Windows: a major component of your home's energy efficiency

December 22, 9:49 PMHousing ExaminerDena Kouremetis

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Window shopping – one of your favorite pastimes during the holiday season? How about shopping for real windows?

At the risk of sounding like Tom Hanks’ character in Forrest Gump, describing every imaginable shrimp dish on earth, there are a huge variety of window types out there; windows with metal, wood, vinyl, fiberglass, and composite frames; windows with single-pane, double-pane, or triple pane glass, and feature gas fills, tints, and special coatings.

Now for a bit of window-ology. Each type of window allows heat, light, and air to pass through in varying amounts, which affects how comfortable your house is in both winter and summer. This, of course, can affect your utility costs as well. To make sure you are buying a home with the appropriate type of windows, you have to match your needs with the different features available. This can include the ability to keep heat in the winter, block out the sun's heat in the summer, prevent fading of fabrics, furniture and cabinets, or provide an ample amount of natural light without glare.

First, check out the direction towards which your windows will face; in other words, let the sun be your guide. South-facing windows get the most direct sunlight overall, but this "solar gain" differs in summer and winter. The dramatic differences in exposure and heat gain can mean that the right window on one side of your house may not be appropriate for the other. Compensating factors for this may be the size of the windows, trees, shading devices, overhangs and other buildings blocking sunlight.

The many new window technologies on the market are important scientific advancements, but the terminology and ratings can be confusing to understand. The National Fenestration Rating Council (NFRC) has developed a rating system and energy information labels to help consumers better analyze their choices. These NFRC ratings are always available for the whole window, including the frame.

"Low -e" (low emittance) coatings are an incredible phenomenon in window technology and energy efficiency, making their debut within the last decade in the homebuilding industry. Windows with these applications are like outfitting your new home with a pair of sunglasses year round. The coating is a clear, microscopic layer of metal oxide installed on one of the glass surfaces of a window to reflect radiant heat.

Window frames are a close second in importance to the window itself, as they can account for about 15% of the energy loss through a window.  The new gold standard is rapidly being won by windows that feature wood on the inside and specially treated aluminum materials on the outside, since the primary objection consumers have about wood windows is paint maintenance.  

Tom Nelson, regional rep for northern California's Hull’s Norcal Window and Door, explains, “These frames offer the thermal benefits, warmth and beauty of real wood on the inside.”  Manufactured by companies such as Loewen and Jeld-Wen, these never-paint windows are available in up to 20 wood-imitation exteriors colors such as Douglas fir, alder and pine, with matching authentic wood on the flip side for interiors.