Are Your Windows Energy Efficient?

When you’re choosing new or replacement windows, it’s always good to look for the Energy Star label.  But the information on each window’s NFRC label allows you to delve deeper and find the best match for your particular needs.

Hundreds of window, door and component manufacturers belong to the National Fenestration Ratings Council and submit their products to be rated for energy efficiency.  The NFRC’s distinctive label on each of its members’ windows rates several categories – different features may be more important in your particular situation, but in general all the ratings measure how well the window keeps the inside in and the outside out.

The U-Rating measures how well the window keeps heat from escaping – an especially big issue in the winter when you want to keep that expensive heat indoors.  The lower the number (on a range between 0.20 and 1.20), the less heat escapes.

The Solar Heat Gain Coefficient measures how much heat the window lets in with the light – particularly of interest in those southwest-facing windows, perhaps.  When you want to keep the A/C bills low, look for windows with a low solar heat gain coefficient.

Visible Transmittance measures (on a scale of 0-1) how much light the window allows to pass through; the higher the number, the more light is transmitted.

Air Leakage looks at one of the biggest culprits in a home’s unwanted gains and losses of heat: flow of air through less-than-perfect seals and other joints on the windows.  The lower a window’s AL number, the less air it lets through.

Consult with your local window contractors about which features are most important to your project and learn more about energy star windows.


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2 Responses to “Are Your Windows Energy Efficient?”

  1. Jerry Says:

    People who pursue ENERGY STAR ratings or “Green” products typically do so from the motivation to save energy and/or to use renewable resources – rarely is the motivation to brag about the certification itself. This is a good thing for the window tinting industry because no window tinting product is currently ENERGY STAR rated because the complicated approval process only rates the EXACT product and construction being tested and is therefore predisposed to the special interests of the window replacement industry. To get free information about window tints, visit Window tints reduce energy consumption, lower energy bills, prevent the sun from fading the interior, and maintain a comfortable, consistent and balance temperature in your home.

  2. Robert Green Says:

    Very informative article. We are constantly trying to help our client’s understand exactly these points and you have spelled them out perfectly. In the Houston and Austin areas of Texas, the Solar Heat Gain Coefficient is the number that concerns us the most (followed by air leakage possibly). We run our air conditioners constantly down here. Heating our homes is only necessary for 2 short months which makes a UF factor of around 35-40 just fine here. For the SHGC, we like numbers below 20.

    Keep up the informative postings.

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