All attic fans are not created equal. Some vent out of the side of your attic (not so great). Some are mounted on the deck of your roof. (I’m not writing about “whole house fans” which are, usually, mounted in a hallway and pull air out of the house and fresh / cool air in through the windows.)
Four things to look for if you’re considering an attic fan:
1. power source: solar or electric (could require up to a 20A dedicated circuit depending on the motor current draw.
2. CFM: Cubic Feet per Minute — How much air the thing is going to move.
3. Ease of installation
4. Night-time Function
CFM, how much air you can move, is the first critical task of the fan. Solar fans don’t move nearly as much air (about 740 CFM) as a powered fan but they’re less expensive to install while they cost more. You can figure for a 2,000 square foot home to need two solar fans to get a 20 degree drop in attic temp.
Installation: a solar fan just requires a hole in the roof and some flashing. It turns on when it gets some sunlight, including the wintertime. A powered fan could be tied into an existing circuit or require its own circuit: a bit more pricy to install but these fans are, usually, less than $150 (and come with a thermostat) at Friedman’s while solar powered units can cost upwards of $700.
So, the tradeoffs are ease of installation versus cost and installation of the unit. Solar fans won’t move any air at night…so that’s another consideration. And, yes, we can install any of them.