Village, Winnebago County, Illinois
Radon Testing in Winnebago, IL
Updated
IEMA has 255 radon test results on record for Winnebago. 50.6% came back at or above the EPA's action level of 4.0 pCi/L. That is well above the Winnebago County rate of 36.7%. A standard test runs $150 to $300. The only way to know about one specific house is to test it.
About 2,981 people live in Winnebago, a Winnebago County village with roughly 1,180 housing units and a median year built of 1985. It sits near Pecatonica, Rockton and Rockford. It gives its name to the county and sits along the Pecatonica River area.
What IEMA's radon test records show
Look past the median to the tail: 1.2% of Winnebago tests were 20 pCi/L or more, five times the action level. The top reading on record is 38 pCi/L. The average result in Winnebago is 5.45 pCi/L, against 4.23 for Winnebago County overall. IEMA's own dataset covers tests licensed measurement professionals submitted from 2003 through July 2019, keeping only the highest reading on record per address. That means it is not a random sample and not year-by-year, but it is the closest thing to primary local radon data that Illinois publishes.
| Tests | Avg pCi/L | 4+ pCi/L | 10+ | 20+ | |
|---|---|---|---|---|---|
| Winnebago | 255 | 5.45 | 50.6% | 14.1% | 1.2% |
| Winnebago County | 7,642 | 4.23 | 36.7% | 7.9% | 1.1% |
Source: IEMA radon test records, Illinois Emergency Management Agency.
The ground under Winnebago
Winnebago County sits in the Rock River valley of north-central Illinois. Its bedrock is dolomite and limestone left from the Ordovician and Silurian periods, buried under glacial till and outwash the last Ice Age left behind. The EPA places Winnebago County in Radon Zone 1, its highest-potential category: a predicted average indoor screening level at or above 4.0 pCi/L.
Housing in Winnebago
Census Bureau, American Community Survey 2020 to 2024 5-year estimates.
| Homes (housing units) | 1,180 | 125,002 in Winnebago County |
| Median year built | 1985 | 1971 countywide |
| Built before 1980 | 57.6% | 74% countywide |
| Attached (rowhome, townhouse) | 1.2% | 4.3% countywide |
| Mobile homes | 0% | 1.3% countywide |
| Renter-occupied | 13% | 34.1% countywide |
Most of the housing in Winnebago went up between the 1940s and the 1970s (57.6% was built before 1980, median year 1985). That era mostly means poured or block basements, which is the standard layout for a sub-slab test and, if needed, a sub-slab mitigation system.
What we do in Winnebago
Radon testing, Buying or selling a home, and New construction.
Common questions
Is radon a problem in Winnebago?
Yes. Out of 255 IEMA-recorded tests taken in Winnebago, 50.6% came in at 4.0 pCi/L or higher, the EPA's action level. That fits Winnebago County's overall Zone 1 rating, the agency's highest-potential class.
What is the highest radon reading on record near Winnebago?
38 pCi/L, out of 255 IEMA-recorded tests. That is an outlier, not typical, but it shows why testing rather than guessing matters: neighboring houses can differ by a wide margin.
We're closing on a house in Winnebago soon. Is there time to test?
In most cases, yes. Scheduled early in the inspection period, a short-term test (a few days to about a week) has time to come back before you need to decide anything. Details on our <a href="/real-estate-radon-testing">real estate radon testing</a> page.
Nearby
Pecatonica (45.5% of tests at 4+ pCi/L), Rockton (39.2% of tests at 4+ pCi/L), Rockford (36.8% of tests at 4+ pCi/L).
Need radon testing booked in Winnebago?
Tell us why you're testing and any deadline you're working against. You get a fixed price and a straight answer back.