from Dave in West Allis, WI:
#50
How much energy can I save by replacing my windows?
You could save quite a bit depending upon what type of windows you currently have.
On a very cold day, as much as 30% of your heating may be lost through your windows. Upgrading from an older single pane window to a new ENERGY STAR qualified window could save you up to $300 annually. Savings don't always occur in winter, as you might think. ENERGY STAR qualified windows keep out the heat in the summer and Low-E coatings block ultraviolet rays.
ENERGY STAR qualified windows meet criteria established by the US Environmental Protection Agency and US Department of Energy and are tailored to specific climate zones. These windows typically have two or more panes, improved framing materials and Low-E coating which keeps heat inside during the winter and outside during the summer. When shopping for windows keep in mind that not all ENERGY STAR qualified windows qualify for the federal tax credits. Windows that qualify for the tax credit must have a U-Factor (a measure of heat loss) and Solar Heat Gain Coefficient (SHGC, the measure of the sun's heat allowed into your home) of .30 or less. Be sure to read all you can before you buy because there are many factors to consider.