Guide
Does Illinois Require Radon-Resistant New Construction?
Updated
Yes. Since 2013, Illinois's Radon Resistant Construction Act (420 ILCS 52/, effective June 1, 2013) has required new single-family homes and dwellings with two or fewer units to include passive radon-resistant construction techniques. "Passive" means the vent piping is built in during construction but no fan runs yet; testing after the home is enclosed tells you whether the passive system alone is enough.
What the law actually covers
The Radon Resistant Construction Act applies to new single-family residential construction and dwellings containing two or fewer apartments, condominiums, or townhouses. It cites radon as the leading cause of lung cancer among non-smokers (the Act's own findings reference the Harvard School of Public Health, Center for Risk Analysis) as its basis. Local jurisdictions, like Madison County's 2016 notice to builders, implement and enforce it through the building permit process, requiring the architectural drawings for a passive control system as part of new-construction permit applications.
Passive vs. active: what "radon-resistant" actually means
A passive system is the required minimum: a sealed vent pipe run from beneath the slab or crawl space up through the roofline, with no fan, relying on natural stack effect to carry gas out. It is not the same as an active mitigation system (also called active soil depressurization), which adds a continuously running fan and is what gets installed after a high test result. The 2021 edition of the national model code (IRC) also added a requirement, where jurisdictions adopt that appendix, for post-construction radon testing and mitigation if levels come back high.
Why testing a new home still matters
A passive system reduces radon on its own in many homes, but not always enough on its own to get below the EPA's 4.0 pCi/L action level. The only way to know whether a specific new home's passive rough-in is sufficient, or whether it needs a fan added to become active, is a test after the home is fully enclosed.
Quick answers
FAQ
Does every new home in Illinois get an active mitigation system?
No. The state requirement is for passive radon-resistant construction (the vent piping, no fan) as a baseline. A fan gets added only if testing shows the passive system isn't keeping levels low enough on its own.
Does this apply to a home I'm buying that was built years ago?
The 2013 law applies to new construction going forward from its effective date; it doesn't retroactively require older homes to be retrofitted. An older home can still be tested and mitigated the same way regardless of when it was built.
Who enforces the radon-resistant construction requirement?
Local building departments, through the standard new-construction permitting process; the architectural drawings for the passive system are typically required as part of the permit application itself.
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