ENERGY STAR ® Efficient Windows Performance Guidelines
ENERGY STAR ® is the symbol used for the government backed guidelines in energy efficiency. The guidelines are there to help protect the environment and save consumers money through energy-efficient products. Energy efficient replacement windows meet these guidelines by being manufactured by energy star partners and individually tested and certified by the NFRC (National Fenestration Rating Council).
2 Elements are needed to qualify a window for the ENERGY STAR ® rating
U-Value (insulating value) – The rate of heat loss is indicated in terms of the U-factor (U-value). The lower the U-factor, the greater a window’s resistance to heat flow and the better its insulating properties.
SHGC (solar heat gain coefficient) – The amount of solar radiation transmitted through the window and released inwards. The lower the SHGC number indicates less summer heat entering the home.