Which Window Ratings are Most Essential When Choosing Windows

Windows are graded in different categories used to distinguish their energy efficiency. If you are shopping for windows, greater attention ought to be placed on various rankings based on the climate the home is located in. For instance, if a person is looking for replacement windows in Phoenix, Arizona, a sunny and warm climate, the Solar Heat Gain Coefficient is perhaps the most essential category to think about. Other criteria, including the position of a window to the sun and any shade that may be present should be considered as well.

The United States Government's Energy Star program is designed to make it straight forward for persons to distinguish energy efficient goods and practices that could save them money and protect the environment. The Energy Star program rates over 60 products, inclusive of windows. Energy Star certification makes it simple for people to make certain they are buying energy efficient goods.

All Energy Star replacement windows are rated in five categories but Energy Star qualification is based exclusively on the U-Factor and Solar Heat Gain Coefficient. The U-Factor and Solar Heat Gain Coefficient are also the ratings utilized to determine if a window qualifies for the IRS Energy Tax Credit.

Indicates the rate of heat transfer and implies how efficiently the window insulates. The lower the U-Factor, the more efficiently the window insulates. The window U-Factor includes
the thermal properties of the frame along with the glazing.

Solar Heat Gain Coefficient (SHGC)
Indicates the solar energy transmitted by a window and shows how efficiently a window blocks heat caused by sunlight.

Visible Transmittance (VT)
Indicates how much light a window permits through. The higher the Visible Transmittance, the more light that is allowed through.

Air Leakage (AL)
Measures the rate at which air passes through joints in the window. AL is measured in cubic feet of air passing through one square foot of window area per minute. The smaller the Air Leakage rate, the less air leakage.

Condensation Resistance (CR)
Shows how effectively a window resists water build-up. The larger the CR factor, the less condensation build-up a window allows.

Other Window Ratings
There are other categories that are not included on the NFRC Energy Star label although they are useful and appear on some windows.

Light to Solar Gain
The ratio of Visible Transmittance to Solar Heat Gain Coefficient measures the amount of light hat is transmitted without adding heat. A larger number implies that more light is transmitted without without the addition of heat.

R-Value
R-Value was designed as a way to score insulation. It calculates conductivity and calculates the resistance to heat flow. A larger R-Value signifies better insulating properties. The majority of windows today are evaluated using U-Factor instead of R-Factor.