Why is radon more prominent in homes?

Radon builds up in homes because a house pulls soil gas in through the foundation, then traps it. Radon is a natural gas that forms as uranium breaks down in soil and rock. Outside it mixes with open air and stays low. Indoors it has nowhere to go, so it accumulates. The EPA action level is 4.0 pCi/L, and you should consider fixing between 2 and 4 (EPA).

Here is what happens under your feet. Warm air rises and leaks out the top of your house. That pulls replacement air in from the lowest point. The basement. Building science calls this the stack effect, and it works like a chimney. Your foundation sits on soil that is always making a little radon. The house pulls that gas up through cracks, the floor wall joint, sump openings, and gaps around pipes.

Older New England homes feel this more. Dirt and fieldstone foundations have a lot of open surface for gas to seep through. Even a poured slab has small cracks. Radon does not need a big hole. It rides in on the air the house is already pulling.

Winter makes it worse here. We seal up tight, the heat runs, and the stack effect gets stronger. So the most radon often shows up in the coldest months, which is also when families spend the most time in finished basements.

A few things drive how much radon a home holds:

• How much uranium is in the local bedrock. Parts of NH, ME, and MA sit on granite, which tends to make more radon (NH DHHS).
• How the house breathes. Tighter homes and a stronger stack effect pull more gas.
• The foundation type. Dirt, fieldstone, and cracked slabs give gas more ways in.
• Where you spend time. A finished basement bedroom matters more than an unused crawl.

You will not see it or smell it. The only way to know your number is a test. A short-term radon test is cheap and the fee runs $50, credited toward the job if you move ahead. If your level comes back at or above 4.0, fixing it is the move.

If you do need a fix, the answer is a mitigation system, not caulk. The crew installs an active sub-slab system. A pipe and a quiet fan pull the radon from under the slab and vent it up above the roofline before it can enter the house. For a dirt or fieldstone crawl, we use sub-membrane depressurization, where a sealed membrane goes down first and the fan pulls from under it. We do install these. Radon mitigation runs $900 to $6,000, and most homes land around $1,950 to $2,250, and the system carries a 10-year warranty.

One plain point. Sealing every crack will not fix a high radon number on its own. You need the fan moving air, or the gas just finds another path. So you do not need to chase cracks first. You need a real system.

Radon and water often travel the same paths into a basement. If you already see moisture or a damp finished space, it is worth handling both at once. Our radon lead, Branden (we call him B-Radon), can look at the whole picture.

We serve New Hampshire, Maine, and Massachusetts, and the inspection is free.

Learn more about radon mitigation, basement waterproofing, and our crawl space services. Every install is backed by the 603 guarantee.

For the science and current guidance, see the EPA’s radon pages, NH DHHS radon program [verify], and DOE Building America.

Want your number? Call us at 603-610-1770 or book your free inspection. We will get you a quote within 24 hours!

Related questions

What radon level is safe? There is no truly safe level, but the EPA sets the action level at 4.0 pCi/L and says to consider fixing between 2 and 4 (EPA). The only way to know yours is a test.

Does a radon system fix a high number for sure? A proper active system pulls radon from under the slab and vents it out. We back it with a 10-year warranty. We do not guarantee a specific radon level unless it is put in writing.

Do I need to retest after a system goes in? A retest is the homeowner’s call and is not part of the install. Testing again confirms the new number for your records.

Is radon worse in a basement than upstairs? Usually yes. The basement is closest to the soil and is where the house pulls air in, so levels are highest there and drop on upper floors.