I have an attic fan on my house. It is a solar fan with a thermostat so that it will vent hot air in the summer when I want to cool the attic, but not in the winter when heat in the attic is positive for energy savings. Unfortunately the one I have is located on west side of the ridge so it only gets sun in the afternoons.
The Master Flow Green Machine Solar Powered Ridge Vent sits on the ridge. This has the advantage of being at the highest point so it takes out the hottest air as well as being in a position to get the maximum amount of sunlight.
I would consider this Green that saves Green…