No single law decides who pays for radon mitigation. In a home sale, the buyer and seller negotiate it as part of the purchase agreement. In a rental, the landlord almost always pays under the duty to keep the unit habitable. In a newly built home, the builder may owe the fix under local code or warranty. A typical system runs about $800 to $1,700 for a single-family home, though complex installations can run higher, so the real question is usually who absorbs a four-figure bill rather than who can afford it.
Home Sales: A Negotiated Expense
There is no federal rule putting radon mitigation on the seller. The cost is a negotiation inside the purchase contract, and leverage shifts with the market, the test results, and how badly each side wants the deal to close.
The Inspection Contingency Is Where Most Deals Settle
Most buyers write a radon inspection contingency into their offer. If testing comes back at or above the EPA’s action level of 4 pCi/L, the buyer can ask the seller to install a mitigation system, cut the price, or give a closing credit to cover the work.1U.S. Environmental Protection Agency. What Is EPA’s Action Level for Radon and What Does It Mean? This is where the cost usually lands on the seller in practice. A seller staring at a dead deal over a $1,200 system tends to agree to the repair rather than start over with a new buyer.
Buyers in hot markets sometimes waive the radon contingency to make their offer stronger. If the home later tests high, that cost is yours alone.
Escrow Holdbacks When the Work Can’t Finish Before Closing
When a mitigation system cannot be installed before closing, the parties can set up an escrow holdback. A slice of the sale proceeds stays in escrow until the work is done and a post-installation test confirms levels have dropped below 4 pCi/L. The holdback usually equals the highest contractor estimate plus a buffer. Both sides sign the holdback terms, and funds release once the work passes.
Disclosure Laws Give Buyers Leverage
Roughly three dozen states require sellers to disclose known radon test results or hazards during a real estate transaction. Some states also require a written radon warning statement in the sales contract. The common thread is that a seller who has tested and knows the results has to share them.
A seller who hides known results runs real legal risk. Buyers who find out after closing can sue for the cost of mitigation, lost home value, and legal fees, and in some jurisdictions courts have awarded punitive damages where the concealment was deliberate. The practical takeaway for sellers: if you know about a problem, you are generally better off fixing it than hoping it stays buried.
Rental Properties: The Landlord Pays
The implied warranty of habitability, recognized in most states, obligates landlords to keep rental units safe and fit for human habitation. That duty applies even when the lease is silent on repairs or environmental hazards. Elevated radon is an indoor air quality hazard that can render a unit unfit, so the mitigation bill falls on the property owner in most situations.
What a Tenant Can Do If the Landlord Refuses
Tenants can run a radon test themselves or ask the landlord to arrange professional testing.2U.S. Environmental Protection Agency. A Radon Guide for Tenants If results come in at or above 4 pCi/L, notify the landlord in writing and request mitigation. The EPA recommends confirming the first result with a second test before demanding action.
If the landlord stalls or refuses, state law may let a tenant withhold rent, hire a contractor and deduct the cost from rent, or break the lease without penalty because the unit is uninhabitable. Reporting the hazard to a local building or health inspector often speeds things up.
HUD-Assisted Multifamily Housing
For multifamily projects that receive HUD funding or insurance, radon testing and mitigation are eligible program costs. HUD policy requires radon to be considered in the environmental review for covered projects, and when testing finds levels at or above 4 pCi/L, the project must include a mitigation plan with post-installation testing and ongoing maintenance.3U.S. Department of Housing and Urban Development. CPD Notice on Departmental Policy for Addressing Radon in the Environmental Review Process Landlords of these properties absorb the cost into the project budget rather than passing it to tenants.
New Construction: When the Builder Is Responsible
Builders in about 30 states operate under some form of radon-resistant new construction (RRNC) code, though scope varies. Seven states apply RRNC codes statewide to designated areas, nineteen have local jurisdictions with their own requirements, and four have statewide codes that localities must adopt individually. The International Residential Code addresses radon control in Appendix F, and the EPA points builders to ANSI/AARST standards for radon-resistant techniques.4U.S. Environmental Protection Agency. Building Codes and Standards for Radon-Resistant New Construction (RRNC)
Many new homes are built with a passive radon system: a gravel layer under the slab, polyethylene sheeting, sealed foundation cracks, and a vent pipe running through the roof. Passive systems reduce indoor radon by roughly 50 percent on average. When that is not enough, an electric fan is added to make the system active.5U.S. Environmental Protection Agency. How to Address Radon When Building a New Home
If a new home tests at or above 4 pCi/L shortly after completion, the builder is often responsible for upgrading the passive system to an active one. How strong that claim is depends on whether local code required RRNC features, whether the builder’s contract or warranty covers environmental performance, and how soon after closing you tested. Homes still inside a one- or two-year builder warranty for mechanical and structural items generally have the strongest footing. Check the warranty documents for language on radon systems or indoor air quality.
Your best leverage is before closing. Test during the final walkthrough. If results come in high, negotiate the fan upgrade as a condition of closing rather than opening a warranty dispute later. A builder would usually rather install a $300 fan at closing than argue about it six months in.
If You End Up Paying
Sometimes the negotiation does not go your way, you discover the problem after closing, or you own the home outright and there is no one else to pay. A few avenues can help.
USDA Section 504 Loans and Grants
The USDA Single Family Housing Repair program offers loans up to $40,000 and grants up to $10,000 for very low-income homeowners in rural areas. The money can be used to remove health and safety hazards, which can include radon mitigation.6USDA Rural Development. Single Family Housing Repair Loans and Grants Grants are limited to homeowners aged 62 or older. Income limits are set by county, and you must be unable to obtain affordable credit elsewhere.
State Radon Programs
The EPA funds state and tribal radon programs through the State Indoor Radon Grant (SIRG) program, but those federal dollars do not go directly to individual homeowners. By law, SIRG money supports state-level outreach, testing initiatives, and program administration only.7U.S. Environmental Protection Agency. State and Tribal Indoor Radon Grants (SIRG) Program and Resources Some states use their own funds to offer low-interest loans or limited grants for mitigation, particularly for low-income households. Your state radon office, listed on the EPA’s website, can tell you what is currently available.
Homeowners Insurance Will Not Cover It
Standard homeowners insurance does not pay for radon mitigation. Policies cover sudden and accidental events like fires and burst pipes, not the gradual accumulation of a naturally occurring soil gas. Buyers who assume their policy will help after they discover high levels post-closing are generally disappointed.
Tax Treatment
Radon mitigation is generally not deductible as a medical expense. IRS Publication 502 defines deductible medical expenses to include “mitigation” of disease, but the IRS draws a line between treating a diagnosed condition and taking preventive measures against a general health risk, and radon mitigation falls on the preventive side for most taxpayers.8Internal Revenue Service. Publication 502, Medical and Dental Expenses
The practical tax benefit is adding the cost to your home’s cost basis. A higher basis reduces your taxable gain when you sell. Keep the contractor invoices. If you are near the capital gains exclusion limit, the adjustment can be worth real money at sale.