Radon Mitigation: What to Know Before You Hire

What is Radon Mitigation and how does it work?

Radon mitigation is a system that pulls radon gas from the soil beneath your home and vents it safely above the roofline. The most common setup, active soil depressurization, uses a fan to create suction under the slab, so the gas never enters your living space.

Radon is a radioactive gas that comes from the natural decay of uranium in the ground. It seeps up through the soil and can get pulled into your home through cracks in the foundation, gaps around pipes, or sump pits. Once inside, it can build up to levels that are dangerous to breathe. The EPA and the U.S. Surgeon General recommend fixing any home that tests at or above 4.0 pCi/L. (alabamapublichealth.gov)

The standard fix is called active soil depressurization, or ASD. A contractor drills a hole through your slab floor, digs out a small pit underneath, and inserts a pipe that runs from that pit up through the house to the roofline. A fan installed in that pipe (often in the attic or outside) creates a vacuum under the slab, drawing the radon-laden air out and venting it safely above your roof. The system also seals the hole around the pipe and any other major entry points, so the suction is effective.

For homes with a crawl space, the approach differs. Instead of a slab penetration, the crew lays a heavy plastic membrane over the dirt floor, seals it to the foundation walls, and runs a suction pipe under the membrane. That's called a sub-membrane system, and it's more involved, which is why it costs more. On a slab home, the process is usually straightforward and can be done in a day.

• Active soil depressurization is the most common method for slab and basement homes.
• Crawl space homes use a sealed sub-membrane system.
• Lowering indoor radon levels to below 4.0 pCi/L is the goal, ideally to 2.0 or lower.

How Radon Mitigation Works, Start to Finish

The process starts with a thorough inspection of your home's foundation, then a hole is cut in the slab, a suction pit is dug, and a pipe with a fan is routed to the roofline. The crew seals all major entry points, and the system is tested to confirm it's pulling properly.

Before we break out the jackhammer, we walk your home to figure out the best route for the pipe. That means checking the foundation type, the location of interior walls, and where the roof line sits. We look for existing cracks, utility penetrations, and sump pits that need sealing. A home with a basement, a slab-on-grade, or a crawl space each get a different approach, and the layout of your house determines how the pipe runs.

For a slab home, the crew cuts a hole in the floor, usually in a closet or utility room, and digs out a small cavity underneath. That cavity gives the fan enough space to pull air from under the entire slab. The pipe goes in, sealed tight to the floor, and runs up through the house, often inside a closet or along an exterior wall, then out through the roof. The fan gets mounted in the attic or on the exterior, and it runs continuously.

Once the system is in, we run a post-mitigation test to confirm radon levels have dropped. That test takes at least 48 hours, and we leave a manometer, a small gauge on the pipe, so you can check the system is working. The gauge shows a vacuum reading; if it drops, you know there's a problem. We also seal any visible cracks in the slab and around pipes, because suction can pull more gas through those gaps if they're left open.

The whole process usually takes a day, sometimes two if the house is large or the route is complicated. The crew handles the permit, which is required in Huntsville and typically runs $25 to $150. (angi.com) You don't need to be home for the installation, but you'll want to be there for the final walkthrough so we can show you how the system works and answer questions.

1. Inspect the foundation.We check the slab, crawl space, or basement to find the best suction point and route for the pipe.
2. Cut the hole and dig the pit.A 4 to 6 inch hole is cut in the slab, and a small cavity is dug underneath to maximize suction.
3. Install the pipe and fan.The pipe runs from the pit to above the roofline, with a fan installed to pull the gas out.
4. Seal entry points.Cracks, gaps, and sump pits are sealed so radon can't sneak in through other paths.
5. Test and wrap up.A post-mitigation test confirms levels are down, and we show you the manometer and answer questions.

Why Radon Mitigation Matters for Your Home

Radon is the second leading cause of lung cancer in the U.S., and it's a problem in Madison County. The only way to know your exposure is to test, and if levels are high, mitigation is the most effective way to protect your household.

Madison County is one of the 15 Alabama counties the state names as having the highest radon potential, alongside Colbert, Franklin, Jackson, Lauderdale, Lawrence, Limestone and Morgan across north Alabama. (alabamapublichealth.gov) That doesn't mean every home in Huntsville has a problem, but it does mean the geology here is prone to it. The only way to know for sure is to test.

Radon has no smell, no color, and no immediate symptoms. You could live with high levels for years and never notice until health problems show up. That's why the EPA and the Surgeon General recommend testing every home, and fixing any that come in at or above 4.0 pCi/L. (alabamapublichealth.gov) A simple test kit from a hardware store or a professional test can tell you where you stand.

If your home tests high, mitigation is not a luxury. It's a straightforward fix that lowers radon levels dramatically, often to well below the EPA action level. The system runs in the background, using a small amount of electricity, and it's a one-time installation. Compared to the health risk, the cost is modest, and it adds value to your home in the sense that future buyers will see a safe, tested property.

Common Problems and What Causes Them

Most radon mitigation issues come down to a few recurring problems: a system that wasn't installed right, a fan that's worn out, or a home that has a tricky layout. Here's what to watch for and what typically causes it.

One of the most common issues we see is a system that was installed but never tested afterward. The fan might be running, but if the suction pit is too small or the pipe route is too long, radon levels can stay high. A proper installation includes a post-mitigation test, and any contractor who doesn't do that is leaving you guessing.

Another frequent problem is a radon fan that quits. A fan is a wear item, and you should expect to replace it every 5 to 10 years at roughly $200 to $600, averaging about $350. (angi.com) If the manometer shows no vacuum, the fan has likely failed. Some fans are easier to replace than others; attic and crawl space placements cost more for access. (angi.com)

Crawl space homes have their own set of headaches. The membrane can get punctured by pets, pests, or stored items, which breaks the seal and lets radon back in. If the membrane wasn't sealed to the foundation properly, the system won't pull a good vacuum. We've also seen crawl space systems where the pipe runs through the living space without being properly sealed, which defeats the purpose.

Some homes are just harder to fix than others. A house with a large footprint, a walkout basement, or a sump pit that isn't sealed can require a more complex system. That's when costs climb. A standard active soil depressurization system runs about $800 to $1,500 installed nationally, with complex homes reaching $2,500 or more. (angi.com) In Huntsville, for a standard slab-on-grade home, expect $800 to $1,500 installed. (huntsvilleradonpros.com) Crawl space systems cost more because of the membrane and extra labor, with the membrane alone running $800 to $3,000, and full encapsulation from $1,500 to $15,000 depending on size and access. (bobvila.com)

Frequently Asked Questions