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Re: Trying to keep cool



Around here most homes have air conditioning, but many homes also have "whole house fans." I have used a whole house fan for 20 years.

The fan is in the second-floor hallway ceiling and pulls air from the house, into the attic area, and out through attic vents. It's the same idea as a bathroom vent or a kitchen vent, except much bigger. Off the top of my head I can easily name a dozen people in my community who I know have similar set-ups.

Once the outside air temperature drops below the inside air temperature you open windows and turn on the fan. We open the windows only about 6 to 12 inches throughout the house, so we get a fairly rapid airflow into each room to help stir up the air. We can run the fan all night if we want. It has two speeds. High speed is fairly noisy, but low speed is very quiet. It is also on a timer that we sometimes use.

In theory you run the fan at night and cool the house into the 60s, then in the morning you shut the windows, pull the blinds on the sunny side of the house, and hope the thermal mass of the house keeps it fairly cool during the day. My house is old and has thick brick walls. If I can get everything down to 68F, then the inside will go up to about 78F on sunny days with temperatures in the mid-to-high 80s.

However, we have been having a lot of 95 degree days, high humidity, and with that combination the outside air temperature won't necessarily drop below 75F at night. We've had some nights where it barely gets below 80. With high humidity and warm nights the fan situation is not a good substitute for air conditioning.

I do have air conditioning. Over the last 20 years we have found that the whole house fan works quite well in September and October when nights are dry and cool. It sometimes works in April and May if it is not too humid. From June through August we rarely use the fan and rely on air conditioning simply because it is too humid and not cool enough at night. In a drier climate a whole house fan ought to work great.

Anyway, to answer the specific questions, the accepted procedure is to use a fan to exhaust air from the ceiling on the highest floor, and bring in fresh air through the windows. The house is then shut up during the day. That's the theory.


Michael D. Edmiston, Ph.D. Phone/voice-mail: 419-358-3270
Professor of Chemistry & Physics FAX: 419-358-3323
Chairman, Science Department E-Mail edmiston@bluffton.edu
Bluffton College
280 West College Avenue
Bluffton, OH 45817