National Fenestration Ratings Council
|An independent body which tests the energy performance of replacement windows and whose ratings are used for the Energy Star Program.|
The National Fenestration Ratings Council (NFRC) ratings based on it's testing and certification determine whether or not a window will be assessed as an Energy Star window. The Energy Star program provides information to consumers that allow them to purchase quality energy efficient window products. In addition to the knowledge that Energy Star windows deliver top energy performance, homeowners who purchase Energy Star replacement windows are frequently eligible to claim part of the purchase price of the window as a tax credit on their federal income tax forms.
 National Fenestration Rating Council
The National Fenestration Rating Council (NFRC) is a non-profit, third-party organization which rates and labels windows. Its assessment looks at the window product's ability to provide protection from weather elements as well as to prevent heat transfer. The NFRC provides these ratings in order to help consumers compare the performance of replacement windows and identify NFRC-certified windows which may make them eligible for tax credits and other rebates.
Fenestration refers to applications that fill openings in a building such as doors, windows and skylights. These openings permit the passage of air and light as well as people or other objects.
The United States Department of Energy estimates that homeowners can recoup the cost of an enhanced energy efficient window product within four to seven years through reduced energy bills.
 Rating Elements
The NFRC rates a window's U-Factor, it's solar heat gain coefficient, its visible transmittance, the window's air leakage and its condensation resistance.
The U-Factor is a standard industry measurement that rates how well a window product prevents heat from escaping. The rate of heat loss is expressed in terms of the U-factor (U-value) of the window's assembly. These ratings generally fall between 0.20 and 1.20, with a lower U-value offering greater resistance to heat flow and better insulating value.
 Solar Heat Gain Coefficient
The solar heat gain coefficient (SHGC) measures a product's ability to block heat caused by sunlight. The SHGC is the fraction of solar radiation which is both directly transmitted and absorbed through a window and which is subsequently released inward. SHGC is indicated as a number between 0 and 1. Lower SHGC ratings transmit less solar heat into the house. Homeowners in different climates will look for differing SHGCs, based on the needs of their particular climate.
 Visible Transmittance
Visible Transmittance (VT) assesses the amount of visible light that is transmitted through a window. VT is expressed as a number between 0 and 1 with high numbers indicated a higher light transmission.
 Air Leakage
Air Leakage (AL) is expressed by indicating the amount of air which passes through the window opening. Heat gain and loss occur when air infiltrates through cracks in the window assembly. Lower AL ratings alert buyers that there is less air passing through cracks in the window assembly.
 Condensation Resistance
Condensation Resistance (CR) measures the capacity of a window's frame, weatherstripping, spacer and glazing to resist the formation of condensation on the interior surface of the window. Higher CR ratings indicate that a window is more successful in resisting condensation formation. The rating is not meant to predict condensation, but rather to compare the various window products to assess their potential for condensation formation. CR is indicated as a number between 1 and 100.
The National Fenestration Rating Council does not provide recommendations about replacement windows, nor does it set performance standards. The responsibility of the NFRC is limited to testing and rating replacement windows and assigning them a rating based on that testing.