Radon Testing & Mitigation

Frequently Asked Questions

How much does a radon mitigation system cost?

A residential system costs $800–$2,500 installed, with most homeowners paying about $1,200–$1,500 for standard sub-slab depressurisation. Crawl spaces run higher — $1,500–$3,000 — because a sealed membrane has to go down before anything can be depressurised. Budget separately for the running costs: $60–$180 a year in electricity, and a $500–$1,100 fan replacement every 5–10 years.

What radon level is dangerous?

EPA sets the action level at 4 pCi/L — fix the home at or above that figure. Between 2 and 4 pCi/L, EPA suggests considering mitigation, because no level of radon is known to be harmless. Below 2 pCi/L no action is generally recommended, though retesting every couple of years is sensible. For scale, the average outdoor level is about 0.4 pCi/L and the average US indoor level about 1.3 pCi/L.

Does my county's radon zone tell me whether my house has radon?

No. EPA classifies all 3,142 US counties into Zone 1 (predicted above 4 pCi/L), Zone 2 (2–4) and Zone 3 (below 2), which is useful for codes and for knowing whether to prioritise testing. It cannot predict an individual building. Two homes on the same street routinely test very differently, because the result depends on the specific soil, foundation and ventilation beneath that house. Elevated homes have been found in every zone, including Zone 3.

Does crawl space encapsulation reduce radon?

Partly, and it is frequently oversold on this point. A sealed liner blocks the easiest path for soil gas and sealed crawl spaces do test lower, but the liner also traps gas beneath it. Actual mitigation needs a vent pipe running under the liner to a fan that exhausts above the roofline. Test before encapsulating, and if levels are elevated have the mitigation designed into the job rather than bolted on afterwards. Retest after any encapsulation — the previous result no longer applies.