Radon is one of the few home hazards you can’t see, smell or taste, which is exactly why it gets overlooked. Here in south central Wisconsin, it’s something every buyer should think about before closing. This guide explains how radon testing in Madison, WI works during a home purchase, what the results mean, and how to fit a test into your inspection timeline.
What Is Radon?
Radon is a naturally occurring radioactive gas that forms as uranium in soil and rock breaks down. It moves up through the ground and can enter a home through foundation cracks, gaps around pipes, sump pits, floor drains and other openings. Once inside, it can build up, especially in lower levels.
The U.S. EPA identifies radon as the second leading cause of lung cancer in the United States, after smoking. Testing is the only way to know your levels.
Why Radon Matters in Wisconsin
Wisconsin sits in one of the EPA’s highest radon zones, and many homes in our area test above the EPA’s recommended action level of 4 picocuries per liter (pCi/L). Radon levels can vary a lot from one house to the next, even on the same street. A neighbor’s result doesn’t tell you anything reliable about the home you’re buying.
Newer homes aren’t automatically safe, and neither are homes without a basement. Any home in contact with the ground can have elevated radon.
How Radon Testing Works During a Home Purchase
For real estate transactions, radon is usually measured with a short-term test that runs for at least 48 hours. Here’s how it typically goes with HomeStart:
- Placement: We set up professional, EPA-approved testing equipment in the lowest livable level of the home.
- Closed-house conditions: Windows and exterior doors should stay closed during the test, apart from normal entry and exit, so the results reflect real living conditions.
- Retrieval and reporting: We collect the equipment and deliver a report with the readings, clear results, and recommendations if mitigation is needed.
Because the test needs time to run, it’s best to schedule it at the same time as your home inspection. That way your results arrive within your inspection window.
Understanding Your Results
- Below 4 pCi/L: Below the EPA action level. The EPA notes that no level of radon is completely risk-free, and some homeowners still choose to reduce levels between 2 and 4 pCi/L.
- 4 pCi/L or higher: The EPA recommends fixing the home. That usually means installing a radon mitigation system.
An elevated result doesn’t have to end your deal. Radon can usually be reduced, and many buyers negotiate for the seller to install a system or provide a credit. Your agent can help you decide which approach makes sense.
What Is Radon Mitigation?
The most common approach is a vent pipe and fan system that pulls radon from beneath the foundation and exhausts it above the roofline. Sealing cracks and openings can help but usually isn’t enough by itself. After a system is installed, the home should be retested to confirm it’s working.
HomeStart doesn’t perform mitigation. We’re a third-party tester, so our results and recommendations aren’t tied to selling you a fix. If you need a system, use a qualified mitigation contractor.
Tips for Accurate Radon Results
- Let the seller and listing agent know a radon test is scheduled so closed-house conditions are kept.
- Don’t move, unplug or cover the testing equipment.
- Avoid running whole-house fans or opening windows during the test.
- If the home already has a mitigation system, make sure the fan is running and ask for any past test results.
Pairing Radon With Other Inspections
Many Dane County buyers bundle radon testing with other services so everything happens on one schedule. Common pairings include a sewer scope for older homes, well and septic inspections for rural properties, and a WDO inspection when a lender asks for one. If you’re also worried about dampness below grade, see our guide to the signs of mold when buying a house.
Radon Testing Across the Madison Area
HomeStart inspects homes across the Madison area every day. Learn more about our Madison home inspections and Middleton home inspections, or see our pages for Sun Prairie, Fitchburg and Verona.
Related reading: How to Choose a Home Inspection in Madison, WI and What to Expect During a Home Inspection in Wisconsin.
Common Radon Questions From Madison Buyers
“The seller already tested. Do I need to retest?” Ask how old the test is, who performed it, and whether the home has changed since then, for example a finished basement, a new HVAC system or foundation work. Radon levels can change over time, and many buyers prefer a current third-party result they can rely on during negotiations.
“The home already has a mitigation system.” That’s a good sign, but it’s still worth confirming the system is doing its job. Check that the fan is running and the manometer (the U-shaped gauge on the pipe) shows suction, and ask for any test results taken after installation. A new short-term test gives you a current reading.
“Is radon a reason to walk away?” For most buyers, no. It’s a known, measurable issue with an established fix. What matters is having accurate results early enough in your inspection window to make a plan with your agent.
“Should I retest after I move in?” The EPA suggests testing again after any major renovation to the lower level, and periodic testing is a good habit for any Wisconsin homeowner.
Frequently Asked Questions
How long does a radon test take?
Short-term radon tests for real estate typically run for at least 48 hours under closed-house conditions.
What is a safe radon level?
The EPA recommends taking action at 4 pCi/L or higher. It also notes that no level is completely risk-free, and homeowners can consider reducing levels between 2 and 4 pCi/L.
Do homes without basements need radon testing?
Yes. Any home in contact with the ground can have elevated radon, including slab-on-grade homes.
Can I sell or buy a home with high radon?
Yes. Elevated radon is usually fixable with a mitigation system, and many buyers negotiate repairs or credits.
Does HomeStart install radon systems?
No. We provide third-party testing only, so our results stay objective.
Schedule Your Radon Test
Add radon testing to your home inspection and get your answers within your inspection window. HomeStart’s full-time inspectors are credentialed by the Wisconsin Department of Safety and Professional Services (DSPS), certified through InterNACHI, and publish reports the same day. Schedule online or call (608) 609-0369, 8am–8pm, 7 days a week.
