Can radon levels of 100 be mitigated effectively, and if so how much?

Yes. A reading near 100 pCi/L is a serious result, but it is fixable with the same active mitigation approach we use on lower numbers. A properly designed system pulls radon-laden air out from under the slab and vents it above the roofline before it ever reaches your living space. Radon mitigation typically runs $900 to $6,000, and most homes land around $1,950 to $2,250, and a radon test runs $50, credited toward the job if you move ahead. The high starting number does not change the core method. It changes how carefully the system has to be sized and sealed.

A reading of 100 is 25 times the EPA action level of 4.0 pCi/L (epa.gov/radon). That is high. It usually points to a strong soil-gas source under the house, often a dirt or fieldstone crawl, a lot of cracks, or both. None of that puts a home out of reach. Active sub-slab depressurization is the standard fix, and it scales. A bigger source just means we plan the suction points and fan around that load instead of guessing.

How the fix works at a number this high

Radon comes up from the ground. It seeps through the floor wall joint, slab cracks, and gaps around pipes. An active sub-slab system drills one or more suction points through the slab, then a fan in continuous operation draws the gas up a sealed pipe and pushes it out above the roof. We seal the obvious entry points first so the fan is not fighting open leaks. On a number near 100, we lean toward more suction coverage and we are deliberate about sealing.

If your radon is coming up through a dirt or fieldstone crawl, a poured-slab approach does not apply. There, we install sub-membrane depressurization. We lay a sealed membrane over the dirt floor and pull the soil gas out from beneath it. We install both system types, so the crawl does not change the answer. It changes the parts list.

Want the full picture on radon work? See our radon mitigation page. If a crawl is your source, the crawl space services page covers how we seal that space the rest of the way.

What drives the cost

Radon mitigation runs $900 to $6,000, and most homes land around $1,950 to $2,250. The spread on any single home comes down to a few things. How many suction points the slab needs. Whether your foundation is poured concrete, block, or a dirt crawl that needs a membrane instead. The fan size the source calls for. How far the pipe has to run to clear the roofline. A reading near 100 often lands toward the higher-effort end, since it usually wants more suction and tighter sealing than a borderline 5 or 6 would.

A radon test runs $50, credited toward the job if you move ahead. If you already tested and got 100, you do not need us to retest before we design the system. We can work from your result. One point worth saying plainly. A 10-year warranty on the mitigation work is not a guarantee of a specific post-fix radon number unless that number is put in writing. Radon comes from the ground, and ground conditions vary. We stand behind the system. We do not promise a soil reading we cannot control.

We do not retest your air after install. That part is yours to run, and we will tell you how. EPA recommends fixing at 4.0 and considering a fix between 2 and 4 (epa.gov/radon). At 100, there is no debate about whether to act.

A New Hampshire note

A lot of older New England homes sit on dirt or fieldstone foundations, and those tend to read high. NH DHHS tracks radon across the state and points homeowners toward testing and mitigation. We serve New Hampshire, Maine, and Massachusetts, and Branden, our radon lead, has run plenty of high-number jobs in exactly these soils. A 100 is not the worst we have seen, and it is squarely in fix-it range.

Curious how we back the work? Read the 603 guarantee.

Book it

Call us at 603-610-1770, or book your free inspection and we will look at your foundation, your test result, and lay out a system built for your number. Free inspection, free estimate, quote within 24 hours.

Related questions

Is a radon level of 100 dangerous? It is far above the level the EPA tells homeowners to act on. The EPA action level is 4.0 pCi/L (epa.gov/radon), so 100 is 25 times that. The fix is straightforward active mitigation, and the sooner the better.

Will mitigation get a reading of 100 all the way down to safe? A well-built active system pulls radon down hard, and high starting numbers usually drop a lot. We do not promise a specific post-fix number unless it is written into your contract, because the source is in the ground. Retesting after install is the homeowner’s step, and we will walk you through it.

Do I need a different system because my number is so high? No. It is the same active sub-slab method, or sub-membrane depressurization if you are on a dirt or fieldstone crawl. A high reading means more suction coverage and tighter sealing, not a different category of system.

How much does radon mitigation cost? Radon mitigation runs $900 to $6,000, and most homes land around $1,950 to $2,250, and a radon test runs $50, credited toward the job if you move ahead. Foundation type, number of suction points, fan size, and pipe run set where your home lands in that range. Book your free inspection for a firm quote.