What a radon mitigation system does
A radon mitigation system is a set of pipes and a fan that pulls radon gas from beneath your house and vents it safely outside, above the roofline. The system works by creating negative pressure under your foundation — the fan draws radon-laden air from the soil before it can seep into your living spaces, then exhausts it where it disperses into the outdoor air.
The most common type is called sub-slab depressurization. A pipe is installed through the foundation floor (or sometimes through the basement wall), connected to a fan mounted in the attic or outside, and vented above the roofline. The fan runs continuously or on a timer. A second type, crawl space depressurization, works the same way but pulls from under a crawl space instead of a sealed basement.
Radon levels are measured in picocuries per liter (pCi/L). The U.S. Environmental Protection Agency (EPA) recommends taking action if your test result is 4 pCi/L or higher. A mitigation system can reduce radon levels by 50 to 99 percent, depending on the system design and your home's construction.
Key Takeaways
- Radon mitigation systems use a fan and ductwork to pull radon from beneath your foundation and vent it outside above the roofline.
- Sub-slab depressurization is the most common method and works in basements; crawl space depressurization is used when there is no basement.
- Installation typically costs between $800 and $2,500, depending on your home's layout and whether the contractor needs to drill through concrete.
- The system requires a power outlet and produces a small amount of noise; the fan should run continuously to maintain effectiveness.
- Post-installation testing should occur 24 hours after the system is turned on to confirm radon levels have dropped below 4 pCi/L.
How the installation process works
A radon contractor will first inspect your basement or crawl space to decide where to place the intake pipe and where to route the exhaust vent. They look for the best location to drill through the foundation — usually a spot away from windows, doors, and HVAC returns so the vented radon does not re-enter the house.
The contractor drills a hole through the foundation floor or wall, inserts a PVC or ABS plastic pipe, and seals the opening with caulk or foam. The pipe runs upward through the house (usually inside a wall or along the exterior) to the attic or outside, where it exits above the roofline — typically 10 to 12 inches above the highest point of the roof. A fan unit is mounted somewhere along this ductwork, most often in the attic or on an exterior wall.
The fan is wired to a dedicated electrical outlet or hardwired to your home's electrical panel. A manometer — a small gauge that measures pressure — is installed on the ductwork so you can see whether the system is running. Installation usually takes one to three days, depending on your home's size and complexity.
Cost and what affects the price
Radon mitigation system installation typically ranges from $800 to $2,500. The cost depends on several factors: whether you have a basement or crawl space, how deep the foundation is, whether the contractor needs to drill through concrete or another material, how far the ductwork must travel, and whether the fan can be mounted in the attic or must be placed outside.
Homes with finished basements or complex layouts may cost more because the contractor has to route the pipe through walls or around obstacles. If you need a second intake point (sometimes recommended for larger homes or those with multiple foundation sections), the cost increases. Some contractors charge a flat fee; others charge by the hour or by the complexity of the job.
The fan itself uses electricity continuously, which adds to your utility bill. A typical radon fan draws 100 to 150 watts and costs roughly $10 to $20 per month to run, depending on your local electricity rates.
Noise and what to expect after installation
A radon mitigation fan produces a low humming sound, usually between 50 and 60 decibels — roughly the volume of a quiet conversation. If the fan is mounted in your attic, you may hear it faintly from rooms below. If it is mounted on an exterior wall, the noise is mostly outside. Some homeowners notice the sound at first and then stop hearing it; others find it bothersome and ask the contractor to add sound-dampening material around the fan.
After installation, the system should run continuously to maintain effectiveness. Some systems have a timer that allows you to turn the fan off during certain hours, but this reduces how much radon is removed. The manometer on the ductwork shows whether the system is operating — the needle should move when the fan is on.
You should have your radon levels tested again 24 hours after the system is turned on. This post-mitigation test tells you whether the system is working well enough. If levels are still above 4 pCi/L, the contractor may need to adjust the system or add a second intake point.
Maintenance and long-term operation
Radon mitigation systems require minimal maintenance. The fan should be inspected once a year to make sure it is running and the ductwork is clear of debris. You can do a visual check yourself: look at the manometer to confirm the needle moves when the fan is on, and listen for the fan sound. If the needle does not move or you hear no sound, the fan may have stopped working.
The fan itself typically lasts 5 to 10 years before it needs to be replaced. Replacement fans cost $300 to $600, plus labor. The ductwork and seals can last much longer if they are not damaged. If you see cracks in the foundation or water seeping in, have the contractor inspect the system to make sure the seals are still intact.
If you plan to sell your home, disclose the radon mitigation system to the buyer. Many buyers view an existing system as a positive — it shows the problem has been addressed. Some states require radon testing before a home sale; check your state's real estate disclosure laws.
When a mitigation system may not be enough
In rare cases, a single mitigation system does not reduce radon levels below 4 pCi/L. This can happen in homes with multiple foundation sections, very high radon levels, or soil conditions that make depressurization less effective. The contractor may recommend a second intake point, a larger fan, or a combination system that includes both sub-slab and crawl space depressurization.
Sealing cracks and gaps in the foundation can also help, though sealing alone is not usually enough to meet EPA recommendations. Sealing is often done alongside mitigation to improve the system's efficiency. Improving ventilation in your basement or crawl space — by opening windows or installing a ventilation fan — can lower radon levels slightly, but again, this is not a substitute for a mitigation system.
Comparing mitigation to other radon reduction methods
| Method | How it works | Typical cost | Effectiveness |
|---|---|---|---|
| Sub-slab depressurization | Fan pulls radon from under foundation and vents it outside | $800–$2,500 | 50–99% reduction |
| Crawl space depressurization | Fan pulls radon from under crawl space and vents it outside | $800–$2,500 | 50–99% reduction |
| Foundation sealing | Caulk or foam seals cracks and gaps in foundation | $300–$800 | 10–30% reduction |
| Basement ventilation | Fan or open windows increase air circulation | $200–$600 | 5–20% reduction |
Frequently Asked Questions
Can I install a radon mitigation system myself?
You can do some of the work — drilling the hole, running the pipe, and mounting the fan — but most homeowners hire a contractor. The EPA maintains a list of certified radon contractors by state. A contractor knows local building codes, can may support the vent is placed correctly to avoid re-entry, and can test the system after installation to confirm it works.
Will a radon mitigation system increase my heating and cooling costs?
The fan itself uses about $10 to $20 per month in electricity. A properly installed system should not significantly affect your heating or cooling costs because the ductwork is sealed and the system does not introduce outside air into your home — it only removes radon from beneath the foundation.
What if my radon levels are still high after mitigation?
Post-mitigation testing should happen 24 hours after the system is turned on. If levels are still above 4 pCi/L, contact the contractor. They may need to add a second intake point, upgrade the fan, or adjust the system design. Some homes require more aggressive mitigation than others.
Do I need to do anything to maintain the system?
Check the manometer once a month to confirm the fan is running, and have the system inspected annually. Listen for the fan sound and look for any visible damage to the ductwork. The fan typically lasts 5 to 10 years and will need to be replaced when it stops working.
Can I turn off the radon mitigation system in winter or summer?
The system should run continuously for best results. Some systems have a timer, but turning the fan off reduces how much radon is removed. If you turn it off, radon levels will begin to rise again. Running the fan year-round is the most effective approach.