Although they may be initially more expensive than single room a/c units whole house fans can save a lot on your electric bill and increase your green footprint.
Whenever the outside temperature drops below inside temps, open some screened windows and flip on the fan to pull cool, dry air through the house and exhaust hot air through your roof vents.
For a morning “pre-cool,” run your whole-house fan just before sunrise, then close the windows to seal in the cool air as the day warms up. In the evening when outside temps dip, turn on your fan to cool off the house, which takes about 20 minutes for a 2,500 sq. ft. house.
In general, whole-house fans are more effective in multi-story homes than single-level.
(You can find more house logic tips on the bottom right of this page)