Why Homes Have a High Level of Radon Concentration

The best way to test for Level of Radon Concentration in your house is with a short-term or long-term test kit placed in the lowest lived-in level of your home, since that is where the gas concentrates first. Wisconsin’s geology makes this especially relevant here: roughly 1 in 10 Wisconsin homes has radon at or above the EPA’s action level, and the gas can show up in the air of a finished basement, a slab-on-grade first floor, or a private well.

Key Factors Driving High Wisconsin Level of Radon Concentration:

Level of Radon Concentration in homes can vary depending on several environmental and structural factors. These include the soil composition beneath the house, the way the home is built, and even the ventilation of the space. Let’s take a closer look at the primary reasons why radon can accumulate at high levels in homes:

• Geological Composition: Wisconsin’s bedrock and soil, particularly in areas with high sand and gravel content, allow radon to move easily up from the ground. The region’s geological history, including glaciers, left behind materials that naturally emit high amounts of radon as uranium breaks down.
  
• Soil Permeability: Looser, porous soils allow radon gas to escape from deep in the earth and move easily into the air pockets around building foundations.
  
• The “Stack Effect” and Weather: During Wisconsin’s cold winters, homes are sealed tight to conserve heat. Heated air rises and escapes, creating a vacuum in the basement that draws more soil gas and thus radon inside.
  
• Entry Points: Radon seeps through small cracks, construction joints, and gaps in foundations or basements.
  
• Regional Specifics: While common state-wide, radon risk is significantly higher in certain regions, such as northwest Wisconsin and Jackson County, where over one-third of homes have tested above the action level.

Radon is a naturally occurring gas that can accumulate in homes, leading to potentially harmful concentrations. High levels of radon in homes can happen due to factors such as the geological composition of the area, the construction of the building, and even weather patterns.

If you live in areas like Whitefish Bay, West Allis, Wauwatosa, or Shorewood, radon may be more prevalent than you think. It’s crucial to understand why Level of Radon Concentration in your home can be high, and how you can protect your health with radon testing services and professional radon mitigation.

Why Wisconsin Homes Get High Radon Levels

Radon forms when uranium in soil and bedrock breaks down. Wisconsin sits on a mix of glacial sand, gravel, and dolomite bedrock that lets the gas move upward easily, and Milwaukee-area neighbourhoods like Whitefish Bay, West Allis, Wauwatosa, and Shorewood share that same underlying geology. A few structural and seasonal factors compound the issue:

• Soil permeability — loose, porous soil lets Level of Radon Concentration gas migrate freely toward the surface and into any air pockets around a foundation.
• The stack effect — during Wisconsin winters, heated air rises and escapes through the upper floors, creating a slight vacuum in the basement that pulls in more soil gas.
• Entry points — radon seeps through foundation cracks, sump pits, construction joints, and gaps around pipes.
• Tighter, more energy-efficient construction well-sealed homes hold radon indoors instead of letting it dissipate.

How to Test for Radon in Your House

Testing is the only reliable way to know your home’s Level of Radon Concentration; there is no way to see, smell, or otherwise sense it. Two testing approaches cover most situations:

• Short-term test (2–7 days): Fast results using a charcoal canister or electronic monitor. Good for a first check or a real-estate transaction deadline.
• Long-term test (90+ days): Captures seasonal swings in radon, since levels typically run higher in winter with windows closed. This gives the most accurate year-round picture.

Place the detector in the lowest level of the home people regularly spend time in, away from drafts, exterior walls, and direct sunlight, and keep windows closed for the duration of a short-term test. DIY kits are affordable and EPA-recognized, but a certified tester adds proper placement, chain-of-custody documentation for real-estate transactions, and interpretation of the result against Wisconsin’s testing guidance.

Are There Signs Radon Is in Your Home?

No. Radon has no smell, colour, or taste, and it does not trigger allergy-like symptoms the way mold or dust can. Any physical effects, most notably an elevated long-term lung cancer risk, develop silently over years of exposure rather than showing up as an acute symptom. That is exactly why testing, not observation, is the only dependable method a home can look and feel completely normal while still testing well above the action level.

Radon in the Basement vs. the Rest of the Home

Radon enters through whatever part of the structure sits closest to the soil, so basements and slab-on-grade floors see it first and typically test highest. But Level of Radon Concentration does not stay put: normal air circulation and the stack effect carry it upstairs, so a home without a basement or with a crawl space is not automatically safe. Homes built on a slab, over a crawl space, or with a walk-out basement can all register elevated readings the right response in every case is the same test, placed at the lowest occupied level.

Can Radon Get Into Well Water?

Yes. Radon dissolves into groundwater the same way it moves through soil gas, and private wells drawing from Wisconsin’s granite or dolomite aquifers can carry measurable radon. There is currently no federal EPA drinking-water standard for radon (a limit was proposed in the 1990s but never finalized), so results are typically compared against state laboratory guidance rather than a hard legal limit. Level of Radon Concentration in water becomes airborne every time water runs showering, washing dishes, running a dishwasher which adds to a home’s indoor air level on top of whatever soil gas is already entering through the foundation.

If your home relies on a private well, water testing is a separate process from air testing and worth doing alongside it our Radon Water Testing guide walks through how to sample and interpret a well-water result.

How Common Is Radon in Wisconsin Homes?

The U.S. average indoor radon level is about 1.3 pCi/L, and the EPA recommends fixing any home at or above 4 pCi/L, with 2–4 pCi/L worth considering as well. Radon is the leading cause of lung cancer among non-smokers and the second-leading cause overall, contributing to an estimated 21,000 lung cancer deaths nationwide each year. In Wisconsin specifically, state health data puts elevated radon in roughly 1 in 10 homes tested a rate high enough that the Wisconsin Department of Health Services recommends every home be tested, regardless of neighbourhood or home age.

What to Do If Your Test Comes Back High

A result at or above 4 pCi/L calls for radon mitigation, most commonly an active soil depressurization system that vents soil gas from beneath the foundation to the outside before it can enter the living space. Sealing major foundation cracks and improving basement ventilation can help at the margins, but they are not substitutes for a properly designed mitigation system on a confirmed high result.

FAQs

Conclusion

Radon is invisible, but a test result is not — and once you have one, the next step is straightforward. For the full walkthrough of what a professional radon test involves and how results are interpreted, see our

Radon Testing pillar guide. If a result comes back elevated, our Radon Mitigation Systems guide explains how an active soil depressurization system brings levels down. For background on what radon is and why it matters, start with our Understanding Radon pillar guide.

Ready to find out where your home stands? Schedule professional radon testing and mitigation with our certified team, or call 414-455-7279.