Radon has become one of the most common issues in real estate transactions. As awareness grows and more states adopt disclosure laws, both buyers and sellers need to understand how radon affects the buying and selling process — and how to handle it when it comes up.
Whether you're buying your first home, selling a property, or representing clients as an agent, this guide covers everything from testing requirements and disclosure laws to negotiation strategies and the financial impact of radon on property values.
Why Radon Is a Big Deal in Real Estate
Radon is the second leading cause of lung cancer in the United States. The EPA estimates that 1 in 15 homes has radon levels at or above the action level of 4.0 pCi/L. That means in any given real estate market, roughly 7% of homes have a radon problem that needs to be addressed.
For buyers, discovering elevated radon during inspection is a significant health and financial concern. For sellers, undisclosed radon can lead to failed deals, price reductions, and in some states, legal liability. For agents, understanding radon is essential for guiding clients through one of the most common inspection findings.
The financial impact is real: a home with known elevated radon and no mitigation system can sell for $5,000 to $15,000 less than comparable homes, according to multiple real estate studies. Conversely, a home with a properly installed mitigation system is often viewed positively by buyers — it's one less thing to worry about.
Radon Disclosure Laws: What's Required?
There is no federal law requiring radon testing or disclosure in home sales. However, more than 37 states have enacted some form of radon legislation — ranging from mandatory disclosure of known radon levels to requirements for radon-resistant new construction.
⚠️ Common State Requirements
Disclosure of known radon levels: Many states require sellers to disclose any radon test results they have, even if the test was done years ago. Failing to disclose known elevated levels can result in legal liability after the sale.
Radon testing during transactions: Some states require or strongly recommend radon testing as part of the home inspection process. In Illinois, for example, disclosure is mandatory on the property disclosure form.
Radon-resistant new construction (RRNC): Several states and many local jurisdictions require new homes to be built with passive radon-resistant features — a gravel layer, plastic sheeting, sealed penetrations, and a pipe stub that can be activated with a fan if testing shows elevated levels.
Certified tester requirements: Some states require radon testing for real estate transactions to be performed by a state-certified or nationally-credentialed (NRPP/NRSB) radon measurement professional.
Even in states without specific radon laws, most standard real estate contracts allow buyers to test for radon during the inspection period. And in practice, radon testing has become so common that many buyers request it regardless of legal requirements.
States with Notable Radon Legislation
This is not a complete list. Check with your state radon office for specific requirements in your area.
For Home Buyers: What You Should Do
If you're buying a home, radon testing should be part of your due diligence — just like a home inspection, termite inspection, or title search. Here's a step-by-step approach:
Include radon testing in your inspection contingency
Your purchase agreement should include a radon testing contingency or at minimum allow radon testing during the inspection period. Most standard contracts already include this language.
Hire a certified professional
For real estate transactions, use a certified radon measurement professional — not a DIY kit. The tester should be certified through NRPP (National Radon Proficiency Program), NRSB (National Radon Safety Board), or your state's certification program. Results from a certified test are legally defensible and accepted by all parties.
Understand the test protocol
Real estate radon tests follow strict protocols: closed-house conditions for at least 12 hours before and throughout the 48-hour test, the continuous radon monitor (CRM) placed in the lowest livable area, and tamper-evident deployment. The tester sets up and retrieves the equipment.
Interpret the results
If results are below 4 pCi/L, no action is needed (though some buyers negotiate mitigation for levels between 2–4). If results are at or above 4 pCi/L, you have a legitimate basis to request mitigation — either performed by the seller before closing or as a credit toward the purchase price.
Negotiate based on results
If radon is elevated, common negotiation outcomes include: the seller installs a mitigation system before closing ($800–$2,500), the seller provides a credit at closing for the buyer to install mitigation, or the purchase price is reduced. Most sellers prefer to install the system themselves, as it's cheaper and faster than a credit.
For Home Sellers: How to Handle Radon Proactively
Many sellers are blindsided by radon during a transaction. A buyer's test comes back elevated, and suddenly the deal is at risk. The smart approach is to get ahead of it:
Test before listing
Spend $125–$275 on a professional test before your home goes on the market. If levels are low, you have proof to show buyers. If levels are elevated, you can mitigate before listing and market the home with a functioning radon system — which many buyers view as a positive feature.
Mitigate proactively if elevated
Installing a mitigation system costs $800–$2,500 and takes one day. Doing it before listing eliminates a common objection, prevents price negotiations after inspection, and allows you to include "radon mitigation system installed" in your listing — which is a selling point in high-radon areas.
Disclose honestly
If you have radon test results — whether current or past — disclose them. In 37+ states, failure to disclose known radon levels is a legal liability. Even in states without specific radon disclosure laws, concealing known environmental hazards can expose you to fraud claims after closing.
Keep documentation
If you've installed a mitigation system, keep all documentation: the installation invoice, post-mitigation test results, the contractor's certification, and any warranty information. Provide this to the buyer as part of the seller's disclosures.
Don't panic over elevated results
Radon is fixable. A $1,200 mitigation system is minor compared to the total value of a home sale. Sellers who address radon proactively almost always come out ahead compared to those who try to avoid the issue.
Radon Negotiation Strategies
When radon test results come back elevated during a transaction, negotiations usually follow one of these patterns:
| Approach | How It Works |
|---|---|
| Seller installs system | Seller hires contractor, system installed before closing, post-mitigation test confirms results |
| Seller credit at closing | Seller provides a credit (usually $1,000–$2,500) at closing for buyer to install system |
| Price reduction | Purchase price reduced to account for mitigation cost. Less common but sometimes preferred. |
| Split the cost | Buyer and seller each pay half. A compromise approach when neither party wants to bear full cost. |
| Escrow holdback | Funds held in escrow for mitigation to be completed after closing. Used when timing is tight. |
In most markets, the seller installing a mitigation system before closing is the preferred outcome for both parties. The buyer gets a working system with a warranty, and the seller controls the process and cost. Credits and price reductions tend to be inflated because buyers add a margin of safety.
How Radon Affects Property Value
The impact of radon on home values is nuanced. Here's what the research shows:
The key takeaway: radon mitigation is an investment that typically pays for itself in a real estate context. Sellers who mitigate proactively save money and sell faster. Buyers who insist on mitigation protect both their health and their investment.
For Real Estate Agents: Best Practices
As an agent, your job is to guide clients through radon issues without creating unnecessary fear or dismissing legitimate concerns. Here are best practices:
- Always recommend radon testing during the inspection period, even if the state doesn't require it. It protects your client and shields you from liability.
- Use certified testers only for transaction-related tests. DIY kits are not accepted and can create disputes.
- Understand your state's disclosure laws and ensure your clients comply. Failure to disclose is the most common source of radon-related legal issues in real estate.
- Frame radon as a solvable problem. Don't let elevated results kill a deal. Mitigation costs $800–$2,500 and takes a day — it's one of the cheapest and fastest inspection findings to resolve.
- Advise sellers to test before listing whenever possible. This avoids surprises, speeds up transactions, and puts the seller in a stronger negotiating position.
- Have radon contractor referrals ready. Being able to quickly connect clients with certified mitigation professionals keeps transactions on track.
Common Questions About Radon in Real Estate
Can I walk away from a deal because of radon?
Yes, if your contract includes a radon contingency or general inspection contingency. However, most buyers negotiate mitigation rather than walking away, since it's an inexpensive fix. Walking away over a $1,200 problem on a $300,000+ purchase is rarely the best financial decision.
Who pays for radon testing — the buyer or seller?
Traditionally, the buyer pays for radon testing during inspection ($150–$400), just as they pay for the home inspection. However, some sellers proactively test before listing to get ahead of the issue. In competitive markets, sellers may offer to cover the testing cost.
How fast can mitigation be installed if we're under contract?
Most mitigation systems can be installed in a single day. From scheduling to completion, expect 3–10 business days depending on contractor availability. Post-mitigation testing takes an additional 48 hours. In total, you're looking at 1–2 weeks to fully resolve a radon issue, which fits comfortably within most closing timelines.
Should I buy a house with high radon?
High radon levels alone are not a reason to avoid buying a home. It's a common, well-understood problem with a proven, affordable fix. What matters is that the radon is addressed before or shortly after closing. The far bigger concern would be a seller who refuses to address it — that's a red flag about the property and the transaction.
Does FHA or VA require radon testing?
FHA and VA do not require radon testing for loan approval. However, VA strongly recommends it, and some VA appraisers in high-radon areas may note the absence of testing. Regardless of loan type, radon testing is always recommended for the buyer's health and financial protection.
✅ The Bottom Line for Real Estate
Radon is one of the most common and most easily resolved issues in real estate transactions. Buyers should always test. Sellers should consider testing and mitigating before listing. Agents should treat radon as a routine, solvable finding — not a deal-breaker. With 37+ states requiring some form of disclosure and mitigation costing as little as $800, there's no reason for radon to derail a real estate transaction.