A high radon test is common news in Johnson County. Iowa has the highest average indoor radon levels in the country, roughly 7 in 10 Iowa homes test at or above the EPA action level of 4.0 pCi/L, and our county sits in EPA Radon Zone 1. The good news is just as clear: radon is one of the most fixable problems a house can have.
The fix is a mitigation system, and in almost every home that means active sub-slab depressurization, or ASD. It is a straightforward piece of equipment: a suction point under your foundation, a run of PVC pipe, and a quiet inline fan that pulls radon out of the soil and releases it harmlessly above your roofline. Most installations take a single day, and homes that started well above 4.0 typically retest under 2.0 pCi/L afterward.
We design and install mitigation systems throughout Iowa City, Coralville, North Liberty, Tiffin, Solon, University Heights, and the rest of Johnson County.
What a Mitigation System Actually Is
Radon enters your home because the air pressure inside is usually lower than the pressure in the soil beneath it, so gas gets drawn up through sump pits, floor drains, slab cracks, and crawl spaces. An active sub-slab depressurization system reverses that relationship. Instead of your house pulling soil gas in, the system pulls it out from under the foundation before it ever reaches your living space.
The whole thing has three working parts: a suction point drilled through the slab into the soil below, a sealed pipe run carrying the gas up and out, and an inline radon fan that runs continuously to keep the soil under your home at lower pressure than the house. There is no filter to replace, no chemical, no ductwork into your living space. It is a small, dedicated exhaust system for the ground your house sits on.
Because the gas comes from uranium decaying in the glacial soils under all of Iowa, the source never goes away. The system does not try to eliminate radon from the soil; it just makes sure the gas takes the pipe instead of your basement.
How It Works, Step by Step
First, the suction point. We core a hole roughly the size of a coffee can through the basement slab, remove a small amount of soil or gravel beneath it to create a collection pit, and seat a PVC pipe into the opening, sealed airtight against the concrete. Diagnostics confirm air moves under the whole slab from that one point, so the system treats the entire footprint.
Next, the pipe routing. From the suction point, the pipe runs up and out of the house, either through the rim joist to an exterior wall run, or up through a closet, garage, or utility chase for a tidier interior route. We plan the route with you before we drill anything.
Then the fan and discharge. The inline radon fan mounts outside the living space, in the attic, the garage, or on the exterior run, never in the basement, so any leak on the pressurized side stays out of your air. Above the fan, the pipe continues until it discharges above the eave, where the exhaust disperses safely away from windows and doors. Finally, we mount a u-tube manometer on the pipe in the basement: a simple liquid gauge that shows at a glance the fan is pulling suction.
What Installation Day Looks Like
Most installations are done in one working day. We show up in the morning, confirm the routing plan we walked through at the quote, and protect the work areas. The loudest part is coring the slab, which takes a few minutes; the rest is pipe fitting, sealing, and electrical for the fan circuit.
Along the way we seal the obvious entry points that would otherwise let the system pull conditioned air from your basement instead of soil gas: gaps around the suction pipe, accessible slab cracks, open sump lids, and utility penetrations. Sealing alone will not fix radon, but it makes the fan's job easier and the system more efficient.
By the time we leave, the fan is running, the manometer shows steady vacuum, and your basement looks the way we found it apart from one labeled white pipe. We walk you through what the gauge should read and leave documentation of the whole system, which matters later because Iowa Code chapter 136B requires sellers to disclose radon test results and mitigation work when a home changes hands. A documented, professionally installed system is a selling point, not a stigma.
System Design for Iowa City's Mix of Homes
Johnson County housing runs from pre-war homes near downtown, the Northside, and Longfellow to brand-new construction in North Liberty and Tiffin, and the right system design depends on what is under the house. A standard basement slab gets the classic setup described above, though older slabs poured in sections or over dense clay sometimes need a second suction point to treat the whole footprint.
Crawl spaces get a different approach. We lay a durable membrane over the exposed soil, seal it at the walls and seams, and draw suction from beneath the membrane, a method called sub-membrane depressurization. It often improves moisture and musty-air problems as a side benefit.
Sump pits deserve special mention because they are everywhere in Iowa City basements and they are one of radon's favorite doorways. In many homes the sump basin doubles as the ideal suction point: we fit a sealed, gasketed lid over the pit and pull suction directly from it, treating the drain tile loop around your entire foundation as a ready-made collection network. Homes with mixed foundations get a combined system with the fan sized for both.
Results You Can Verify, Not Just Take on Faith
A mitigation system is only as good as the retest that follows it. After installation, once the system has run long enough to stabilize, we perform a follow-up measurement with a continuous radon monitor under standard closed-house conditions to document your new level. Mitigated homes typically read under 2.0 pCi/L, well below the EPA action level of 4.0.
You also get a permanent, glanceable check: the u-tube manometer on the system pipe. If the two liquid columns are offset, the fan is pulling suction. If they ever level out, the fan has stopped and it is time to call us. We recommend glancing at it when you change furnace filters and running a fresh radon test every two years to confirm the number is holding.
For Iowa City landlords, that verification is not optional. The city's rental ordinance, in effect since July 1, 2021, requires mitigation for single-family and duplex rentals that test at 4.0 pCi/L or higher during the permit cycle, with results documented. We install to that standard and provide the paperwork the permit process expects.
What It Costs to Own and Run
A typical mitigation system installation in the Iowa City area runs $900 to $1,400. Where a specific home lands in that range depends on foundation type, the number of suction points, pipe routing, and whether a crawl space membrane is involved. We quote a firm price after seeing the house, and the quote is the price.
Operating costs are modest. The inline fan draws about as much electricity as a light bulb, which works out to a few dollars a month, and it runs continuously by design. There is nothing to refill, empty, or clean. Radon fans commonly last ten years or more, and replacement is a straightforward swap when the time comes.
Compare that to the alternative. Radon is the second-leading cause of lung cancer overall, the leading cause among people who have never smoked, and the EPA attributes about 21,000 U.S. lung cancer deaths per year to it. Around $1,000 once and pocket change monthly is a small price for taking that off the table in a Zone 1 county.
Why Certification Matters in Iowa
Iowa does not treat radon work as a handyman task. Anyone performing radon mitigation professionally in this state must be certified through the Iowa state radon program run by the Iowa Department of Health and Human Services. That certification is your assurance that the installer understands system diagnostics, fan sizing, discharge requirements, and the measurement standards used to verify the result.
It matters practically, too. Iowa City rental permits, real estate disclosures under Iowa Code chapter 136B, and any future sale of your home all go smoother with a system installed and documented by a certified professional. An uncertified install that vents at ground level or dumps radon into an attic is not a bargain; it is a redo.
If your home has tested high, or you have a rental permit deadline coming, call us or send the form on this page. We will look at your foundation, quote you a firm price, and in most cases have the number under 2.0 within days of the install.