Radon mitigation is the engineered process of reducing indoor radon gas to safe levels — typically below the EPA's 4.0 pCi/L action level, and ideally well below 2.0 pCi/L. In Cincinnati and the surrounding metro, where roughly one in three tested homes exceeds the action level, mitigation is one of the highest-leverage things you can do for your family's long-term health.
The technique we use almost universally in the Cincinnati area is called sub-slab depressurization (SSD), also known as active soil depressurization. It's the EPA-recommended approach and reduces radon by up to 99% in most homes when installed by a licensed mitigator.
What is radon mitigation?
Radon is a colorless, odorless radioactive gas produced by the natural decay of uranium in the soil and bedrock under your house. In Cincinnati, the Ordovician limestone and shale beneath the region is uranium-rich, which is why our metro consistently tests so high. Mitigation doesn't stop radon from being produced — that would be impossible. Instead, it intercepts the gas before it enters your home and vents it safely outside.
A properly installed mitigation system has four core parts:
- A suction point — a hole drilled through the concrete slab (or under a crawl space membrane) where a pipe is set
- A vertical PVC pipe — routed up through the home (or along the exterior) to above the roofline
- An in-line radon fan — usually attic-mounted or exterior-mounted, that creates negative pressure under the slab
- A manometer — a simple U-tube pressure gauge that lets you see at a glance whether the system is working
Sub-slab depressurization: the gold standard
SSD works by reversing the pressure gradient that causes radon to enter your home in the first place. Without a system, your house operates at slightly negative pressure relative to the soil — especially in winter, when warm air rising creates the "stack effect" — which pulls radon gas up through cracks, sump pits, plumbing penetrations, and porous concrete.
An SSD system flips that gradient. The fan continuously pulls air from beneath the slab and vents it above the roof. Because air pressure under the slab is now lower than the pressure inside the home, radon can no longer enter — it goes up the pipe and harmlessly disperses into the atmosphere outside.
Why exterior fan placement matters
Any active soil depressurization system has the fan installed in an unconditioned space — either an attic, garage, or outside the building. This is required by code: if the fan ever develops a leak in the pressurized section, it must not discharge into a living space. Avoid contractors who mount fans in basements or finished mechanical rooms.
The mitigation process — step by step
1. Site evaluation (15-30 minutes)
Our partner technician walks the home: foundation type, sump pit location, drainage characteristics, and where the pipe can be routed. They identify the optimal suction point and the cleanest path for the vertical pipe to the roof.
2. Sealing radon entry points (30-60 minutes)
Visible cracks, gaps around plumbing penetrations, sump pits, and any other obvious radon entry routes are sealed with polyurethane caulk or sump-pit covers. This isn't a mitigation method on its own, but it improves system performance.
3. Suction point installation (1-2 hours)
A 4-5" hole is cut through the concrete slab. About a cubic foot of soil is excavated beneath to create a small "communication chamber" that allows the fan's suction to spread effectively under the entire slab.
4. Pipe routing (1-2 hours)
Schedule 40 PVC pipe is run from the suction point, up through the home or along an exterior wall, terminating at least 12 inches above the roofline and 10 feet from any window or air intake. Interior routes are cleaner aesthetically; exterior routes are simpler and cheaper but less visually subtle.
5. Fan installation
An in-line radon fan (typically a Festa AMG or RadonAway brand) is installed in the pipe in an attic or outside the home. The fan runs continuously, draws less power than a 75-watt bulb, and typically lasts 10-15 years.
6. Manometer and labeling
A pressure gauge is installed visibly on the pipe so you can monitor system function at a glance. The system is labeled with installer info and current radon level.
7. Post-mitigation testing (48-72 hours after install)
A short-term test confirms the system has reduced radon below 4.0 pCi/L. Most properly installed systems get homes well under 2.0 pCi/L — often under 1.0.
How long does a mitigation system last?
The structural components — pipe, suction point, sealant — typically last the life of the home. The fan is the only consumable: most run 10-15 years before needing replacement. Replacement is a 30-minute job and usually runs $300-500 including parts.
We recommend retesting your home every two years, after any significant foundation work, and any time the manometer reading changes noticeably from its baseline.
Radon mitigation cost in Cincinnati
Most Cincinnati-area mitigation projects run $900 to $1,600 for a standard basement system. Crawl space homes or homes requiring multiple suction points may cost $1,200 to $2,200. Key cost drivers:
- Foundation type (slab is usually cheapest, crawl space and combination foundations cost more)
- Interior vs. exterior pipe routing
- Whether sealing is needed
- Roof type and pipe termination requirements
- Distance from the suction point to the fan location
We provide fixed-price quotes — not hourly estimates that can balloon. See a full breakdown of pricing factors or request a free quote.