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Shades Of Savings

I have always liked the appearance of window awnings. The salesman told me they can also save energy. Do they really save much energy, and what choices are best?
—William B.

Installing window awnings can reduce the cooling energy usage in your home. There are other benefits, such as reduced fading of furniture, drapes, and carpeting, as well as protection of primary windows from the sun and severe weather.

Make sure the awnings are sturdy, to stand up against Kentucky wind storms.

Awning energy savings are greatest during the afternoon when the sun is most intense.

There are many window awning options available. The first decision to make is whether you want fixed or adjustable awnings. Both are equally effective during the summer to reduce your peak electricity usage in mid-afternoon. The advantage of adjustable awnings is that the level of shading can be changed throughout the day and various seasons.

Adjustable fabric awnings offer better protection from severe weather because some can be lowered to be almost flat over the window opening. They can also be raised to expose most of the window glass. The maximum projection from the wall for an adjustable aluminum awning is fixed by the frame and the down arm length. To open them, the aluminum awning slats roll up above the frame and the hinged arms swing upward. The advantage of aluminum is its strength and its resistance to degradation from the sun.

Sideless awning designs, called Venetian awnings, are effective for true-south facing windows because the most intense sun’s rays come from overhead. Actually, just a short flat board over the window, such as a large roof overhang, is effective at blocking the sun over these windows. If you need to block the late afternoon sun at those south-facing windows, install hood-style awnings with sides. For casement windows, hip-style awnings provide clearance for the window sash to swing open outward.

Proper sizing (projection length from the house wall) of window awnings is important for blocking the summer sun and for allowing the winter sun to shine through the windows for free passive solar heating. This is particularly true if you install fixed awnings, instead of adjustable ones, because their shading cannot be changed. The orientation of the window to the sun also affects the proper awning sizing because the sun is lower in the sky during early morning and late afternoon.

If you still remember some of your high school geometry, you should be able to calculate the size of awning needed for various windows in your house. The latitude angle for your area determines how high the sun is in the sky and its angle of incidence on your windows. The sun’s height also varies throughout the day and seasons. You can find the sun location for various regions, seasons, and times of day in most basic solar energy books. If you are not a math whiz, make some test awnings with cardboard to determine the proper size.

The following companies offer window/door awnings: Awntech, (800) 200-5997, www.awntech.com; Craft-Bilt, (800) 422- 8577, www.craftbilt.com; Durasol Awnings, (888) 387-2765, www.durasol.com; Eastern Awning, (800) 445-4142, www.easternawning.com; and Try-Tech Industries, (866) 337-2381, www.try-tech.com.

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