Radon Mitigation Calculator

This calculator models what happens after you install a radon mitigation system, using the midpoint of each system's published reduction-efficiency range. Active soil depressurization (ASD) — a fan-powered pipe drawing gas from beneath the slab and venting it above the roofline — removes 80-99% of radon, so the calculator uses an 89.5% typical reduction; sub-membrane depressurization for crawl spaces runs 70-95%; a heat recovery ventilator, which simply dilutes indoor air rather than blocking the soil-gas source, only manages 25-50%; and sealing cracks alone, the weakest option, is 10-30%. Multiply your current reading by (1 − that efficiency) to get the estimated post-mitigation level, then the calculator checks it against the EPA's 4 pCi/L action level (from EPA's "A Citizen's Guide to Radon") and the World Health Organization's stricter 100 Bq/m³ reference level — about 2.7 pCi/L once converted at 37 Bq/m³ per pCi/L, from the WHO Handbook on Indoor Radon. Installation cost is a flat base fee plus a per-square-foot rate scaled to the foundation area, reflecting that ASD systems need more piping and a larger fan for bigger basements.

Health risk reduction uses the EPA's linear no-threshold model — radon risk scales directly with concentration with no safe floor — applying roughly a 0.008% annual excess lung-cancer risk per pCi/L reduced, expressed here per 1,000 people for readability. Keep in mind these are typical, not guaranteed, efficiencies: actual performance depends on soil permeability, slab cracks, and installation quality, so a post-mitigation retest is always the real verification, not this estimate. Foundation type is informational here — it doesn't independently shift the output — the system type you pick is what drives the numbers.