Grundy County, IA radon potential
Grundy County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. That puts Grundy County in the 77th percentile nationally for radon potential — higher than 77% of the counties EPA has rated.
Grundy County by the numbers
Grundy County, Iowa is home to about 12,405 people across 501.855 square miles. Population density there runs about 25 people per square mile. Within its own EPA zone, Grundy County is bigger by population than 33% of the counties that share it. Geologically, Grundy County is grouped into EPA Region 7 alongside 411 other counties that share its rock and soil setting.
Why the zone isn't the answer by itself
Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Grundy County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Being in Zone 1 raises the odds Grundy 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 Grundy County tests above the action level
A short-term test kit is the standard first step and typically costs far less than mitigation itself. If a test comes back at or above 4 pCi/L, a radon mitigation system for a typical home runs roughly $800–$2,500 (around $1,200 for a common single-family install), driven mainly by foundation type, not by county.
Find Iowa's state radon program
For Grundy County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Grundy County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.
Where Grundy County's figures come from
The methodology guide shows exactly which EPA and Census sources feed Grundy County's numbers. Whatever zone Grundy County carries, the zone explainer covers what it does and doesn't tell you about any one house.