Crawlspace radon mitigation

The method is called sub-membrane depressurization. A durable polyethylene vapor barrier is sealed across the entire crawlspace floor and to the walls. A radon fan then draws air from the space beneath that membrane and vents it above the roofline — the same principle as a slab system, but the sealed membrane takes the place of the concrete slab.

Done right, it both lowers radon and cuts soil moisture coming up into the home — a common side benefit in older Colorado crawlspace houses. As with any system, we include a post-install re-test to confirm levels dropped below the EPA action level of 4 pCi/L.

This is the right system for homes built over a crawlspace rather than a slab or full basement. Because it involves more material and labor than a single slab suction point, crawlspace mitigation runs $2,000–$5,000, depending on crawlspace size, access, and condition. Homes with both a basement and a crawlspace usually need a multi-foundation system.

See the full mitigation overview for how this compares to a standard sub-slab system, or test your home first.