A Michigan home energy audit checks insulation, air sealing, and HVAC efficiency — but auditors don't always test for radon, even though the same depressurization and air-sealing changes they recommend can raise indoor radon levels. Here's how to fold a proper radon test into your 2026 energy audit so you're not tightening up your house and trapping soil gas inside it.
- Test for radon before and after energy audit air-sealing work — sealing a house tighter can raise radon levels 20-30% in some Michigan homes.
- A 48-hour short-term kit placed in the lowest lived-in level gives audit-ready results fast.
- Closed-house conditions for 12 hours before and during the test are non-negotiable for accurate numbers.
- Above 4 pCi/L, schedule mitigation before finishing any air-sealing upgrades from the audit.
Why this matters
Energy audits in Michigan homes usually end with a punch list: seal the rim joist, air-seal the attic hatch, add a door sweep to the basement stairs. Every one of those fixes reduces how much outside air leaks into the house — which also reduces how much soil gas gets diluted before it reaches the living space.
A house that tests at 3.8 pCi/L before air sealing can climb past the 4 pCi/L EPA action level after the work is done. That's not a hypothetical for Michigan — glacial till soils across Metro Detroit and the Lansing area sit on uranium-bearing bedrock, and tighter homes hold radon in rather than venting it out. Testing before and after the audit tells you whether the upgrades pushed your numbers in the wrong direction.
What you'll need
- A short-term radon test kit (charcoal canister or alpha track, EPA-approved)
- A spot on the lowest lived-in level, away from drafts, exterior walls, and HVAC vents
- 48 continuous hours of closed-house conditions
- Your energy auditor's blower-door test schedule, so testing doesn't overlap with it
- A pen and the test kit's start/stop log sheet
- A follow-up plan if results come back at or above 4 pCi/L
If you'd rather skip the guesswork on which kit to buy, the current lineup of best radon test kits for Michigan homeowners covers both charcoal and alpha-track options rated for Michigan's climate.
The steps
1. Test before the audit starts
Run your radon test first, before the auditor touches insulation or does a blower-door test. This gives you a baseline number that reflects how your house behaves under normal, everyday conditions in 2026 — not conditions altered by testing equipment.
Skipping this step is the most common mistake homeowners make. Without a baseline, you have no way to tell whether elevated post-audit radon came from the audit's air sealing or was already there.
2. Pick the right room
Place the kit in the lowest level of the home that's regularly occupied — a finished basement rec room, not a crawl space or unfinished mechanical room. Keep it at least 20 inches off the floor, away from windows, exterior doors, and any fan or vent.
The location matters because radon concentrations vary by floor level; testing in an unused mudroom or utility closet under-reports what you're actually breathing in the living space. Prepare your basement for a radon test walks through exact placement rules room by room.
3. Close the house 12 hours before starting
Shut all windows and exterior doors 12 hours before you start the test, and keep them closed for its full duration. Normal entry and exit through one door is fine — propping doors open or running window fans is not.
This step exists because open windows dilute soil gas with outside air, giving you an artificially low reading. A test done with windows cracked open in July tells you almost nothing useful.
4. Coordinate around HVAC and audit equipment
Don't run whole-house fans, and don't let your energy auditor perform a blower-door depressurization test while your radon kit is running. A blower door pulls air through the entire building envelope and will distort the radon reading in either direction.
Schedule your radon test to finish before the auditor's blower-door test begins, or wait until after that portion of the audit is done. Overlapping the two tests is the second-most common mistake homeowners make when trying to combine radon testing with a Michigan home energy audit.
5. Run the test for a full 48 hours
Short-term kits need a minimum of 48 continuous hours to produce a reliable reading — pulling the kit early to "check" it invalidates the sample. Log your exact start and stop times on the kit's included sheet; labs use those timestamps to calculate concentration.
Winter months give the most representative results for radon testing in Michigan homes, since houses are sealed tightest during heating season. Time a radon test for accurate winter results if your audit is scheduled for the colder months, which is when most Michigan energy audits happen anyway.
6. Mail the kit and wait for lab results
Seal the kit immediately at the 48-hour mark and mail it the same day, following the return instructions printed on the packaging. Most Michigan-based labs return results in 3-5 business days once they receive the sample.
A delayed mail-in — sitting on a counter for a week — skews the lab's reading, since charcoal canisters keep absorbing radon and off-gassing after the test window closes.
7. Retest after audit air-sealing work is finished
Once the auditor completes insulation and air-sealing upgrades, run a second 48-hour test using the same location and protocol. Compare the two numbers directly.
If the post-audit result climbed toward or past 4 pCi/L, that's your signal to act before you consider the energy upgrade complete — a tighter house with elevated radon isn't actually a healthier house.
Get radon testing scheduled
NRPP-certified testing and mitigation for Metro Detroit and Lansing homeowners.
Troubleshooting
Result came back higher after the audit. This is the exact scenario the before/after test is designed to catch — air sealing reduced natural ventilation and radon concentrated. Schedule mitigation before calling the energy upgrade finished.
Kit was disturbed mid-test. Pets, kids, or a contractor moving the canister invalidates the sample. Restart the full 48 hours rather than guessing at how much the reading was affected.
Windows were open during a heat wave. Reschedule for a period when you can keep the house closed. A summer test with windows open for ventilation isn't comparable to a winter baseline.
Blower-door test ran during the radon test window. The mechanical pressure change invalidates both readings for comparison purposes. Separate the two tests by at least a day.
Reading is borderline, right around 3.5-4.5 pCi/L. Run a second short-term test or step up to a 90-day long-term test for a clearer picture before deciding on mitigation. One-time readings near the action level can vary with weather and barometric pressure.
You don't know what the number actually means. Read your radon test results breaks down pCi/L thresholds and what each range means for next steps.
Tools and resources
- EPA-approved short-term test kit rated for residential use
- A copy of your energy auditor's testing schedule, so radon and blower-door tests don't overlap
- How to test your home for radon for the full step-by-step protocol beyond the audit-specific timing notes above
- A lab that turns results around in under a week — most Michigan homeowners see results within 3-5 business days in 2026
- A follow-up plan for mitigation if results land at or above 4 pCi/L
“A radon test only means something if the house is sealed like it’s the middle of a Michigan winter.”
FAQ
What’s the best time to test for radon during a home energy audit in Michigan?
Test before the audit’s air-sealing work begins, then retest after it’s complete, ideally during the heating season from October through March when homes stay sealed tightest and results are most representative.
Does an energy audit make radon levels worse?
Air-sealing upgrades from an energy audit can raise indoor radon levels because they reduce natural ventilation that previously diluted soil gas. This is why testing before and after the audit matters more than a single one-time reading.
Is radon testing required as part of a Michigan home energy audit in 2026?
No, most standard Michigan home energy audit programs don’t mandate radon testing, but pairing the two catches ventilation changes that could push radon above the EPA’s 4 pCi/L action level.
How much does a short-term radon test kit cost in Michigan?
Short-term charcoal or alpha-track kits typically run in the range most hardware stores and online retailers post, with lab analysis often included in the kit price. Check current pricing before buying, since it varies by kit type.
Can I run a blower-door test and a radon test at the same time?
No. A blower-door test depressurizes the entire house and will distort radon readings in either direction, so schedule the two tests on separate days or in sequence.
What radon level requires mitigation in Michigan?
The EPA action level is 4 pCi/L. At or above that number, mitigation is recommended, and Michigan’s glacial till soils mean many homes in the Metro Detroit and Lansing areas test above that threshold even before any air-sealing work.
How long does a short-term radon test take?
A short-term test requires a minimum of 48 continuous hours with the house closed up, followed by 3-5 business days for most Michigan labs to return results.
Should I test for radon in the basement or the main floor?
Test on the lowest lived-in level of the home, which is usually the basement if it’s finished and occupied. Testing in an unfinished crawl space or mechanical room under-reports what occupants actually breathe.
One last thing
Most homeowners assume a radon test is a one-and-done box to check before selling a house. It's not — any project that changes how your house breathes, including a 2026 energy audit, is a reason to test again. The 48 hours it takes is short compared to the alternative of finding out years later that a well-intentioned insulation upgrade sealed radon in along with the heat.
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