By REMODELING Magazine Staff. Solar Heat Gain Coefficient: Measures as a number between 0 and 1 the amount of solar heat entering through the window as well as the amount of heat absorbed and generated inward.
U-factor (or U-value): Measures heat loss. The lower the U-factor, the lower the heat loss.
Air Leakage: Measures the amount of air escaping through cracks in the window construction.
Visible Transmittance: Indicates as a number between 0 and 1 the amount of light entering through the window. The higher the number, the more light is coming through.
Photo: Courtesy NFRC