Radon-resistant new construction (RRNC)
Passive radon systems in new homes
A passive system is built in while the house goes up: a gravel layer, plastic sheeting, a sealed slab and a vent pipe to the roof. A fan can be added later if a test calls for one. Illinois requires it in new homes; Pennsylvania and Colorado leave it to local codes.
What a passive system includes
- Gas-permeable gravel layer
- Radon-resistant construction starts with a 4-inch layer of clean, coarse gravel under the slab.U.S. Environmental Protection Agency, read October 15, 2026
- Plastic sheeting on gravel
- Heavy duty plastic sheeting (6 mil polyethylene) or a vapor retarder goes on top of the gravel.U.S. Environmental Protection Agency, read October 15, 2026
- 3 or 4 inch vent pipe
- A 3 or 4 inch solid PVC Schedule 40 pipe runs from the gravel layer up through the roof.U.S. Environmental Protection Agency, read October 15, 2026
- Attic junction box for fan
- An electrical junction box in the attic lets a fan be added later if testing shows it is needed.U.S. Environmental Protection Agency, read October 15, 2026
- RRNC cheaper than retrofit
- EPA says building in radon-resistant features usually costs the builder less than mitigating after construction; it gives no current dollar figure.U.S. Environmental Protection Agency, read October 15, 2026
- Model code: IRC Appendix F
- EPA points buyers to recognized approaches such as International Residential Code Appendix F, ASTM E 1465-08 and ANSI/AARST RRNC.U.S. Environmental Protection Agency, read October 15, 2026
Illinois: required in new homes since 2013
- Passive system in new homes
- All new residential construction in Illinois must include passive radon resistant construction (Radon Resistant Construction Act, 420 ILCS 52/20).Illinois General Assembly (Illinois Compiled Statutes), read October 15, 2026
- What counts as new residential
- The rule covers original construction of single family homes and buildings with two or fewer apartments, condominiums or town houses.Illinois General Assembly (Illinois Compiled Statutes), read October 15, 2026
- Effective June 1, 2013
- The Radon Resistant Construction Act took effect on June 1, 2013.Illinois General Assembly (Illinois Compiled Statutes), read October 15, 2026
- Who may install and activate
- The builder or its subcontractors may install the passive pipe, but only a licensed radon contractor may add a vent fan or turn it into an active system.Illinois General Assembly (Illinois Compiled Statutes), read October 15, 2026
Pennsylvania: not required statewide
- No statewide new build rule
- Pennsylvania's statewide building code does not require radon-resistant new construction, though a town may adopt it.Pennsylvania Department of Environmental Protection, read October 15, 2026
- Certified mitigator in new builds
- DEP says hiring a certified mitigator while a home is being built is not required, though it is helpful; the law exempts builders' preventive measures.Pennsylvania Department of Environmental Protection, read October 15, 2026
Colorado: local codes decide
- Local RRNC requirements
- CDPHE's radon and real estate page links a list of Colorado jurisdictions that require radon resistant new construction, alongside technical bulletins on inspecting and sealing RRNC systems.Colorado Department of Public Health and Environment, read October 15, 2026
- Standards for new homes
- Colorado's radon professional rules adopt AARST standards for soil gas control and rough-in radon components in new one and two family dwellings and townhouses.Colorado Department of Regulatory Agencies, Office of Radon Professionals (4 CCR 754-1, Code of Colorado Regulations, Secretary of State), read October 15, 2026
Test the new home anyway
- Below 4: retest sometime
- Even with a result under 4 pCi/L, EPA suggests testing again at some point in the future.U.S. Environmental Protection Agency, read October 15, 2026
When a home with a passive pipe tests at 4 pCi/L or more, a fan can be added to the pipe; in Illinois only a licensed radon contractor may add it. Read a result · Illinois licensed mitigators
Sources
- U.S. Environmental Protection Agency, read October 15, 2026.
- U.S. Environmental Protection Agency, read October 15, 2026.
- Illinois General Assembly (Illinois Compiled Statutes), read October 15, 2026.
- Pennsylvania Department of Environmental Protection, read October 15, 2026.
- Colorado Department of Public Health and Environment, read October 15, 2026.
- Colorado Department of Regulatory Agencies, Office of Radon Professionals (4 CCR 754-1, Code of Colorado Regulations, Secretary of State), read October 15, 2026.
- U.S. Environmental Protection Agency, read October 15, 2026.