How to mitigate radon

Poured-concrete basement with good sub-slab aggregate is the simplest install — one suction point through the slab, sealed PVC riser, exterior fan. Slab-on-grade homes need careful suction-point siting because there is no basement to route through. Crawlspaces need a sealed membrane (encapsulation) tied into the suction system. Fieldstone or rubble foundations cannot be depressurized at the slab — they require a different approach, usually block-wall depressurization or full crawlspace encapsulation, and cost roughly 1.5–2x a standard install.

A single 4-inch suction point covers most homes up to about 2,000 sqft of slab if the sub-slab aggregate communicates well. Larger footprints, slabs poured in sections, or homes with interior footings that block airflow under the slab need additional suction points. Each additional point adds roughly $300–600 — pipe, coring, sealant, and labor.

Code (ANSI/AARST RMS-SF 2023) requires the fan to be outside the conditioned envelope — exterior wall, attic, or garage, never in a basement or living space. A clean exterior run up the side of the house is the cheapest and most accessible. Routing through an interior chase, up through closets, and out through the roof is more labor and looks better but adds $400–900. Aesthetics matter more on the front elevation than the back.

An open sump pit is a giant radon entry point. If you have one, it must be sealed with an airtight cover (gasketed, with grommets for the pump cord and discharge line) and tied into the mitigation system. Done right, your sump pit becomes a free second suction point. Done wrong, your sump pump fails because the cover blocks float-switch access. Confirm the mitigator uses a serviceable cover with a removable inspection port.

Short-term charcoal kits ($15–35) are cheap, mailed in, and adequate for a baseline screening — but they are vulnerable to "closed-house" violations and weather swings. Continuous radon monitors (CRMs) deployed for 48+ hours by a certified tester ($150–300) give you hour-by-hour readings, tamper detection, and a defensible result for real estate transactions. For any home where you are deciding whether to mitigate, the CRM test is worth it.

A legitimate install includes a post-mitigation short-term test 24 hours to 30 days after the fan is energized. EPA action level is 4 pCi/L; the practical mitigation target is below 2 pCi/L. If the post-test comes back at 3.5 pCi/L, technically you are "under the action level" but the system is underperforming and the mitigator should adjust (add a suction point, swap to a higher-static-pressure fan) at no charge.

RadonAway RP series and Festa AMG series are the industry standards. Fan model is sized to the suction needed (RP145 for tight slabs, RP265 for loose aggregate, larger for crawlspaces). A correctly sized and properly isolated fan is barely audible from inside. Vibration coming through the riser into the living space means the fan is rigidly coupled to the PVC — a soft rubber coupling at the fan inlet and outlet fixes it.