What are the Different Energy Efficient Ratings for Windows

Energy RatingsBeing energy efficient with your house not only helps you stay comfortable inside your home, but also saves money and energy. It’s win-win situation no matter which way you look at it. This article is a guide to the different energy efficiency ratings for various windows, what they mean, and other resources about energy efficiency windows.

First things first-not everyone lives in the same place. Use EnergyStar’s geographic guide here to confirm which zone you live in. There are four zones to the United States, Northern (almost everything above the Rust & Sun belts), North-Central (California, the Rust Belt), South-Central (Texas, Southern California, and the South-East) and finally South (anywhere touching the Gulf, Hawaii, and some of the southwest). This is important, because each zone has different needs. For example, people in hot desert climates like the South or South-Central regions would prefer UV protection over something like condensation protection as someone in the North would.

The National Fenestration Rating Council (NFRC) is a non-profit that independently rates, tests, and provides literature about the energy efficiency of windows, doors, and skylights. The NFRC’s mission is to provide consumers with the most up to date, accurate, and honest information about the energy efficiency of the windows and other products they are buying. The NFRC regulates and monitors who and what receives an EnergyStar sticker and certification. Windows evaluated by the NFRC typically have lower numbers on the various scores meaning that they require you to use less energy.


U-Factor: U-Factor values range from scores of .25-1.25 and measures the rate of heat transfer, telling you how well the window insulates. The lower the score, the better the window insulates.

Visible Transmittance:

VT is a measurement of the amount of sunlight the window lets through and are measured on a scale of 0-1 (and average between .20-.80). The higher the VT score means you see more light.

Solar Heat Gain Coefficient:

SHGC is a measurement of how well your window blocks heat caused by sunlight. SHGC is measured between .25-.80. A lower SHGC number means the window transmits less solar heat.

Air Leakage:

An obvious, yet important factor when buying windows. Air leakage measures the rate air passes through the joints in a window.

Benefits of Energy Efficient Windows:

Upgrading to more energy efficient windows has a variety of benefits, first saving on heat / AC, which the US Government estimates 45% of a households electricity costs come from, according to the National Fenestration Rating Council. Some windows can block up to 99% of UV rays, which would save all your pictures, posters, and furniture from getting faded by the sun.

With climate change and unstable economies knocking on our door daily, there should be zero question about whether you should upgrade to more energy efficient windows. The numbers may not look like much at first, but after five, ten, or fifteen years those costs add up to a significant sum. Households with energy efficient appliances and features not only add value to your home, but also save you on your electric bill.

Related Resource: Roller Door