My house is 112 years old. I was in my attic and soaking my shirt because it was 120° in there (I live in Florida). I thought how nice it’d be to get some fresh air in there. I thought it’d be even better if I could get that air from the (somewhat) cooler air in my crawlspace. Then I noticed the 4" cast iron pipe that was used to be the drain pipe for the house from 1915 through about 2000. The vent for that pipe runs through my attic and straight down to my crawlspace…unused and forgotten. So I cut the pipe and disconnected it from the roof and cut off and closed up any branches it had. I cut it and slapped a screen on it in the crawlspace. In the attic I put on an inline fan (6 watts) and a bit of duct to vaguely direct it around the attic. Early tests say my attic is about 7° cooler. Am I crazy?
Attic is vented but it does little good without a decent wind. Crawlspace is slightly cooler than outside ambient air, call it 85° in June. The same wind that would help the attic would also remove the cool from the crawlspace I think? Attic is insulated with old old blown fiberglass and then a layer of newer rolled fiberglass - not terrible insulation actually. Also the crawlspace is insulated from the house with spray foam insulation.