Procedure: Vented to Unvented Crawlspace Conversions
Close off and seal exterior crawlspace vents against water and air.
Install 15 mil polyethylene sheet on the crawlspace floor and seal it to the exterior walls and all other upturns at the floor and at laps on the floor with acoustical sealant and tape.
Install rigid foam board on the exterior wall and attach with mechanical fasteners.
Tape all insulation joints with compatible sheathing tape to make airtight.
Install rigid foam board between floor joists at the rim joist. Size them to fit snugly between joists.
Install spray foam around all joints at the rim joist and seal to the wall insulation.
