Trying to stay ahead of summer this year. I have a dead area in my attic which would be conducive to heat gain. Its also right where a hvac system is. After pricing out solar fans and trying to snipe a few on ebay I built one myself. I bought a 30 watt pv panel on craigslist for $40, new 10" 12volt dc car radiator fan for $16 shipped, and a gravity roof vent for $20. The fan's tag says 80 watts. My 30 watt panel can make it scream. It seems the gravity vent restricts the flow somewhat. I could feel the air chop near the fan blades. I added a fan shroud made from a 12" duct start collar and it helped the fan draw more suction. Super easy way to use free power!
