THE
ENERGY
FACTOR
By now, almost anyone who’s
researched home-related prod-
ucts is familiar with ENERGY
STAR ratings. For the past 27
years, ENERGY STAR has been
evaluating everything from
appliances to structural compo-
nents using a rating system
that informs buyers about the
energy benefi ts of these items.
When window shopping,
there are a three key indicators
you should know in addition to
the rating ENERGY STAR gives
a specifi c product to help you
make a fully informed decision:
R-Value. Most commonly
associated with insulation
products, windows, too, have
R-values that measure the re-
sistance to heat transmission.
A high R-value means that less
heat fl ows through the glass.
U-Factor. Also known as
thermal transmission, U-factors
measure how well a window
prevents heat from escaping.
Unlike R-value, the lower the
U-factor, the better.
SHGC. This abbreviation
stands for Solar Heat Gain
Coeffi cient and measures the
fraction of the solar radiation
admitted through a window. A
lower SHGC number signifi es
better blocking power. This is
especially important in a room
that boasts walls of glass, like
a great room. If you want to
hold the heat in during the
winter, opt for a higher rating,
while those wanting to lessen
their cooling needs in summer
should choose a lower rating.