NFRC - National Fenestration Rating Council

http://www.nfrc.org

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

NFRC provides the standard for determining and communicating the energy performance of fenestration products (windows, doors, skylights and curtain wall systems).  NFRC also administers a certification and labeling program to assure accurate and credible energy performance ratings for fenestration products.

NFRC is required for achieving compliance with the IECC (International Energy Conservation Code) and the IRC (International Residential Code); as well as other enforced state codes (such as Title 24 in California).

Without the NFRC label, a builder cannot know if the product truly meets code requirements. If a builder is trying to achieve "green building" levels; the only credible way to determine fenestration performance is through NFRC.