What EPA's radon map says about Winnebago County

Winnebago County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Rank it against the rest of the country and Winnebago County lands in the 76th percentile for radon potential.

Winnebago County by the numbers

About 10,383 people live in Winnebago County, Iowa, spread over 400.489 square miles. Averaged across its land area, Winnebago County runs about 26 people per square mile. Among counties sharing Winnebago County's EPA zone, it outranks 29% of them by population. EPA's geology-based Region 7 groups Winnebago County with 411 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Winnebago County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. Being in Zone 1 raises the odds Winnebago County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

If Winnebago County tests above the action level

Mitigation cost doesn't depend on Winnebago County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Iowa's state radon program

Winnebago County's test kit answers today; a Airthings radon monitor keeps answering for Winnebago County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Winnebago County's numbers. Whatever zone Winnebago County carries, the zone explainer covers what it does and doesn't tell you about any one house.