I cut a 12x4 floor vent to the crawl space beneath the house. The other day it was 95*F outside, but the crawl space stayed 72*.
I also installed a 4" ceiling vent connected to a 200 CFM attic exhaust fan in the attic, while keeping the existing ceiling and low wall vents since I think I need them for furnace combustion.
Unfortunately, the weather dropped back to 70°F right after, so I haven't been able to test how well everything works yet.
I'm still considering whether to enlarge the floor vent, upgrade to a 6" attic duct, and/or switch to a 400 CFM fan.
(Excuse the mess in the photos, not done yet.)
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