QUESTION: I have always liked the appearance of window awnings. The salesman told me installing them can also save a lot of energy. Do they really save much energy, and what awning choices are best?ANSWER: Installing window awnings can significantly reduce summertime cooling electricity usage. This reduction results from blocking direct radiant heat from the sun through windows. Studies by the University of Minnesota found installing window awnings can reduce cooling energy needs by 21 percent in Phoenix, 17 percent in St. Louis and 24 percent in Boston.Another advantage of awning energy savings is it is greatest during the hottest hours of the afternoon when the sun is most intense. This reduces the peak electricity load for the utility company's electric generation, so there is less chance of brownouts and other problems from excessive electricity demand.There are many window awning options available. The first decision to make is if you want fixed or adjustable awnings. Both are equally effective to reduce your electricity usage during mid-afternoon. The advantage of adjustable awnings is the level of shading can be changed throughout the day and seasons.Adjustable fabric awnings offer better protection from severe weather because some can be lowered to be almost flat over the window opening.They also can be raised to nearly totally expose the window glass. The maximum projection from the wall for an adjustable aluminum awning is fixed by the frame and the down arm length.Sideless awning designs, called Venetian awnings, are effective for true south-facing windows because the most intense sun's rays come from nearly directly overhead. Actually, just a relatively short flat board over the window, such a large roof overhang, is effective at blocking the sun over these windows.If you also 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 for natural ventilation.Proper sizing (projection length from the house wall) of window awnings is important both 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.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. If you are not a math wiz, just 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.

QUESTION: My house is about 1James Dulley has a degree in mechanical engineering. His column is published in more than 400 newspapers.Send inquiries to James Dulley, Butler Eagle, 6906 Royalgreen Drive, Cincinnati, OH 45244 or visit www.dulley.com.