Step 2 · Seal Air Leaks

Inspect the crawl space walls and the rim joist (the perimeter of the floor structure where it rests on the foundation) for any air leaks. These can be gaps around pipes, wiring, vents, or where the foundation meets the wood framing. Seal these leaks using caulk or spray foam insulation. Pay close attention to the sill plate and any cracks in the foundation walls.