Is Radon Higher in Winter in Utah?
It can be. In winter, Utah homes stay closed, the furnace runs and warm air rising inside the house can draw more soil gas in through the foundation. In one Utah home we tested, radon read 1.4 pCi/L in April and 7.2 pCi/L in winter, above the EPA action level of 4.0.
Utah Radon Defense · Updated October 2026
A Summer Test Is Not a Winter Number
We tested the same Utah home twice. In April, with the windows open, it read 1.4 pCi/L , a number most families would feel good about. When we tested it again in winter, closed up with the furnace on, it read 7.2 pCi/L .
Same house, a different season. That is why a single test from spring or summer can give a family a sense of safety that does not hold up in January.
If your last test was in summer, or years ago, winter is the right time to find your winter number.
Why Radon Can Rise in Utah Winters
Radon is a radioactive gas that forms naturally in the soil under Utah homes and moves up through cracks in the foundation, gaps around pipes, sump pits and crawlspaces. Three things about winter make it easier for that gas to build up inside.
The house stays closed
In summer, open windows and doors let indoor air mix with outdoor air. In winter, Utah homes stay sealed for months, so radon that gets in has fewer ways out.
Warm air rises
When the furnace runs, warm air rises and leaks out near the top of the house. That lowers the pressure near the foundation, and the house pulls more soil gas in from below. This is often called the stack effect.
Families spend more time inside
Winter does not only change the level. It changes how many hours your family breathes that air, especially in basements turned into bedrooms, offices and play areas.
When Is the Best Time to Test for Radon in Utah?
Short 2 to 3 day tests were designed for home sale deadlines. The most reliable picture comes from a short test done in winter, or a long-term test of 90 days or more. If you only test once, test while the house is closed up and the heat is on.
Across Utah, about 1 in 3 homes tested come back high. In South Jordan, 14 of the 45 homes we tested in the past year without a system were above 4.0.
DIY kit
- Designed for home sale deadlines
- You place it and mail it in yourself
- One number, from one moment in one season
Professional winter test
- A certified Radon Measurement Professional decides where to place the devices, and how many
- A continuous monitor measures radon at least hourly for 48 to 96 hours
- A detailed PDF report with all radon activity, plus temperature, pressure and humidity
- A consultation to explain your levels and your options
Already used a kit? A kit is a starting point. If it came back high, or you tested in summer, a professional number is the next step. See what radon testing costs.
What Your Winter Radon Number Means
Use the EPA action level of 4.0 pCi/L as your line. In our field experience, homes without a system rarely read below 2, most read between 2 and 15, and the highest we have measured was 490 pCi/L.
Fix your home. We come out, look at your foundation and design your system before we quote. See radon mitigation cost in Utah.
Our advice is to consider fixing it, or at least test again in winter to see how high it goes.
A good number, as long as it was measured in the right season.
Already have a radon system? Winter is a good time to check it. Look at the manometer on the pipe, and if your fan sounds different or has gone quiet, read what to check when a radon fan is noisy or not working.
Radon in Winter: Common Questions
Is radon higher in winter?
It can be. In winter, homes stay closed, the furnace runs and warm air rising inside the house can draw more soil gas in through the foundation. In one Utah home we tested, radon was 1.4 pCi/L in April and 7.2 pCi/L in winter. Not every home changes that much, which is why each home needs its own test.
When is the best time to test for radon in Utah?
The heating season. Short 2 to 3 day tests were designed for home sale deadlines, so the most reliable picture comes from a short test done in winter, or a long-term test of 90 days or more.
I tested in summer and it was low. Should I test again?
Yes, if you have not tested in winter. A summer result is one number from one season. If your summer number was between 2 and 4, a winter test is especially important, because that is where a seasonal rise can push a home over the EPA action level of 4.0.
Do I need to keep windows closed during a radon test?
Yes. Short-term radon tests are run under closed-house conditions: windows and outside doors stay closed, except for normal coming and going, during the test and for 12 hours before it starts. In a Utah winter that usually happens on its own.
What radon level should I act on?
The EPA recommends fixing a home at 4.0 pCi/L or above. Between 2 and 4, our advice is to consider fixing it, or at least test again in winter to see how high it goes.
Find Your Home's Winter Radon Number
Radon has no smell, no taste and no warning signs. A professional winter test gives you a clear answer, and if it comes back high, we design the right system for your home before we quote.
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