Is Winter the Best Time to Test for Radon in Nashville?
Radon

Is Winter the Best Time to Test for Radon in Nashville?

By October 21, 2026No Comments

Winter is a good time to test for radon in Nashville. Cold weather and closed-up houses tend to push radon toward its highest levels, so a winter test is good at catching a problem. But a few winter days won’t tell you your family’s year-round exposure, and you don’t need to wait for winter. If you’ve never tested, test now. For the real annual picture, follow up with a long-term test.

At DocAir, we treat radon as a building-science problem, not a rule of thumb. Here’s why levels change with the seasons and how to get a result you can act on.

Why Radon Levels Can Be Higher in Winter

Radon is a naturally occurring radioactive gas that forms when uranium in soil and rock breaks down. You can’t see or smell it. It enters homes through cracks in foundation walls and floors, construction joints, gaps around pipes and other openings to the soil. The EPA calls it the second leading cause of lung cancer in the U.S., responsible for about 21,000 deaths a year.

The chimney (stack) effect

In cold weather, indoor air is warmer than outdoor air. Warm air rises and escapes through the upper part of the house, and replacement air gets pulled in down low. If the lower level connects to the soil through a crawl space, a basement or foundation cracks, that pull can draw in soil gas, and the radon with it.

Winter also brings closed windows, less natural ventilation and longer heating run times. Together, these can let radon climb, so a winter test may reveal a problem that a mild-weather test underestimates. Nashville’s Metro Public Health Department says the threat of radon exposure increases in the winter months, when ventilation in a home is reduced.

Not every house follows the pattern

Radon levels also respond to soil conditions, wind, barometric pressure, foundation type, ventilation and how the heating and cooling system runs. As DocAir’s radon page puts it, in homes with crawl spaces, elevated radon levels frequently trace back to radon leaks, deficient air ducts and ventilation systems creating the negative indoor air pressure that draws radon in. A blower door test can show how leaky the house is. Two houses on the same street can test very differently.

Is the Highest Reading the One That Matters Most?

Not necessarily. Test the same house during a cold snap with the heat running, then again during a mild spring week with the windows open more often, and the winter number may be much higher. Neither reading alone tells you what the family breathes over a full year.

Radon changes hour to hour, day to day and season to season. That’s why the EPA says a short-term test is less likely than a long-term test to show your home’s year-round average.

Risk depends on both how much radon you breathe and for how long. A few hours in a room with a high reading isn’t the same as living with that level for years, and a moderately elevated level that persists year after year deserves attention even if it never spikes. Concentration multiplied by time helps illustrate cumulative exposure, though it isn’t a full calculation of anyone’s dose or cancer risk. The lesson: don’t confuse a peak measurement with long-term exposure.

So When Should You Test Your Nashville Home?

It depends on what you need to know.

To find out quickly if you have a problem: test now

Radon can reach concerning levels in any season, and a properly run short-term test gives useful information. That matters most if you’re buying or selling a home, finishing a basement, turning a lower level into a bedroom or tracking down an air quality problem.

What the EPA says about short-term tests:

  • They run 2 to 90 days, depending on the device, and every radon test should run at least 48 hours.
  • Keep windows and outside doors closed as much as possible during the test, in any season (“closed-house conditions”). For a 2- or 3-day test, close them at least 12 hours beforehand, and don’t test during severe storms or high winds.
  • Normal heating and air conditioning can run, but not fans that bring in outside air.
  • Test in the lowest lived-in level, at least 20 inches off the floor, in a regularly used room (not a kitchen or bathroom), away from drafts and exterior walls.

If your first result is 4 pCi/L or higher, the EPA recommends a follow-up test. If it’s more than twice that, take a second short-term test right away rather than waiting months for a long-term result.

To understand year-round exposure: test longer

The EPA defines a long-term test as more than 90 days and says it’s more likely to reflect your year-round average. The longer it runs, the more weather and seasonal changes it captures. A test spanning all four seasons gives the best picture, and it’s a much sounder basis for a decision than a few winter days.

What Does the EPA’s 4 pCi/L Action Level Mean?

Radon is measured in picocuries per liter of air (pCi/L). The EPA recommends fixing your home when a long-term test, or the average of two short-term tests, is 4 pCi/L or higher, and considering a fix between 2 and 4 pCi/L.

That action level isn’t a line between safe and unsafe. The EPA says no level of radon is safe. The good news: according to the EPA, radon in most homes can be brought down to 2 pCi/L or below. If your first test comes back high, don’t panic, but don’t ignore it. Follow up, then decide.

Why This Matters in Nashville and Middle Tennessee

Metro Public Health notes that the EPA lists Davidson County as having high potential for elevated radon, and reports that about 40% of the 4,152 Davidson County homes tested showed elevated levels. The EPA estimates that nearly 1 in 15 U.S. homes has elevated radon, and says any home may have a problem, new or old, well-sealed or drafty.

That doesn’t mean every home in Nashville or in Williamson County towns like Franklin and Brentwood has a radon problem, and a county’s risk rating can’t tell you what’s happening in your house. The only way to know is to test.

The DocAir Approach: Measure What Matters

The right testing plan depends on the question you’re asking:

  • Want a quick screening? Run a short-term test under closed-house conditions.
  • Got an elevated result? Follow up before deciding on mitigation.
  • Want your year-round level? Use a long-term test of more than 90 days, ideally across several seasons.
  • Got a result that doesn’t add up? Look at the building’s pressure, ventilation, foundation and HVAC operation, not just the calendar.

The goal isn’t the highest number or the lowest. It’s reliable information you can base a decision on.

Ready to test your home? DocAir provides radon testing for homes in Nashville. If levels come back high, we find out why before we recommend a fix. Call (615) 373-2498 or see our radon testing and mitigation in Nashville.

Frequently Asked Questions

Are radon levels higher in winter?

Often, yes. The chimney effect, closed windows and longer heating run times can pull more soil gas into a home. But not every house follows that pattern, and levels change day to day in any season.

How long should a radon test take?

At least 48 hours, according to the EPA. Short-term tests run 2 to 90 days. Long-term tests run more than 90 days and better reflect your year-round average.

Do I have to keep my windows closed during a radon test?

Yes. For a short-term test, keep windows and outside doors closed as much as possible, except for normal coming and going. For a 2- or 3-day test, close them at least 12 hours before you start.

My summer radon test was fine. Should I test again in winter?

It can be worth it, since levels vary by season and a short summer test may not reflect winter conditions. A long-term test that spans more than one season will tell you more than two snapshots.

What should I do if my radon level is between 2 and 4 pCi/L?

The EPA recommends considering a fix in that range, because levels below 4 pCi/L still carry some risk. A long-term test can confirm where your home really sits.

Can I test for radon myself?

Yes. The EPA notes that low-cost do-it-yourself test kits are available by mail and in some hardware stores. Follow the kit’s instructions and mail it back to the lab right away. For a real estate deal, or results that are high or confusing, a professional test and evaluation can help.

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