What to Know Before Hiring for Radon Mitigation

What is Radon Mitigation and how does it work?

Radon mitigation is a system that pulls radioactive soil gas from under your home and vents it safely above the roofline, keeping indoor levels below the EPA action level of 4.0 pCi/L.

Radon is a colorless, odorless gas that comes from uranium breaking down in the soil. It seeps through cracks in your foundation, gaps around pipes, and sump pits. Once inside, it builds up to levels that increase lung cancer risk. Mitigation stops that.

The standard fix is active soil depressurization. A fan installed in your attic, garage, or outside creates suction under the slab. A pipe runs from that suction point through the house and out the roof. The fan runs continuously, pulling the gas out before it can enter your living space.

In Huntsville, Madison County is one of 15 Alabama counties with the highest radon potential. That's not a scare tactic, it's a fact from the Alabama Department of Public Health. Homes here are more likely to test above 4.0 pCi/L, and mitigation is the only way to fix it.

How Radon Mitigation works, start to finish

We test the air first, then install a suction point in the slab or under a crawl space membrane, run PVC pipe to a fan, and vent the gas above the roofline. The whole job takes one to two days.

Testing comes first. Professional radon testing runs $150 to $700 and takes 48 hours minimum. We place a monitor in the lowest livable level of your home, usually the basement or first floor if you're on a slab. If the result is 4.0 pCi/L or higher, we move to design.

For slab-on-grade or basement homes, we drill a 4- to 6-inch hole through the concrete floor. That hole becomes the suction point. We dig a small pit underneath to create a good air path, then seal the pipe into the concrete. The pipe runs up through an interior closet, garage, or utility room, then exits through the roof.

The fan goes in the attic or on the exterior wall. Attic fans are quieter inside the house but cost more to service later. Exterior fans are easier to replace but can freeze up in extreme cold if not installed with a proper drain. We use the fan model that fits your home's size and soil conditions.

A manometer, a little U-tube gauge, gets mounted on the pipe in your basement or garage. It shows the system is pulling suction. You check it monthly: one side higher means the fan is running. If they level out, the fan has failed and needs replacement.

Crawl space homes are different. Instead of a slab penetration, we lay a heavy-duty vapor barrier over the dirt floor, seal it to the foundation walls and piers, then pull suction from under that membrane. The membrane alone costs $800 to $3,000 depending on the square footage. Full crawl space encapsulation, adding insulation, drainage, and a dehumidifier, runs $1,500 to $15,000. That's a bigger job, but it also solves moisture problems that attract pests and rot.

1. Test the air.Professional test takes two days. If the result is 4.0 pCi/L or higher, you need mitigation.
2. Drill the suction point.A hole through the slab or a sealed membrane under the crawl space.
3. Run the pipe and fan.PVC pipe routes to a fan in the attic or outside, then vents above the roofline.
4. Install the manometer.A simple gauge shows the system is working. Check it once a month.

Why Radon Mitigation matters for your home

Radon is the second leading cause of lung cancer in the U.S., and Madison County has some of the highest radon potential in Alabama. Mitigation drops indoor levels to near outdoor background, which is about 0.4 pCi/L.

The EPA and the U.S. Surgeon General recommend fixing any home that tests at or above 4.0 pCi/L. That's not a suggestion, it's a public health guideline based on decades of research. For smokers, the risk multiplies. For non-smokers, radon is still the leading cause of lung cancer after smoking.

Huntsville's geology is the reason. The Tennessee Valley sits on limestone and shale, which contain uranium. As that uranium decays, radon gas moves up through the soil. Homes with basements are especially vulnerable because the below-grade walls and floor have more contact with the soil. But even slab-on-grade homes can have elevated levels.

A mitigation system also protects your home's resale value. Alabama doesn't require radon disclosure during a home sale, but buyers in Huntsville are increasingly asking for a test. A house with a working system and a post-mitigation test showing low levels is easier to sell than one with a high test result and no fix.

The system itself is low-maintenance. The fan is a wear item that needs replacement every 5 to 10 years. Replacement runs $200 to $600, averaging about $350. Attic and crawl space placements cost more because of access. That's a small cost compared to the health risk.

Madison County is one of 15 Alabama counties with the highest radon potential. Testing is the only way to know your level.

Common problems and what causes them

Most problems come from poor installation: wrong fan size, unsealed cracks, or vent pipes that terminate too low. In Huntsville, heavy clay soil and high water tables can also affect system performance.

The most common mistake is undersizing the fan. A fan that's too weak won't pull enough suction to lower radon levels. A fan that's too strong can pull moisture up from the soil, which leads to mold and musty odors. We match the fan to the soil type and the size of the footprint.

Unsealed cracks and gaps are another issue. If the slab has large expansion joints or a sump pit that's not sealed, the system can't create enough negative pressure to pull gas from the whole area. We seal those openings with polyurethane caulk or a sump cover before we turn on the fan.

Vent pipe termination is critical. The pipe must exit at least 10 feet from any window, door, or fresh air intake, and at least 2 feet above the roofline. If it terminates too low, the radon gets pulled back inside through an open window. That defeats the whole system.

In Huntsville, clay soil can be a challenge. Clay is dense and doesn't let air move easily. Sometimes we need multiple suction points to cover the whole footprint. A high water table can also cause problems, if the soil is saturated, the fan pulls water instead of air, which damages the fan and doesn't lower radon. In those cases, we install a drain tile system or a sump pump to lower the water table first.

Some outfits cut corners by blowing leaves out of the crawl space and calling it done. That's not mitigation. True mitigation requires a sealed system with continuous suction. If a contractor quotes you under $500 for a crawl space fix, they're not doing the full job.

Common questions about Radon Mitigation