Yes, new homes should be tested for radon, even ones built with radon-resistant features. Radon comes from the soil, not from age or construction quality, so a brand-new home in Merrimack or Nashua can test just as high as a house built in 1960. If you’re closing on new construction, the only way to know your air is safe is to test it after you move in, not just assume the builder’s features handled it for you.
Do Builders Automatically Test New Homes for Radon?
No. Builders in high-radon areas may install radon-resistant new construction (RRNC) features, like a gravel layer, a vent pipe, and sealed foundation gaps, but installing those features is not the same as testing. The EPA is clear that every new home should still be tested for radon after occupancy, even when RRNC techniques were used.
Think of RRNC like a home’s rough plumbing: it’s built to code, but nobody assumes the pipes don’t leak just because they were installed correctly. A test is how you confirm the system is actually working under real conditions, not just built to spec.
Why New Construction Can Still Have High Radon Levels
Energy-efficient, airtight building envelopes
Modern homes are sealed tighter than older construction to save on heating and cooling. That’s good for your energy bill, but it also means less natural air exchange, so any radon that does get in has fewer ways to escape. A drafty 1920s farmhouse can actually vent radon out faster than a brand-new, well-insulated build.
Soil disturbance during construction
Radon is produced by decaying uranium in soil and rock, and it’s already present under the lot before a single wall goes up. Excavation and grading can disturb that soil, and in New Hampshire’s granite-heavy bedrock, radon potential is a known regional factor regardless of when the home was built. Fill dirt brought in from elsewhere can carry its own radon-producing minerals too.
Our lead inspector, Steve Mangekian, a New Hampshire Licensed Home Inspector and InterNACHI member, has run radon tests across new builds and century-old homes throughout NH, MA, and ME. The pattern holds everywhere: the home’s age tells you nothing about its radon level. Only a test does.
How Radon Testing Works in a Newly Built Home
- Placement: A radon monitor goes at the lowest livable level of the home, usually the basement or lowest floor.
- Closed-house conditions: Windows and doors stay closed for the testing period so outside air doesn’t skew the reading.
- Duration: Short-term tests run 48 hours to a week; long-term tests run 90 days or more for a more accurate annual average.
- Results: The EPA’s action level is 4 pCi/L. Below that, you’re in the clear. At or above it, mitigation (usually a sub-slab depressurization system with a fan) is the next step.
If you’re scheduling this alongside a new construction walkthrough, Alpha’s radon testing services use an Electronic Radon Monitor that collects continuous readings, which is more reliable than a passive charcoal kit picked up at a hardware store. Pairing it with a full new construction inspection before you close means nothing gets missed before the sheetrock goes up.
Related Questions to Explore
Do new homes need radon testing if they have radon-resistant features? Yes. RRNC features reduce the odds of a problem, but only a test confirms the actual level in your specific home.
Why do energy-efficient new homes sometimes have higher radon levels? Tighter building envelopes trap indoor air, including any radon that seeps in, instead of letting it naturally exchange with outdoor air.
Is radon testing required by law for new construction in New Hampshire? New Hampshire doesn’t mandate radon testing statewide, but the EPA and most real estate transactions strongly recommend it, and some towns require RRNC features in high-potential zones.
How long does a radon test take in a new home? A short-term test takes 48 hours to a week. If you want a full annual picture, a long-term test runs 90 days or more. If you’re deciding between a continuous monitor and a basic kit, this guide to choosing a radon monitor breaks down the tradeoffs.
What radon level is considered unsafe? The EPA sets 4 pCi/L as the action level. Levels between 2 and 4 pCi/L still carry risk and are worth addressing if it’s easy to do. One thing that won’t help: an air purifier. Air purifiers don’t remove radon gas, since radon needs mitigation at the source, not air filtration.
When to Call a Professional
If your new home tests at or above 4 pCi/L, or even in the 2 to 4 range and you’d rather not take the risk, it’s time to call a licensed radon professional rather than DIY it. Installing or upgrading a sub-slab depressurization system involves sealing, venting, and sometimes electrical work for the fan, and getting it wrong can trap radon instead of removing it. The EPA’s guidance on addressing radon in new construction recommends a qualified contractor for exactly this reason.
Alpha Building Inspections serves Merrimack and the wider NH, MA, and Maine seacoast area, and can test a new build before you close or right after you move in.
Conclusion
New construction doesn’t get a pass on radon. Builders can reduce the risk with RRNC features, but soil, bedrock, and airtight construction mean the only way to know your home’s actual radon level is to test it. Key takeaways:
- Radon-resistant features are a head start, not a substitute for testing
- New, energy-efficient homes can trap radon just as easily as old ones
- 4 pCi/L is the line where mitigation becomes worth it
Ready to test your new home? Schedule radon testing with Alpha Building Inspections or get in touch with our team with any questions
