Energy Performance Terms for Your Home Windows

Posted: Aug 27, 2012
Author: G&S Contracting, Inc.

Choosing new home windows can be a lot of fun; the windows on your house are one of the most expressive features, and there are so many decorative options.

But there are also a lot of technical terms and measurements with which one should be familiar if wanting to choose the most energy efficient and durable home windows.

The National Fenestration Rating Council (NFRC). The NFRC is a non-profit organization that monitors the energy-efficiency ratings of windows, skylights, etc. They provide standardized ratings, so that the consumer and other interested parties may accurately compare one window to another, especially in terms of energy efficiency.

 U-factor/U-value. The U-factor or U-value is a term used to express the amount of heat energy a window will let through itself and into or out of the room. A lower U-factor means better insulation. Look for the NFRC logo to make sure the U-factor of the window is in accordance to industry standards.

R-value. The R-value is the measurement of how well an indoor space resists heat transfer. It is inversely related to the U-factor, meaning a higher R-value means better insulation.

Solar Heat Gain Coefficient (SHGC). The solar heat gain coefficient is a number between 0 and 1 referencing the amount of heat from the sun that a window will transfer through itself to the other side (1 is the most heat, 0 is the least). In the winter, a higher SHGC may be desirable, as warmth from the sun can help to heat your home. But in the summer, a lower SHGC will keep the warmth out of your house. When choosing home windows and SHGC's, keep in mind factors such as orientation to the sun, shade, climate, and location of the window.