Attic fans aren't for cooling attics. Ridge vents, and passive and powered roof vents, and turbines mounted in the roof surface can cool attics far more effici

Attic fans aren't for cooling attics. Ridge vents, and passive and powered roof vents, and turbines mounted in the roof surface can cool attics far more efficiently than attic fans which consume over 100 watts and must run continuously on summer days -- a very costly way to air out an attic. Though old houses often have attic fans, they weren't there to cool attics. That was the purpose of widowed attic gables or breathing slats under wood shingled roofs. Attic fans are there to cool the house interior, especially the hottest rooms on uppermost floors. That's why the intake of an attic fan is the highest point inside the house and not the lowest point inside the attic. Even then attic fans aren't intended to run for more than perhaps 30 minutes a day after sundown -- just long enough to replace the hot air inside the home with cool air from outside. To vent an attic, the ideal air flow is to intake cool dry outside air from along the attic soffet, pass it along the underside of the hot roof sheathing, and have it exit high where attic heat is at its peak. And do this passively without a powered fan if at all possible.