Sub-membrane depressurization is the crawl-space variant of mitigation. Our Cincinnati mitigators install a sealed vapor barrier across the crawl space floor and create suction beneath it to draw radon away. Often combined with encapsulation.
More detail
A typical Cincinnati crawl-space SMD install: clean the crawl space (remove debris, address standing water), install pier wraps where needed, lay a continuous 12-mil reinforced polyethylene barrier over the entire dirt floor and up the foundation walls 6-12 inches, seal all seams with butyl-rubber tape, seal the perimeter to the foundation, install a sub-membrane suction pipe drilled into the underlying soil, route the stack up through the home and out through the roof or upper exterior wall, mount the inline radon fan, and verify with a manometer. Total time: 1-2 days. Cost: $1,800-$3,500 for a typical 800-1,500 sqft crawl space, depending on access and existing moisture issues. SMD often pairs with crawl-space encapsulation for combined moisture-and-radon mitigation, especially in older Cincinnati homes near the Ohio River corridor where humidity loads are high. Cincinnati crawl-space cost factor: existing moisture conditions add scope. Crawl spaces with standing water need pump-out and vapor-barrier prep work before SMD can begin. Crawl spaces with prior fiberglass batting need that material removed and disposed of. Both add cost and time. Our team quotes SMD against the actual scope after on-site assessment, not against generic pricing.