The most cost-effective moment to address radon is during new home construction — before the slab is poured, before walls are framed, before any remediation is necessary. Building codes are the mechanism through which governments mandate this timing advantage, requiring builders to incorporate radon-resistant features into new residential construction. But because the U.S. building code system is decentralized, RRNC requirements vary dramatically by state and locality.
The International Residential Code and Radon
The International Residential Code (IRC) is a model building code developed by the International Code Council (ICC) and adopted — in some form — by most U.S. states. The IRC includes an appendix (Appendix F: Radon Control Methods) that specifies RRNC requirements for new residential construction. Key IRC Appendix F requirements align with EPA guidance and AARST-ANSI RRNC-2022:
- 4-inch thick gas-permeable layer (3/4″ gravel or equivalent) under the slab
- Polyethylene vapor barrier (minimum 6-mil) between the gas-permeable layer and the slab
- 3-inch or 4-inch PVC vent pipe routed from the sub-slab to above the roofline
- Electrical junction box or outlet in the attic at the anticipated fan location
- Sealing of all major slab penetrations and joints
The critical limitation: IRC appendices are optional. Jurisdictions that adopt the IRC base code are not automatically required to adopt Appendix F. A state can adopt the full IRC with Appendix F (making RRNC mandatory), adopt the IRC without Appendix F (making RRNC voluntary), or adopt a modified version with different RRNC requirements.
Where RRNC Is Mandatory
As of 2026, the following categories of jurisdictions require RRNC:
States with Statewide RRNC Mandates
Several high-radon-risk states have enacted statewide RRNC requirements for new residential construction in Zone 1 (or sometimes all) counties. States with statewide or zone-specific RRNC mandates include portions of Colorado, Iowa, Maryland, Minnesota, Montana, North Dakota, South Dakota, and others. Requirements vary in scope — some mandate full RRNC for all new single-family construction, others require it only in Zone 1 counties or for structures with ground-contact foundations.
Municipalities with Local RRNC Requirements
In states without statewide RRNC mandates, individual counties and municipalities may have adopted RRNC requirements locally. This is common in Zone 1 counties where local officials have responded to elevated community radon levels even in the absence of state mandate. Local adoption varies and is not comprehensively tracked — contact your local building department to confirm requirements for a specific project location.
HUD-Assisted New Construction
Federally assisted new construction projects in EPA Zone 1 counties are subject to HUD radon requirements, which include RRNC features for multifamily projects. This is a federal requirement that operates independently of state or local building codes.
Where RRNC Is Strongly Recommended but Not Required
In the majority of U.S. jurisdictions, RRNC is EPA-recommended but not legally required. Builders in these areas can include RRNC features voluntarily. EPA recommends RRNC for all new construction in Zone 1 counties regardless of local mandate, and recommends it for Zone 2 and Zone 3 as well given the low incremental cost during construction.
Buyers of new construction in non-mandating jurisdictions should ask their builder directly:
- “Does this home include RRNC features per IRC Appendix F or AARST-ANSI RRNC-2022?”
- “Is a passive radon vent pipe included in the construction plans?”
- “Is there a dedicated electrical outlet in the attic for a future radon fan?”
If the builder does not include RRNC, request it as a contract upgrade. The incremental cost is typically $350–$700 — a fraction of post-construction mitigation ($800–$2,500+) and a fraction of the home’s overall purchase price.
The AARST-ANSI RRNC-2022 Standard
Where IRC Appendix F provides the building code mechanism, AARST-ANSI RRNC-2022 provides the comprehensive technical specification. RRNC-2022 is more detailed than the IRC appendix on several points:
- Specifications for alternative gas-permeable materials where gravel is impractical
- Detailed sealing requirements for vapor barrier seams, penetrations, and wall interfaces
- Crawl space-specific RRNC provisions (vented vs. encapsulated designs)
- Quality verification requirements during construction
- Labeling requirements for passive RRNC installations
- Provisions for manufactured home foundations
Projects referencing AARST-ANSI RRNC-2022 in their specifications are held to a higher technical standard than IRC Appendix F alone. Some state radon programs have updated their RRNC requirements to reference RRNC-2022 rather than older EPA guidance documents.
Frequently Asked Questions
Is my new home required to have radon-resistant features?
It depends entirely on your state and local jurisdiction. In states with statewide RRNC mandates, yes — new construction must include IRC Appendix F or AARST-ANSI RRNC features. In most U.S. jurisdictions, RRNC is EPA-recommended but not legally required. Ask your builder directly whether RRNC is included, and request it if it is not — the upgrade cost during construction is minimal.
What is the difference between IRC Appendix F and AARST-ANSI RRNC-2022?
IRC Appendix F is the building code mechanism — the legal framework through which jurisdictions mandate RRNC in new construction. AARST-ANSI RRNC-2022 is the technical standard — the detailed specification for how RRNC components should be installed. Both address the same system components (gas-permeable layer, vapor barrier, vent pipe, electrical outlet), but RRNC-2022 is more comprehensive and is the current authoritative technical reference.
My new home has a passive radon pipe — do I need to do anything?
Test for radon after at least 60 days of occupancy. If results are at or above 4.0 pCi/L, activate the system by adding a fan to the existing pipe — a 1–2 hour installation costing $200–$500. If results are below 4.0 pCi/L, retest every 2 years. The passive pipe is infrastructure for future activation; it does not guarantee low radon levels without a fan.
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