What is Radon Mitigation?
Radon mitigation is the process of reducing elevated radon gas concentrations in buildings to safe levels. Radon is a naturally occurring radioactive gas produced by the decay of uranium in soil and rock. It is colorless, odorless, and tasteless -- making it undetectable without specific testing. Radon enters buildings through foundation cracks, gaps around pipes, construction joints, and any openings where the foundation contacts soil. It is the second leading cause of lung cancer in the United States (after smoking), responsible for an estimated 21,000 deaths annually according to the EPA. The EPA recommends mitigation when indoor radon levels exceed 4.0 picocuries per liter (pCi/L). Approximately 1 in 15 U.S. homes exceeds this threshold.
Testing
Radon testing is the only way to know whether a building has elevated levels. Short-term tests (2-7 days) cost $150-$300 when performed by a professional, or $10-$30 for mail-in DIY kits available at hardware stores. Short-term tests provide a snapshot and are commonly used during real estate transactions. Long-term tests (90+ days) provide a more accurate annual average reading and are preferred for existing homeowners. Most buyers in radon-prone areas (the upper Midwest, Appalachian region, and mountain states have the highest concentrations) request radon testing as part of the home inspection.
Mitigation systems
Sub-slab depressurization (SSD) is the most common and effective system. A PVC pipe is routed through the foundation slab into the gravel bed beneath, connected to an inline fan that creates negative pressure under the slab, drawing radon gas up through the pipe and venting it above the roofline where it dissipates harmlessly. SSD systems reduce indoor radon levels by 90% or more. Installation costs $800-$2,500, with most residential systems at $1,000-$1,500. The fan uses about $50-$100 of electricity per year, and the system lasts 15-25 years with minimal maintenance beyond periodic fan replacement.
Other approaches include sub-membrane depressurization for crawlspaces (a heavy plastic sheet is sealed over the soil with a pipe and fan pulling radon from beneath), heat recovery ventilators (HRVs) that increase ventilation while recovering energy, and sealing foundation cracks as a supplementary measure. Sealing alone is not sufficient -- active depressurization is needed for reliable reduction.
Real estate implications
Elevated radon is a negotiation point, not a deal killer. In radon-prone markets, buyers routinely request mitigation as a closing condition, and sellers who have already mitigated avoid this friction entirely. For investors, proactively installing mitigation ($1,000-$1,500) removes an objection that could delay or kill a sale worth tens of thousands of dollars. It also demonstrates that the property has been professionally evaluated and addressed, building buyer confidence.
Landlords with rental properties in high-radon areas should test and mitigate proactively. Several states now require landlords to test for radon and disclose results to tenants. Beyond legal requirements, a radon-related health claim from a tenant is a significant liability exposure. Always test before purchasing, mitigate if levels exceed 4.0 pCi/L, and disclose both test results and installed mitigation systems to all buyers and tenants.