Radon Mitigation: What To Expect

What Is Radon Mitigation?

Radon mitigation refers to any process used to reduce indoor radon levels in a home or building. If your radon test results came back at or above 4 pCi/L, the EPA recommends taking action to lower your exposure. The good news: modern mitigation systems are highly effective and can reduce radon levels by 50–99% in most homes.

Mitigation is not a DIY project — it requires a certified radon mitigation contractor who understands your home's foundation type, HVAC system, and the best approach for your specific situation. A poorly installed system can actually increase radon levels or create other issues.

The Most Common Method: Sub-Slab Depressurization (SSD)

Sub-slab depressurization (SSD) is the most widely used and effective radon mitigation method for homes with basement or slab-on-grade foundations. Here's how it works:

1. The contractor drills one or more holes through the concrete floor slab and inserts a PVC pipe into the aggregate or soil beneath
2. The pipe is routed through the home (or around the outside) and terminates above the roofline
3. A radon fan is installed on the pipe to create negative pressure beneath the slab, drawing radon gas out from under the foundation
4. The radon is vented safely to the exterior atmosphere, above the roofline, where it disperses harmlessly

The system runs continuously and quietly. Most homeowners never notice the fan — it sounds similar to a low-level HVAC motor. Energy use is minimal (about the same as a light bulb).

Other Mitigation Techniques

Depending on your home's construction, a contractor may use different or additional approaches:

• Crawl space encapsulation and ventilation — for homes with vented crawl spaces, sealing the crawl space floor with a heavy-duty liner and installing a fan can dramatically reduce radon entry
• Block wall suction — in homes with hollow-block foundation walls, radon can accumulate inside the wall cavities; suction pipes draw it out
• Drain tile suction — if your home has a drain tile system around the foundation, it can be used as part of the mitigation pathway
• Sealing cracks and openings — always done as a supplementary step; not sufficient on its own but improves overall system efficiency
• Heat recovery ventilator (HRV) — increases fresh air exchange in very tight homes; sometimes used in combination with SSD

What Contractors Do: The Installation Process

A typical radon mitigation installation takes 4–8 hours for a standard home. Here's what to expect on installation day:

1. Diagnostic testing to determine how air flows under the slab (suction test)
2. Identification of the best pipe routing — through interior or exterior walls
3. Core drilling through the concrete slab
4. PVC pipe installation from sub-slab to exterior above roofline
5. Radon fan installation (typically in attic, garage, or exterior)
6. Sealing of pipe penetrations and visible cracks in slab
7. System testing and verification
8. Installation of a visual or electronic pressure gauge so you can monitor that the system is operating

Typical Costs

Radon mitigation costs vary based on home size, foundation type, pipe routing complexity, and local labor rates. Here are typical ranges:

Always get at least two quotes. Beware of contractors who quote unusually low prices — quality installation matters for long-term system effectiveness.

Post-Mitigation Retesting: A Critical Step

After your mitigation system is installed, you must retest your home to confirm that radon levels have been reduced to an acceptable level. This is a critical step that some homeowners skip — don't.

Wait at least 24 hours after installation before retesting. Most contractors recommend a short-term test (2–7 days). If levels are still at or above 4 pCi/L, the system may need adjustment — a more powerful fan, additional suction points, or better sealing.