Radon in Southwest Wisconsin: Why I Recommend Testing Every Home

Radon is the one inspection item buyers try to skip to save a little money, and it's the one I push back on hardest. You can't see it, smell it, or guess at it from the age or condition of the house. The brand-new ranch and the 1890s farmhouse next door can test completely differently, and the only way to know is to measure. I'm Jeremy Fishnick, a licensed home inspector and Realtor in Lancaster, Wisconsin, and I recommend a radon test on every home I inspect in this part of the state. Here's why, and what to do with the result.

Short answer: Radon is a naturally occurring radioactive gas that seeps from the ground into homes. Southwest Wisconsin's geology produces a lot of it, and local health departments report that a large share of homes tested here come back above the EPA's recommended action level of 4 picocuries per liter (pCi/L). A test during your inspection period takes a few days and costs a fraction of what a mitigation system does, and a high result is fixable.

What radon is

Radon comes from the natural breakdown of uranium in soil and rock. Outdoors it disperses harmlessly. Indoors it collects, especially in basements and lower levels, and the EPA identifies it as the second leading cause of lung cancer after smoking. The risk comes from long-term exposure, which is exactly what living in a house is. That's why it's a buying question and not just a curiosity.

Why southwest Wisconsin in particular

The same bedrock that gives the Driftless Area its bluffs and springs tends to produce elevated radon. State and county health departments in our corner of Wisconsin have been encouraging residents to test for years. Lafayette County's health department, for example, reports that roughly half of the radon tests in county homes come back above the EPA action level, with a county average several times the national average. Grant and Iowa counties sit on similar geology. I don't quote those numbers to scare anyone. I quote them because they mean a high result here is ordinary, not a sign of something wrong with a particular house.

That also means a seller shouldn't take a radon finding personally. It's the ground, not the housekeeping.

How the test works during a purchase

When I'm hired to test, I place a continuous radon monitor in the lowest level of the home that could be lived in, following EPA placement guidelines: away from exterior walls, drafts, and the sump, at the right height, in a spot where it won't be disturbed. The monitor runs for a minimum of 48 hours, and I usually schedule it so I can set it before or at the inspection and pick it up a couple of days later. The home needs to be kept under closed-house conditions, meaning windows and exterior doors shut except for normal coming and going, starting half a day before the test and throughout. The seller is told this in advance.

A continuous monitor records hourly readings, which lets me see whether conditions changed mid-test, such as a window left open or the monitor being moved. That's one reason I prefer it to the mail-in charcoal kits for real estate transactions, which are fine for a homeowner's own curiosity but easier to compromise and slower to report.

Build the test time into your inspection contingency. A test that finishes the day after your deadline doesn't help you.

Reading the result

The EPA recommends fixing a home that tests at or above 4 pCi/L, and suggests considering mitigation between 2 and 4. There is no level considered perfectly safe, but 4 is the threshold most lenders, agents, and buyers work from. A result of 3.8 is not a pass with confetti and a result of 4.2 is not an emergency. Both tell you the home has meaningful radon and both are worth a conversation about mitigation.

Short-term tests also vary with weather and season. A reading taken in a wet, cold week when the house is sealed up tends to run higher than one taken in June with the windows cracked. A real estate test gives you a snapshot good enough to decide on, and I tell buyers who end up right near the line to retest after they move in.

What happens if it's high

Mitigation is routine. The standard fix is an active sub-slab depressurization system: a pipe is set into the slab or sump pit, a fan pulls air from under the foundation, and the gas is vented above the roofline before it ever enters the living space. A licensed mitigation contractor installs it in a day, and a follow-up test confirms it's working. Costs vary with the house, so get a local quote rather than trusting a national average, but the system is typically a small fraction of the home's price.

In a purchase, a high radon result is usually handled one of three ways:

1. The seller installs a system before closing, with a post-mitigation test showing it worked.
2. The seller credits the buyer the cost of a quoted system, and the buyer has it installed after closing.
3. The buyer accepts the result and handles it on their own, sometimes in exchange for other concessions.

Which one makes sense depends on the deal. What I don't recommend is ignoring it. A system that's already installed and tested is also a selling point when it's your turn to list; buyers around here know to ask. I touched on that from the seller's side in Selling Rural Property in Southwest Wisconsin: Well, Septic, and Radon.

A few things buyers get wrong

• "The house has a walkout basement, so it's fine." Not necessarily. Any part of the house in contact with the ground can let radon in.
• "The seller tested it years ago." Levels change, and so do houses. Test now.
• "There's already a mitigation system." Good. Test anyway to confirm the fan is running and the system still performs.
• "It's a slab house with no basement." Slab homes can test high too. The gas comes through cracks and joints in the slab.

If you already own your home

You don't need to be buying to test. County health departments in our area often offer low-cost or free test kits, and a do-it-yourself kit from the hardware store works for a first look. If it comes back high, confirm with a second test or a professional measurement, then call a mitigation contractor. It's one of the more fixable health risks in a house.

Talk to Jeremy

If you're buying a home in Lancaster, Platteville, Cuba City, Darlington, Dodgeville, or anywhere in the Driftless Area and want the inspection and the radon test handled together, I'm Jeremy Fishnick with The Complete Inspection and Fishnick Realty Advisors. Call or text 608-732-2564, or read about what else I look for in What's in a Jeremy Fishnick Home Inspection Report.