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What is the best way to insulate the floor above a dirt crawl space?

nscc | Posted in General Questions on

This is in a cold climate and the crawl space is unheated.

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  1. Riversong | | #1

    First, there should be a well-sealed vapor barrier on the dirt floor, taped or caulked to the walls and around any penetrations. All penetrations between crawl space and conditioned space need to be sealed as well.

    Then you need a moisture tolerant insulation that will effectively decouple the floor framing from the radiant ground temperature and moisture. This would require rigid foil-faced polyisocyanurate foam board or sprayed closed-cell urethane foam that fully encapsulates the floor joists.

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