Radon mitigation in Chicago, IL

The standard mitigation approach for nearly all Chicagoland homes is sub-slab depressurization (SSD). Radon enters from soil gas through the basement slab, sump pits, drain tiles, and any below-grade openings. SSD installs a vent pipe through the slab and uses a continuous-running fan to create negative pressure under the slab — pulling soil gas through the pipe and exhausting above the roofline.

The components: a 3-4" PVC pipe through the slab, sealed at the penetration; pipe routing through the home (often through a closet or utility area); an in-line radon fan; and a U-tube manometer for the homeowner to verify operation. What varies between homes: number of suction points required (most Chicago homes need one; large or compartmentalized basements may need two or three), fan size, and pipe routing. IEMA-licensed mitigators with Chicago experience handle these correctly.

Several Chicago housing patterns require attention during mitigation design:

Chicago bungalows (1900-1940). The 80,000+ Chicago bungalows on the city's north, west, and south sides have a distinctive basement design — full-depth basement, brick foundation walls (often common-brick rather than poured concrete), and a poured-concrete slab. Mitigation works well on bungalows but requires careful attention to brick-wall sealing and the brick-slab joint. An experienced mitigator who has done bungalows specifically gets the configuration right.

Two-flats and three-flats. Chicago's multi-family older stock includes hundreds of thousands of two-flats and three-flats. Mitigation system design has to account for shared basements, multiple HVAC systems, and the legal/practical complications of mitigating a building with multiple unit owners. For owner-occupied two-flats, a single mitigation system typically serves both units.

Greystones (Lincoln Park, Wicker Park, Old Town). Greystone construction includes limestone foundation walls and basements. Standard SSD works on greystones but may require multiple suction points due to compartmentalized basement layouts. Plan for a longer install timeline.

Finished basements. Many Chicago and suburban basements are finished — drywall, drop ceilings, sometimes a complete second living area. Mitigation requires breaking through finished floors at the suction point and routing the vent pipe behind walls or through closets without damaging finishes. Experienced Chicago mitigators design routes that minimize finish damage.

Frost-line and pipe routing. Chicago's 42" frost line affects how radon vent pipe is routed externally if it goes outside before reaching above the roofline. Most Chicago mitigations route the pipe interior through a closet or attic. A licensed mitigator handles this routinely; out-of-state contractors sometimes spec exterior routing that fails in Chicago winters.

New suburban construction with passive RRNC stacks. Many newer Chicago-suburb homes (built since approximately 2010) include a passive radon-resistant new construction stack. Passive stacks reduce radon but don't guarantee levels below 4 pCi/L. Test the home; if results are above 4 pCi/L, an IEMA-licensed mitigator can activate the passive stack with an in-line fan rather than installing a full new system.

Before mitigation: confirmed radon test result.

Short-term test (charcoal canister or alpha-track, 2-7 days, inexpensive): closed-house conditions, basement/lowest-occupied level. Results below 2 pCi/L: low risk. 2-4 pCi/L: borderline. Above 4 pCi/L: EPA action level — mitigate.

Long-term test (alpha-track passive monitor, 90+ days): more accurate annual average. Useful when winter test was high or you want a year-round baseline.

Real-estate transactions: most Chicago-area transactions include radon disclosure or testing under the Illinois Radon Awareness Act. Test results above 4 pCi/L typically trigger mitigation as part of the closing.

After mitigation: post-system testing is essential. Schedule a closed-house test within 24-72 hours of fan activation, then again at 30 days. Properly-installed systems produce results well below 2 pCi/L on both tests.