The ENERGY STAR® Most Efficient 2015 designation recognizes the most efficient products among those that qualify for the ENERGY STAR program.
ENERGY STAR® is a joint program of the U.S. Environmental Protection Agency and the U.S. Department of Energy, helping consumers save money and protect the environment through energy-efficient products and practices.
Window configurations (frame, sash and glazing assembly) must meet a specific government U-Factor determined by regional climate conditions. Much like the more familiar R-Factor for walls, roofs and insulation, a U-Factor is used to express the insulation value of a window, however, conversely to R-Factors, the lower the U-Factor, the better the insulation value. Be sure to check the ENERGY STAR® requirements in your specific climate area.