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Whole house fan draws in fresh air

Question: I am considering installing a whole house fan to use in the evening instead of my air conditioner. Will using one really save much electricity overall? What is the best design and features to get? _ U.G.

Answer: Running a whole house fan uses much less electricity than a central air conditioner. Depending on the weather and the number of cooler evenings, the overall electricity savings often ranges from 25 to 50 percent.

Many people prefer operating a whole house fan in the evening in order to get some fresh air into the house. With air-conditioning alone, the air in some newer efficient homes gets stale and can actually become unhealthy.

Whole house fans cool the house and improve comfort in three ways. First, during times when the outdoor temperature is cooler (usually in the evening), drawing in fresh air cools down your house.

Second, the breeze created throughout the house makes you feel cooler. Third, since the air is exhausted into the attic, the attic temperature is lowered significantly. A roof can reach 150 degrees in the afternoon. This heat is stored in the attic material and radiates down well into the evening.

Although all whole house fans look similar, there are major differences among them. The type of controls effects comfort and convenience. Solid-state true variable speed controls and 12-hour timers are a plus.

Check sound-deadening features. The motor should be mounted in rubber grommets to be vibration-isolated from the frame. A hard rubber fan hub also reduces noise levels. A sound-absorbing shroud, made of special chemically-treated materials, reduces the noise from the air flow.

The two basic designs of whole house fans are direct drive and belt drive. Direct-drive fans have the fan blade attached directly to the motor. The motor is mounted in the center of the fan opening.

Direct-drive fans work well in small to medium-size houses. Many fit perfectly between the joints without any cutting for simple installation.

For a larger house and for more quiet operation, a belt-drive design is best. By using pulleys with the motor offset on the fan corner, the fan blades turn slower. This reduces noise and allows for a steeper blade pitch. Air flow rates are as high as 8,800 cubic feet per minute (cfm).

For those who close bedroom doors for security or privacy, install a new mini one-room fan. It is only 14 inches in diameter and the outlet duct is one foot high. This allows you to pack attic insulation high around it.

Write for Update Bulletin No. 880 showing a buyer's guide of 20 whole house fans listing drive types, sizes, cfm air flow capacities, comfort features, installation instructions and charts of recommended fan sizes and attic exhaust vent areas. Please include $2 and a business-size SASE.

Freezer costs

Question: I have a fairly large side-by-side refrigerator/freezer. I tend to buy a lot of food on sale. To make the frozen foods last longer, I plan to set my freezer temperature lower. Will this use much more electricity? _ S.S.

Answer: Lowering the freezer temperature by 5 degrees can increase the electricity usage by about 20 percent. This can amount to more than 130 extra kilowatt-hours of electricity used each year.

You should set your freezer temperature to the manufacturer's or your local health department's recommendation. Check it with a good outdoor thermometer.

James Dulley is an engineer. Send questions to James Dulley, the Sensible Home, the Times, 6906 Royalgreen Drive, Cincinnati, OH 45244.

His new 328-page book, $en$ible Home, compiles 81 of his most popular columns and Update Bulletins. Included are 600 manufacturers of super-efficient products, 400 manufacturers of money-saving household and healthy environmental (anti-allergy) products, 32 low-cost do-it-yourself projects and super-efficient house construction. Order directly from James Dulley for $15.95 (includes delivery and postage) with check or money order made payable to James Dulley. Mail to James Dulley, New Book, 6906 Royalgreen Drive, Cincinnati, OH 45244.

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