The Most Effective Way to Lower Radon
The gold standard for reducing indoor radon is active sub-slab depressurization (SSD) — commonly called a radon mitigation system. A certified contractor inserts a PVC pipe through the concrete slab or foundation and connects it to a continuously running fan. The fan creates negative pressure beneath your home, drawing radon gas out before it can enter your living space and venting it harmlessly outside.
When properly installed, SSD systems typically reduce radon levels by 50 to 99%. Most homes with levels as high as 20–30 pCi/L can be brought below the EPA action level of 4 pCi/L — often well below 2 pCi/L — with a single system.
The Methods, Ranked by Effectiveness
- Active sub-slab depressurization (SSD): 50–99% reduction. The best and most reliable method.
- Drain tile depressurization: Effective alternative for homes with perimeter drain tiles.
- Sub-membrane depressurization (crawlspaces): Required for crawlspace foundations.
- Increased ventilation / house pressurization: Temporary and unreliable for Maine winters.
- Sealing cracks and openings: Helpful as a complement, not a standalone fix.
Method 1: Active Sub-Slab Depressurization (Most Homes)
This is the most commonly used method because it works for the vast majority of Maine homes with basement or slab-on-grade foundations. Here's how it works step by step:
Diagnostic Assessment
A certified mitigator inspects your home's foundation, checks communication between suction points, and reviews your radon test results to design the right system.
Core Drilling and Pipe Installation
A hole is drilled through the concrete slab. A PVC pipe is inserted and routed through the home (usually up through interior living space or along an exterior wall) to an exit point above the roofline.
Fan Installation
A radon-specific fan is attached to the pipe, usually in an unconditioned space like a garage or attic, or on the exterior. The fan runs continuously at low cost (typically $5–$15/month in electricity).
Follow-Up Testing
A post-mitigation test is conducted 24–30 days after installation to verify that levels have dropped to safe levels. Most systems achieve results below 2 pCi/L.
Method 2: Crawlspace Mitigation
Homes with crawlspace foundations require a different approach: sub-membrane depressurization. A heavy-duty polyethylene vapor barrier is laid across the crawlspace floor and sealed to the foundation walls. A pipe and fan draw radon out from beneath the membrane.
This method addresses two problems at once: radon entry and moisture intrusion. Many crawlspace homes in Maine benefit significantly from encapsulation, which also improves overall indoor air quality and reduces heating costs.
Learn more about our crawlspace vapor barrier and encapsulation services.
Method 3: Sealing Entry Points
Sealing cracks in the foundation, gaps around pipes, and other openings can modestly reduce radon entry. However, EPA research shows that sealing alone rarely reduces radon levels enough to reach safe thresholds — primarily because radon can still diffuse through porous concrete and through soil entry points that are difficult or impossible to seal completely.
Sealing is best used as a complement to active depressurization, not a replacement. Many mitigators will seal obvious cracks during installation to improve the overall system efficiency.
Foundation crack sealing is particularly valuable when combined with mitigation — see our epoxy crack sealing service for details.
Method 4: Increasing Ventilation
Opening windows and increasing airflow can temporarily dilute radon concentrations. This may work in mild climates or temporarily during warm months, but it is not a reliable long-term solution for Maine homeowners. Maine winters demand tight, well-insulated homes — the kind of home where radon accumulates most readily.
Heat Recovery Ventilators (HRVs) are sometimes used to introduce fresh air without wasting heat. While HRVs can modestly reduce radon levels, they rarely achieve the dramatic reductions of an active depressurization system, and they are expensive to install and maintain.
What About Radon in Water?
If your home has well water with elevated radon, the primary solution is an aeration system — a device that bubbles air through the water to drive off dissolved radon before it reaches your taps. Activated carbon filters are another option for lower levels.
Treating water radon is a separate step from treating air radon. If your home uses a private well, it's worth testing the water as well as the air, especially if air levels are elevated even after installing a standard SSD system.
Learn about our radon-in-water treatment services.
How Long Does it Take to Lower Radon Levels?
Once a mitigation system is operating, radon levels begin dropping within hours. However, radon test results are measured over time (typically 48-hour short-term tests or 90-day long-term tests), so you won't see confirmed numbers immediately. Most contractors recommend a post-mitigation test starting 24 hours after system activation, run for at least 48 hours.
Can Radon Come Back After Mitigation?
A properly installed and maintained mitigation system continues working indefinitely. The fan is the only moving part and typically lasts 5–10 years before needing replacement (a straightforward repair costing $150–$300). The pipe and connections are permanent.
You should test your home every two years to confirm the system is still working effectively, especially if you make any significant renovations, seal the basement, or notice the system fan indicator light has changed.
Ready to Permanently Fix Your Radon Problem?
Central Maine Radon & Water Mitigation installs proven sub-slab depressurization systems across Central Maine. Most jobs are completed in a single day.
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