Is it worth the savings in energy cost to install a gable fan for my attic?
I went up there and to install a bath fan and it was ridiculously hot. There are currently grated vents at each end of the attic, and grated vents about every 10-15 feet under the gutters. There is also about 1 ft of blown in insulation. I was thinking of installing a gable fan connected to a thermostat. If I were to do this, at what temperature should I set the thermostat? And should the fan blow air inward or outward? I live in Louisville, KY.
Gable vents are definitely worth the money but even more important are ridge vents (near the peak of the roof) There should be at least one for every 10 linear feet of roof. Ridge vents let hot air out like gable fans but don't require any electricity and also allow circulation year round which will prevent moisture build-up in the attic (bad for lumber and insulation).
The fan should blow out – you want the cool air coming in through the soffit vents (near gutters). The fan manufacture should have recommendations for temperature settings.
Be sure to have a qualified roofer do the ridge vent install – you don't want any leaks!
Hope that helps.