Casement Window Ratings

The NFRC

• Casement window ratings are determined by a non-profit group called the National Fenestration Ratings Council, or the NFRC. It was formed in the 1970s in response to the energy crisis and exists to help builders, contractors and homeowners make informed choices about energy-efficient windows. The NFRC also helps to establish standards for lawmakers and manufacturers.

How Ratings are Determined

• The NFRC uses product-performing tests on windows. Windows are tested for air leakage and the effects of solar heat. The NFRC has also developed a special computer program that will calculate the energy costs associated with each window, based on geographic region. Each of these factors is considered when determining a rating.

Accessing Ratings

• The NFRC has made all of its energy ratings available online. When you access their website, you can search for ratings by type of window, as well as by manufacturer. This way, you can compare the energy ratings of different brands to make an informed decision on the type of window to install.

Understanding the Ratings Guide

• Each window is rated on four different criteria: U Factor, Solar Heat Gain Coefficient, Visible Light Transference and Air Leakage. The rating for each criteria is given for both commercial and residential properties, as window sizes are typically very different for each of these building types. Each rating also includes a description of the product.