Today's
TECHNOLOGY AND YOU

Q: I want to install a whole-house fan to use in the evenings and on milder days. Will using one instead of air-conditioning save much electricity overall? What are the best designs and features to get? - U. G.

A: Running a whole-house fan offers many benefits over continuous air-conditioning. A whole-house fan uses much less electricity. Whereas a typical central air conditioner draws more than 3,000 watts, most whole-house fans draw less than 600 watts. Depending on how often you use it, the overall electricity savings is often more than 50 percent and provides a good payback on the investment.

Many people also prefer to operate a whole-house fan in the evening to improve indoor air quality. With central air conditioning alone, the air in energy efficient homes gets stale and can actually become unhealthy. A reasonable combination of central air conditioning and whole-house fan use can provide fresh air while still minimizing the problems of high humidity. Whole-house fans cool a house and improve comfort in three basic ways. First, during times when the outdoor temperature is cooler (usually in the evening and early morning), they draw in fresh air to cool your house. All of the walls, furniture, cabinets, etc. cool down too, so they slow and reduce the natural indoor temperature rise the following day.

Second, the breeze created throughout the house makes you feel cooler and reduces that clammy feeling.

Third, since the air from inside the house 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 into the house well into the evening.

Although most whole-house fans look similar, there are major differences that affect comfort, sound levels, convenience and overall year-round efficiency. The type of controls affects comfort and convenience the most. Select a model with solid-state true variable-speed controls and a 12-hour timer.

Check sound-deadening, features on all the models. These features may be listed on the carton or you can inspect a floor sample. The motor should be mounted in rubber grommets to isolate vibrations from the frame. Some also use a hard rubber fan hub to reduce noise levels. An additional 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. On a direct-drive design, the fan blades attach directly to the motor shaft. The motor is mounted on supports in the center of the fan opening in the ceiling.

Direct-drive fans work well in small to medium-size houses. Many fit perfectly between the joints without any cutting for simple installation. For the easiest installation, choose a model with built-in louver shutters attached to the bottom. These block air leakage when the fan is not running.

Tamarack makes an easy-to-install double direct-drive fan design. It has

James Dulley is a mechanical engineer who writes on a wide variety of energy and utility topics. His column appears in a large number of daily newspapers.

Copyright 1996 James Dulley

18 ILLINOIS COUNTRY LIVING SEPTEMBER 1997

super-efficient R-22 insulated shutters above it that open automatically when the fan starts. By using two small fans side-by-side in the one frame, it fits snugly between joists on 16-inch centers without cutting.

For a larger house and for extra quiet operation, a belt-drive design is preferred. The motor is mounted on a corner of the frame. This positions it out of the direct air flow. These also use steeply pitched blades that turn slower than with a direct-drive model. This reduces noise and allows for greater air flow capacities (as high as 8,800 cubic feet per minute cfm).

For someone who wants ventilation at night and likes a closed bedroom door for security or privacy, you should install a new mini one-room fan by Kool-O-Matic. It is only 14 inches in diameter and has a one-foot-high outlet duct. This allows you to pack attic insulation high around it for efficiency.

It is important to select the proper size whole-house fan and to make sure that there is enough exhaust attic vent area. Generally, a 1,600 sq. ft. house needs a 4,800-cfm fan. A 2,400 sq. ft. house needs a 7,200-cfm fan. In a large house or sprawling ranch, install two smaller fans instead of one large one. Divide the total fan cfm rating by 750 to determine the required attic exhaust vent area in square feet.

Write for (or instant download -www.dulley.com) Utility Bills Update No. 880 - a buyer's guide of 20 whole-house fan. It lists drive types, sizes, cfm air flow capacities, comfort features, installation instructions and charts of recommended fan sizes and attic vent area. Please include $2 (checks payable to Jim Dulley) and a business-size SASE, to James Dulley, Illinois Country Living, P.O. Box 3787, Springfield, IL 62708-3787.

20 ILLINOIS COUNTRY LIVING SEPTEMBER 1997