Lafayette County, WI: EPA's radon zone, explained

EPA places Lafayette County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Rank it against the rest of the country and Lafayette County lands in the 80th percentile for radon potential.

How Lafayette County compares

Lafayette County, Wisconsin is home to about 17,306 people across 633.588 square miles. Population density there runs about 27 people per square mile. By population, Lafayette County is the 611th largest of every county sharing its EPA zone — the 43rd percentile by population within that zone. Geologically, Lafayette County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

What this actually means for a house in Lafayette County

Lafayette 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. A Zone 1 rating means testing is worth doing sooner rather than later, but it is still county-wide average, not a reading for any single house — some homes in Lafayette County will test well under the action level, and EPA's guidance is to test regardless of zone.

If Lafayette County tests above the action level

For a Lafayette County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Wisconsin's state radon program

For Lafayette County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Lafayette County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

Where Lafayette County's figures come from

Lafayette County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.