Energy efficient windows are a great investment and a good way to keep your home cooler when the temperature is on the rise. But we know it can be confusing to determine which type of windows are best for your needs (and your budget), so we're here to help make the process easier. The first step is learning more about ENERGY STAR rated windows, which are ranked based on a variety of technical factors we discuss in more detail below. 

The first factor is a U-factor rating.  In simple terms, this is a rating given to a window based on how much heat loss it allows, ranging from 0.2 (very little heat loss) to 1.2 (high heat loss).  The opposite of a U-Factor is an R-value, which is the window’s ability to insulate.  The higher the R-value, the better. The Solar Heat Gain Coefficient (SHGC) value indicates how much heat the window lets pass into your home from the sun. SHGC numbers range from 0 to 1; the lower the number, the less heat enters your home.

Another factor in ENERGY STAR windows is the low-emissivity (low-E) coating. Low-E coating is a thin metallic film that reflects heat back into the house in winter and blocks heat from the sun in summer. It used to be that the tinted windows best reflected the sun, but now the technology behind low-E coatings has improved such that clear glass is just as effective as darker windows. Again, think about your own climate when determining what is more important to you – more heat in the winter, or less in the summer.

Regardless of materials and ratings, your windows will be effective only if they are correctly measured and installed. You may want to consider hiring a contractor to do it for you just to make sure the added value of your windows isn’t lost by poor fit and seal.


I seek You with all my heart; do not let me stray from Your commands.  Psalm 119:10

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