Radon in Real Estate: What Home Buyers and Sellers Need to Know

Why Radon Derails Real Estate Deals

Radon testing has become standard in most U.S. real estate transactions — particularly in high-radon states like Iowa, Pennsylvania, Colorado, Minnesota, Ohio, and Illinois. When a buyer's test comes back above 4 pCi/L (the EPA action level), it triggers a contingency that can delay or kill a deal.

The good news: radon mitigation is a solved problem. A certified mitigator can typically reduce levels below 4 pCi/L in a single-day installation. The challenge is knowing who to call, how fast they can schedule, and what documentation to request.

For Sellers

Test Before Listing

In high-radon states, testing before listing gives you control. If levels are elevated, you have time to mitigate before buyers see the problem. An existing, working mitigation system is a selling point — not a liability.

Buyers in markets like Denver, Minneapolis, Columbus, and Philadelphia specifically look for homes with existing mitigation systems. A mitigated home closes faster and for closer to asking price.

Cost: Short-term charcoal test kits run $17–$25 from certified labs. Results in 3–7 days.

Pre-listing mitigation: $800–$2,500 for a standard slab or basement job. Less than a typical price reduction.

Disclosure Requirements

Radon disclosure requirements vary by state. Most states with significant radon issues (Iowa, Pennsylvania, Colorado, Minnesota, Illinois, Indiana) require sellers to disclose known radon test results. Some require disclosure if a mitigation system exists.

Check your state's specific requirements with a real estate attorney or your state health department's radon program. When in doubt, disclose — undisclosed radon issues are a source of post-closing litigation.

If You Have an Existing Mitigation System

Provide the buyer with:

• The original installation report
• The fan model and any service records
• The most recent radon test result (ideally a long-term alpha track test)
• The location of the manometer and what a normal reading looks like

A system that's been maintained and recently tested is a strong selling point.

For Buyers

Test Every Home — Regardless of State

Radon doesn't respect state averages. A home in Florida (typically low risk) can test above 4 pCi/L based on local geology. A home in Iowa might test low if it was built on different soil. The only way to know is to test the specific home.

Request a radon contingency in your offer. This is standard in most high-radon states. It gives you the right to negotiate mitigation or walk away if levels are elevated.

Understanding Your Test Results

• Below 2 pCi/L: Low risk. No action needed.
• 2–4 pCi/L: Elevated. EPA recommends considering mitigation, especially for long-term occupancy.
• 4 pCi/L and above: EPA action level. Negotiate mitigation as a condition of closing.
• 10+ pCi/L: High priority. Require mitigation before closing, not after.

Who Pays for Mitigation?

It's negotiable. Common arrangements:

• Seller-paid pre-closing: Seller installs the system, provides test results confirming it works.
• Closing cost credit: Seller provides a credit for the buyer to arrange mitigation after closing. (Less ideal — you have less control over contractor selection.)
• Price reduction: Buyer accepts elevated radon and negotiates a price reduction to offset mitigation cost.

Mitigation typically costs $800–$2,500 for a slab or basement. In the context of a real estate transaction, this is a small number — negotiate accordingly.

Verifying the Mitigation Contractor

Always request the contractor's certification number and verify it before work starts:

• NRPP certified: verify at radonproficiency.org
• NRSB certified: verify at nrsb.org

An uncertified installer may void your home insurance coverage for radon-related issues in some states and won't meet local code requirements where permits are required.

RadonBase lists only NRPP and NRSB certified mitigators — every contractor's certification is pre-verified before publishing.

For Real Estate Agents

The most common mistake: recommending a contractor without checking their certification. "He's done good work for other clients" is not the same as "he holds a current NRPP mitigation certification."

What to keep on hand:

• The RadonBase URL for your state (example: /states/ohio) — you can pull it up in seconds when a client needs a verified mitigator
• The EPA action level (4 pCi/L) and what it means
• A rough sense of mitigation cost ($800–$2,500 for most residential jobs)

In transactions where radon comes up:

1. Confirm the testing company is using EPA-approved protocols (short-term test, closed-house conditions, lowest livable level)
2. If results are at or above 4 pCi/L, recommend 2–3 certified mitigators for competitive quotes
3. Request post-installation test results in writing before releasing the contingency

Find certified mitigators in your state →