest
U-value windows installed, the east, and west windows can be of the same
U-vale as your northern windows.
Most window companies that manufacture low-e products for both the
northern and southern climates. Some manufacturers offer one form of
low-e glazing. This is their standard window. If you want or need a
different low-e glazing, you will be charged extra, providing that they
offer this option. Therefore, before you make a chose a particular
company, shop around. The Internet is a wonderful place to do this.
Here, you can research different window manufactures, compare their
products and make an educated decision. On most manufactures websites,
they also offer a list of qualified/ certified installers and suppliers.
When you do purchase
multiple windows with different glazings, make a chart or list of which
windows go where.
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