Green Interiors

Selecting energy efficient windows
by Pamela Portwood

In the early 1980s, when my husband and I lived in Memphis in an old duplex rental without air conditioning, we survived the hot, humid summers by putting a fan in the window, hanging out in the mall and sleeping in my mother-in-law's living room. In the winter, we piled on the blankets and taped sheets of plastic over the drafty windows to keep our gas bills down and the damp cold out.

Memphis has its virtues - Beale Street and the blues, Elvis' Graceland home and the best barbeque around (according to my husband, a native Memphian), but good weather is not on the city's list of top hits.

Taping plastic over leaky windows does help in the winter, but a better way to reduce your home energy bills by up to 30 percent is to install energy efficient windows and doors. Replacing windows and doors isn't cheap and choosing the best products for your home can be confusing, but the investment can really pay off in energy savings for older homes.

To start with, windows and doors are constructed of several types of materials: fiberglass, aluminum, vinyl, solid wood and composite products that use more than one material. All of the products have their pros and cons in terms of efficiency, sustainable materials and recycling, but I can't recommend windows or doors that use vinyl. Vinyl chloride is a human carcinogen, and the process of making vinyl is water intensive and involves many toxic chemicals.

A window's glazing system (the material inside the frame, including the glass) is at the heart of its efficiency. Windows can be single paned, double paned or triple paned. The more panes there are, the more efficient the windows. The space between the multiple glass layers also can be filled with argon or krypton gas for added insulation.

Another issue is with windows is that sunshine can fade furniture, flooring and art. Low-emissivity (low-E) coatings on the window's glass can reflect heat energy to reduce fading and increase energy efficiency.

There are many statistics related to window efficiency, but two of the most important ones are a window's U-factor and its Solar Heat Gain Coefficient (SHGC). The U-factor measures the product's rate of heat loss. A low U-factor means that less heat is lost through the window. A low U-factor is especially important in cold climates.

The SHGC measures the rate of heat gain through a product. A low SHGC means that less heat is transmitted through the window. A low SHGC is particularly important in hot climates.

How to sort out all of this data? Energy Star is a government program that certifies many different products for their energy efficiency. Their residential window certifications are based on four climate zones. Buying Energy Star products provides an easy way to know what you're getting in terms of energy efficiency.

However, some products meet Energy Star requirements although they do not carry the Energy Star certification. The National Fenestration Rating Council (NFRC)provides U-factor and SHGC statistics on a sticker on many windows. Comparing a window's NFRC statistics to the Energy Star requirements can help you find an energy-efficient window at a lower price.

Remember to check the Database of State Incentives for Renewables & Efficiency to see if any tax credits for energy efficient doors and windows are available in your area. The Energy Star website also includes information about federal tax credits.

There is more to selecting windows and doors than statistical comparisons. Beautiful doors, windows and window coverings can make a room. Selecting their materials, style, shapes and colors is the fun part. Keep that in mind when you're wading through the acronyms and numbers.

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Article is reprinted courtesy of The New Southwest (formerly Tucson Green Times).


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