Using crawl space vents for soil gas/radon mitigation in an encapsulated crawl space
I’m planning on encapsulating my crawl space. For wall insulation, I’m considering doing the following:
1. putting a metal bug screen over the vents, leaving them open to vent
2. installing rigid foam (EPS with a vapor barrier on each side) over the vents, leaving a 1 inch air gap along the wall and ground
I’m thinking to do this for a few reasons:
1. the air gap will allow radon and soil gases to vent out
2. the air gap will allow the ground to dry to the outside
3. using rigid foam will prevent my walls, which seep water, from filling with water (versus spray foam), allowing water to run to my sump pit
My crawl space has a few inches of gravel throughout, which should help with the things above.
I’ve tested the radon levels in my home. They are low, 2 to 3 pCi/L. I’ve even tested in the crawl space; with the vents closed, vapor barrier on the ground, it’s only 4 to 5 pCi/L. So this venting would just be an extra safety measure. I’ll continue to monitor radon and odor levels and can add active soil gas mitigation later if needed.
I’m planning on air sealing all penetrations through the subfloor, so there shouldn’t be much stack effect air coming into the first floor.
Are there any reasons this would not work? I’m in the Nashville, TN area, climate zone 4A.
GBA Detail Library
A collection of one thousand construction details organized by climate and house part