My crawlspace has high humidity and a musty odor. Since it is now warm and sunny outside, I want to vent it out.
The idea is to put a 8-inch centrifugal duct fan in the middle of the crawlspace and connect a flex duct from the fan's output to one of the crawlspace vents.
So if there are 10 crawlspace vents, 9 will be sucking air and one blowing air. If this creates a slight negative pressure in the crawlspace that would be even better; it would counter the tendency for crawlspace odor to migrate into the living are.
Question is how best to connect a 8-inch round flex duct to a rectangular crawlspace vent (about 16-inch by 7 inch inside dimension). I don't think there is a "round duct to crawlspace vent adapter".
Also, the crawlspace wall is concrete so it's not easy to attach anything to the wall.