Understanding Window-Efficiency Ratings


Quality windows will ensure that your home realizes great savings over time through increased energy efficiency. But understanding the ratings and terms for good quality, energy efficient windows can be a little daunting.

The first step is to know how to compare the efficiency of windows. The National Fenestration Rating Council (NFRC) has developed a nationally recognized rating and labeling system for the energy performance of windows so that consumers can easily compare their window options. The other major label that you need to look for is the U.S. Department of Energy’s blue-and-yellow Energy Star label. This will tell you whether a product meets important standards.

Now that you know what ratings to look for, the next step is to understand what those ratings mean. There are two major traits that you need to observe:

1. U-factor: This is the Solar Heat Loss Coefficient. Ideally you want a number that is below 0.3 because it reflects the insulator quality of the window. For example, less heat will escape during the cold winter months.

2. SHGC: This is the Solar Heat Gain Coefficient. It falls between the numbers of 0 and 1; if you live in a warmer climate, then you will want a lower SHGC because this number reflects the solar radiation a window allows inside.

There are also a few other performance ratings that are worth your attention (though the two aforementioned ratings are the most important).

Air Leakage (AL): This rating will basically tell you the extent to which a window is airtight. A lower AL value indicates less air leakage.

Visible Transmittance (VT): This measurement tells you the amount of light the window lets through. A higher VT measure means the more light you see. In comparison to the past, various types of coating now allow windows to let light in without getting the room too hot.

When it comes to choosing the type of glass, it is best to have two and three panes because single pane glass is highly inefficient. Argon-filled glass windows are energy efficient because argon serves as a strong insulator.

If you doubt your ability to properly install windows, then it’s best to hire a professional; otherwise, a “do-it-yourself” installation may lead to loss of efficiency if mistakes are made.

Understanding energy efficient ratings is also important for your wallet, as there are tax credits available for eligible windows. Information on tax credits can be found here: http://www.resnet.us/library/energy-tax-credits-mortgages/

John A Silva
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John A Silva

John Silva has over 21 years experience in residential real estate. He is a San Diego native, specializing in helping sellers & buyers, with extra experience in: modifications, short sales, and negotiation.
Contact me today for real estate assistance! (619) 890-3648 | Email me
John A Silva
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  1. Pingback: Understanding Window-Efficiency Ratings « roberrodris

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