Radon Testing and Mitigation
Test for radon; no levels above PCL 4 permitted. Install a passive or active mitigation system if needed. All new construction and all EPA Zone 1 homes require a system.
Spec
Applies uniformly from Certified upward.
Scope
Indoor radon levels throughout the dwelling, with emphasis on the lowest livable floor.
Requirements
- 01.
Perform a 48-hour minimum short-term radon test on the lowest livable level of the dwelling. Test must follow EPA protocol (closed-house conditions for 12 hours before + during test).
- 02.
If result is ≥ 4 pCi/L, install a radon mitigation system (passive or active sub-slab depressurization) and retest to confirm post-mitigation levels.
- 03.
All new construction in any climate must include a passive radon system (4" vertical riser from sub-slab to roof, capped or fan-assisted).
- 04.
All homes in EPA Zone 1 counties must include an active radon system regardless of initial test results.
Documentation
Evidence the inspector / Institute will need.
- 01.
Radon test report from a certified lab (NRPP or NRSB), with the test conditions, dates, and result in pCi/L.
- 02.
For mitigation: system design + photos showing the riser, fan (if active), and roof termination.
- 03.
Post-mitigation retest report.
Guidance
Why this is a Certified-level requirement
Radon is the #2 cause of lung cancer in the U.S. after smoking — and #1 among non-smokers. The EPA estimates ~21,000 deaths/year are attributable to radon exposure. Testing costs $25-$50; mitigation costs $800-$2,500. Both are dramatically cheaper than the health consequences of unaddressed exposure.
Resources
- EPA Radon Map (Zone 1, 2, 3) →
County-by-county classification of radon potential.
- NRPP — National Radon Proficiency Program →
Find a certified radon measurement or mitigation professional.
- EPA Citizen's Guide to Radon →
Background on health risks + testing protocol.
Note
Long-term radon tests (90+ days) are more accurate than 48-hour short-term tests. GHI accepts either for compliance, but for occupied homes with marginal short-term results (3.0-3.9 pCi/L), a follow-up long-term test is recommended.