Insulate floor in closed crawlspace?

Old 10-02-19, 12:21 AM
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Insulate floor in closed crawlspace?

My house is a bit of an energy pig and I want to work on that. I am in NC and we have long hot/humid seasons. My crawl space is currently open vented style, sloping from about 3' to 6', made of concrete block with vents. The bottom floor of the house is insulted with 2x4 thick fiberglass batts in poor condition.There is a vapor barrier on the ground but it isn't installed very well. My air handler for the heat pump system and ducts are mounted under here.

Right now the crawl space is very humid (~85%) and a bit cooler than outside temps. The air handler and ducts sweat heavily while the A/C is on. I would like to close in the crawl space and make it a semi conditioned space. I would install a combination of heavy plastic liners and a concrete floor in about half the space with a vapor barrier underneath. The walls would get insulated with either ridgid foam, or built out with 2x6 and filled with fiberglass batts.

My question is should I insulate the floor of the crawl space? It seems like the ground is warmer in the winter, and colder in the summer, which is what I want. Would insulation really make a big difference? It would not be cheap to cover about 1300 sq ft in insulation.

The big thing is adding a dehumidifier and keeping it below 70% humidity.

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