NFRC is a non-profit organization that administers the only uniform, independent rating and labeling system for the energy performance of windows, doors, and skylights.
www.nfrc.org

Energy Star is a joint program of the U.S. Environmental Protection Agency and the U.S. Dept of Energy, helping us all save money and protect the environment through energy efficient products and practices.
www.energystar.gov

The Efficient Window Collaborative provides unbiased information on the benefits of energy efficient windows, how they work, and recommendations for their selection and use.
www.efficientwindows.org