Radon remediation is the process of reducing radon gas concentrations inside a building, typically by drawing the gas from beneath the foundation and venting it safely outdoors. The EPA recommends remediation when indoor radon levels reach 4 pCi/L (picocuries per liter) or higher, and suggests homeowners consider it even at levels between 2 and 4 pCi/L, since there is no known safe level of radon exposure.
Why Radon Needs Active Removal
Radon is a naturally occurring radioactive gas that seeps up from the ground through cracks in foundations, gaps around pipes, and porous concrete. It’s colorless and odorless, so the only way to detect it is with a test. Once trapped indoors, radon decays into radioactive particles that lodge in lung tissue when inhaled, making it the leading cause of lung cancer among nonsmokers.
Simply sealing cracks in your foundation isn’t enough. Studies show that sealing alone reduces radon by roughly 50% at best, and the results are unreliable, especially in warmer months when pressure differences between indoor and outdoor air shift. Sealing does matter, but only as a supporting step. It makes mechanical systems work more efficiently by limiting the number of pathways radon can use to enter your home.
How Active Soil Depressurization Works
The most common and effective method is called active soil depressurization, or ASD. A contractor drills a hole through your basement floor or slab and digs a small suction pit in the soil or gravel underneath. A PVC pipe runs from that pit up through the house (or along an exterior wall) and exits above the roofline. A fan mounted in an unconditioned space like an attic or garage pulls air continuously from beneath the foundation, carrying radon gas up and out before it can enter your living space.
The fan can’t be installed in or below a livable area of the home, because any leak would push radon into the very rooms you’re trying to protect. The exhaust pipe must terminate at least 10 feet above ground level, 10 feet from any windows or doors, and above the edge of the roof. These clearances prevent the vented gas from being pulled back inside.
A small U-tube gauge (a simple liquid-filled tube mounted on the pipe) gives you a visual indicator that the fan is creating suction. Some systems also include an active monitor that sounds an alarm if the fan fails.
How Effective These Systems Are
ASD systems are remarkably effective. A Health Canada field study of 52 homes found an average radon reduction of 90.7%, with a median of 93.5%. The best-performing installations cut radon by 99.6%. Even the lowest performer in that study achieved a 47% reduction, and that’s an outlier. The World Health Organization puts the typical range for active ventilation systems at 90 to 98% reduction.
When sealing is combined with active depressurization, results improve further. One Austrian study documented a 99% reduction using this combined approach. The takeaway is straightforward: the fan does the heavy lifting, and sealing supports it.
Crawlspaces and Different Foundation Types
Not every home sits on a concrete slab, and the remediation approach changes depending on your foundation. For homes with basements or slab-on-grade foundations, sub-slab depressurization (the system described above) is the standard. Variations exist for homes with drain tile systems or sump pits, where the suction pipe connects to existing drainage infrastructure instead of a new hole in the slab.
Crawlspaces require a different technique. If the crawlspace has a concrete floor, sub-slab suction still works. But if it has a dirt floor, the contractor installs what’s called sub-membrane depressurization. A thick plastic sheet is laid over the exposed earth and sealed tightly to the crawlspace walls, foundation piers, and any penetrations. The fan and piping system then draws radon from under the membrane and vents it outside, just like a sub-slab system. The membrane essentially creates an artificial slab for the suction to work against.
Ventilation-Based Systems
In some homes, particularly those with tight construction and good insulation, a heat recovery ventilation system (HRV) can reduce radon by increasing the exchange of indoor and outdoor air. These systems bring in fresh air while recovering heat from the outgoing exhaust, so energy costs don’t spike dramatically. A Swedish study on a detached house found that an HRV system brought radon levels down from around 600 Bq/m³ to below 100 Bq/m³, well under the EPA’s action level.
HRV systems also help balance indoor air pressure. Homes with negative pressure (where indoor air pressure is lower than the pressure in the soil) essentially vacuum radon in through the foundation. By balancing that pressure, ventilation systems reduce the driving force that pulls radon inside. These systems are less common than ASD for radon specifically, but they’re a practical option when soil depressurization is difficult to install or when a home already has an HRV for general air quality.
What Installation Looks Like
Most ASD installations take a single day. A certified contractor will assess your foundation type, identify the best suction point, and route the pipe in the least visually intrusive way possible. Interior pipe runs typically go through closets, utility rooms, or garage corners. Exterior runs are mounted to the side of the house and painted to match.
Costs vary by region and home complexity, but a typical residential installation runs between $800 and $2,500. Homes with multiple foundation types (say, a partial basement and a crawlspace) or unusual layouts may cost more because they need additional suction points.
Look for a contractor certified through the National Radon Proficiency Program (NRPP), which is accredited under international standards and recognized by the EPA. NRPP-certified professionals must demonstrate competence every two years and follow published national standards for installation. Several states require this certification by law.
Maintenance and Ongoing Costs
Once installed, an ASD system requires very little attention. The fan runs continuously and uses about as much electricity as a standard light bulb. Fans typically last five or more years, though manufacturer warranties tend to cap at five. Replacing one costs roughly $200 to $350 including labor.
Your main job is checking the U-tube gauge periodically to confirm the system is still creating suction. If the liquid levels are equal on both sides, the fan has stopped working and needs attention. Systems with active monitors make this even easier by alerting you automatically.
Testing After Installation
A post-installation radon test should be done within 30 days of the system going live, but no sooner than 24 hours after the fan starts running. This gives the system time to draw down the radon that’s already accumulated in the soil gas beneath your home. Short-term test kits work for this initial check, but a longer test of 90 days or more gives a more accurate picture of your year-round exposure.
After that initial confirmation, the EPA recommends retesting at least every two years. Radon levels can shift over time as soil conditions change, the foundation settles, or the fan degrades. A two-year testing cycle catches any creep before it becomes a meaningful exposure risk.