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New Windows that Qualify for ENERGY STAR®

To help consumers in your local area understand energy efficient windows, doors and skylights, the Department of Energy (DOE) and the Environmental Protection Agency (EPA) have developed an ENERGY STAR designation for such products. The energy performance of windows varies by climate, and change accordingly in different U.S. climate zones. Check for products that qualify in your local climate zone by reading the ENERGY STAR label to see your area is highlighted on the climate zone map.

U-Factor

The U-Factor is the rate of heat loss. The lower the value means better efficiency and the better insulating value.

Solar Heat Gain Coefficient (SHGC)
The SHGC is the fraction of incident solar radiation passed through a window. It includes both directly transmitted and absorbed along with subsequently released inward. SHGC is a number between 0 and 1. The lower a window's solar heat gain coefficient, the less solar heat it transmits.

Visible Transmittance (VT)

The visible transmittance (VT) is an optical property that indicates the amount of visible light transmitted. It includes the whole window, including the frame, which blocks all light. While VT theoretically varies between 0 and 1, most values among double -pane windows are between 0.30 and 0.70. The higher the value, the more light is transmitted.

Air Leakage (AL)

Air Leakage (AL) is through the cracks in the window?s complete assembly. Heat loss and gain occur by infiltration through these cracks. It is indicated by AL expressed as the equivalent cubic feet of air passing through a square foot of window area. The lower the AL, the less air will pass through cracks in the window assembly.