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Why Naperville Has a Serious Radon Problem

Naperville sits in DuPage and Will Counties in the western Chicago suburbs — and it has one of the highest radon rates in the metro area. Over 50% of homes tested in Naperville have returned results above the EPA action level of 4 pCi/L. DuPage County’s average indoor radon reading is approximately 4.3 pCi/L, which already exceeds the federal action threshold.

The geology beneath Naperville’s subdivisions is the primary driver. Glacial till deposits and dolomite limestone bedrock common throughout DuPage County create natural pathways for radon gas to migrate upward through the soil and into home foundations. Naperville’s housing stock — predominantly single-family homes with full basements — is especially susceptible because basements create the pressure differential that draws radon indoors.

Radon is an invisible, odorless radioactive gas produced by the natural decay of uranium in soil and rock. It enters homes through foundation cracks, pipe penetrations, sump pits, and construction joints. The EPA estimates that radon causes approximately 21,000 lung cancer deaths annually in the United States — making it the leading cause of lung cancer among non-smokers.

Because radon cannot be detected by human senses, the only way to know your Naperville home’s radon level is to test.

What Illinois Law Requires for Radon

Illinois has some of the strongest radon disclosure requirements in the country. Under the Illinois Radon Awareness Act (420 ILCS 46), every home seller must provide buyers with the IEMA radon information pamphlet and a signed Disclosure of Information on Radon Hazards form before the buyer is contractually bound.

Sellers must also disclose any known radon test results and provide copies of test records. While the law does not technically mandate testing, the practical effect is that virtually every informed buyer in Naperville requests a professional radon test as part of their home inspection. With over half of local tests coming back elevated, radon mitigation is one of the most common outcomes of a real estate transaction in this market.

As of January 2024, the expanded Illinois Tenant Radon Protection Act also requires radon disclosure for most residential leases. Landlords must disclose any known elevated radon levels and allow tenants to test at their own expense. If radon is found above 4.0 pCi/L, landlords who don’t mitigate may face lease termination.

All radon testing and mitigation professionals in Illinois must be licensed through the Illinois Emergency Management Agency (IEMA). The Radon Industry Licensing Act (420 ILCS 44) imposes penalties of up to $5,000 per offense for unlicensed work. Always verify your contractor’s IEMA license before hiring.

How Radon Mitigation Works in Naperville Homes

The most common mitigation method for Naperville homes is sub-slab depressurization (SSD). A licensed contractor drills a small hole through your basement slab, installs a PVC pipe from below the slab to above the roofline, and attaches a continuously running fan. This creates negative pressure beneath your foundation, pulling radon gas out before it enters your living space and venting it harmlessly above the roof.

Most installations are completed in a single day — typically 4 to 8 hours. The system runs continuously and quietly, drawing about as much electricity as a standard light bulb ($50–$150 per year). A follow-up radon test 24–48 hours after installation confirms that levels have dropped below the EPA action level. Properly installed systems reduce indoor radon by up to 99%.

For more details on how these systems work, see our complete radon mitigation guide.

Radon Mitigation Cost in Naperville, IL

The typical cost for a standard sub-slab depressurization system in the Naperville area ranges from $1,100 to $2,000. The Chicago metro average for a straightforward installation is approximately $1,300–$1,500.

Factors that affect pricing include home size, foundation type, number of suction points needed, pipe routing complexity, and whether the home has multiple foundation types. Complex homes may cost $2,000–$2,500 or more.

For a detailed breakdown, see our radon mitigation cost guide.

Get a Free Radon Quote in Naperville

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Verify Your Radon Levels

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Frequently Asked Questions

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RadonSafetyGuide.com is an independent resource that connects homeowners with certified radon professionals. We are not a radon mitigation company. All services are performed by independent, licensed contractors. Illinois radon contractors must hold an active IEMA license.