What is a mitigation system for radon?

A radon mitigation system is a fan and pipe setup that pulls radon gas out from under your house and vents it above the roofline before it gets into the air you breathe. The most common type is active sub-slab depressurization. A pipe goes through the basement floor into the gravel under the slab, an inline fan runs on it 24/7, and the suction draws the gas up the pipe and out. For a dirt or fieldstone crawl space, we use sub-membrane depressurization instead, which pulls the gas from under a sealed floor barrier. At 603 we install both. A typical install runs $900 to $6,000, and most homes land around $1,950 to $2,250.

What radon is and why the system works

Radon is a colorless, odorless gas that seeps up out of the ground. New Hampshire and Maine sit on a lot of granite, and granite is a big radon source, so we see high readings here all the time. The gas moves up through cracks in the slab, the floor wall joint, and gaps around pipes. Your house pulls a slight vacuum on the soil below it, so it draws the gas right in.

A mitigation system flips that. The fan keeps the area under the slab at lower pressure than the basement, so the gas takes the easy path up the pipe instead of into your living space. Run nonstop, it keeps the level down.

The EPA sets the action level at 4.0 pCi/L, and says to consider fixing between 2 and 4 (EPA, epa.gov/radon). If your test came back at 4.0 or higher, you want a system. NH DHHS publishes the same guidance for homes in our area.

What a real install looks like

For a poured slab, we core a hole in the floor, run a sealed pipe down into the gravel, and mount an inline fan on the pipe run. The pipe carries the gas up and out above the roof. We seal the slab penetrations and the floor wall joint along the way, because a tight slab makes the fan work better.

For a dirt-floor or fieldstone crawl, there is no slab to draw through. We lay a sealed membrane over the dirt, seal the seams, and pull the suction from under that. Same idea, different surface.

Branden runs our radon side. The crew calls him B-Radon, and he holds the state radon cert (RMS-113966). 603 is OSHA-certified, licensed and insured. NH does not issue a GC license number, so nobody in this state has one to show you.

What drives the cost

The price moves with your foundation. A single poured slab with an easy fan and pipe path is the lower end. A house that needs two suction points, a long pipe run to get above the roofline, or a crawl space membrane runs more. A finished basement can add labor because we route the pipe around the finish. We give you a real number after we look, and the quote comes within 24 hours.

If you only need a test first, that runs $50, credited toward the job if you move ahead.

Here is the part most contractors skip. You do not always need the biggest system. If your reading sits in the 2 to 4 range, the EPA says consider it, not must. We will tell you where your number actually lands and what it would take. No upsell.

One thing we are clear about up front. Our radon mitigation warranty is 10 years on the system. We do not guarantee a specific radon level unless we put that in writing for your house. After install, the retest is your job, and it should be done. We will explain how.

NH framing

Granite country means radon country. A lot of homes in New Hampshire, Maine, and Massachusetts test high, and a fieldstone foundation in an older New England house can pull gas straight up through a dirt floor. If you are already fixing water down there, it is a good time to handle radon too, since the crew is in the basement either way.

Want to know your number? Book your free inspection and we will get you a test and a quote. Call us at 603-610-1770. Every system we put in is backed by the 603 guarantee!

Related questions

Do I need radon mitigation if my test came back at 3.5 pCi/L? You are in the range where the EPA says consider it (epa.gov/radon). It is not a must at 3.5, but plenty of homeowners fix it for peace of mind, and we can walk you through the call.

Does radon mitigation work in a crawl space with a dirt floor? Yes. We use sub-membrane depressurization. We seal a barrier over the dirt and pull the gas from under it. See our crawl space services.

Is radon connected to my wet basement problem? They are separate problems with one shared path. Both move through cracks and the floor wall joint. If we are already sealing those for water on the basement waterproofing side, radon work fits right in.

What is the warranty on a radon system? 10 years on the radon mitigation system. We do not guarantee a radon level unless it is in writing for your home.