U-factor measures how well a product prevents heat from escaping a home or building. U-factor ratings generally fall between 0.2 and 1.20. The lower the U-factor the better a product is at keeping heat in. U-factor is particular important during the winter heating season.
Solar Heat Gain Coefficient (SHGC) measures how well a product blocks heat from the sun. SHGC is expressed as a number 0 and . The lower the SHGC, the better a product is at blocking unwanted heat gain. Blocking solar hear gain is particularly important during the summer cooling season.
Visible Transmittance (VT) measures how much light comes through a product. VT is expressed as a number between 0 and 1. The higher the VT , the higher the potential for daylighting.
Credits to NFRC
