Types of Radon Mitigation Systems: SSD, SMD, and More

Not all radon mitigation systems are the same. The right approach depends on your home’s foundation type, construction details, and the severity of the radon problem. Here’s a breakdown of the most common systems and when each one makes sense.

Sub-Slab Depressurization (SSD)

SSD is the most widely installed radon mitigation method and works in homes with basement or slab-on-grade foundations. A hole is drilled through the concrete slab, and a PVC pipe is inserted into the aggregate or soil below. An inline fan draws radon-laden air from beneath the slab and exhausts it above the roofline, where it disperses harmlessly.

SSD works by creating a slight negative pressure under the foundation, preventing radon from entering through cracks and openings. It’s effective, reliable, and typically the most affordable option. Most homes need just one suction point, though larger or compartmentalized foundations may require two or more.

Sub-Membrane Depressurization (SMD)

SMD is the standard approach for homes with dirt-floor crawl spaces. A durable polyethylene vapor barrier is laid over the exposed soil and sealed to the foundation walls. A suction pipe and fan system then draws radon from beneath the membrane and vents it outside.

The vapor barrier also reduces moisture and improves crawl space air quality, making SMD a dual-purpose upgrade. Proper sealing at all edges, piers, and penetrations is critical — gaps in the membrane will reduce the system’s effectiveness.

Drain Tile Suction

If your home has an existing perimeter drain tile system (interior or exterior), a mitigation contractor can sometimes tap into it as a suction point. This approach avoids drilling through the slab and can provide excellent coverage since drain tiles run along the entire foundation perimeter. Not all drain tile systems are suitable — the tiles need to be connected and have adequate airflow for this method to work.

Which System Is Right for Your Home?

The foundation type is the primary deciding factor. Basements and slabs get SSD. Crawl spaces get SMD. Homes with both (a common setup) may need a combination. An experienced radon mitigator will run a diagnostic pressure test to determine how many suction points are needed and where to place them for maximum coverage.

Regardless of system type, a properly installed mitigation system should reduce radon levels by 80% to 99%. Post-installation testing confirms the system is performing as expected.

Find certified radon mitigation contractors in your area to determine the best system for your home.