1. What Is Radon-Resistant Construction?
Radon-resistant new construction (RRNC) is a set of techniques incorporated during home building that create barriers to radon entry and provide infrastructure for easy mitigation if needed later. The EPA developed the RRNC guidelines based on decades of research into how radon enters buildings and what prevents it most effectively.
The concept is simple: it is far easier and cheaper to include radon protection during construction than to add it afterward. Installing a gravel layer, membrane, and vent pipe costs $500 to $1,000 during construction. Retrofitting a comparable system in an existing home costs $800 to $2,500.
RRNC features work as a passive system by default, using natural air pressure differences and convection to vent radon from beneath the foundation. If testing after construction shows levels above 4 pCi/L, the system can be activated by simply adding a fan to the existing vent pipe.
2. The Five Key RRNC Components
Gravel Layer (Gas-Permeable Layer)
A 4-inch layer of clean, coarse gravel is placed beneath the concrete slab. This gravel allows soil gases to move freely beneath the foundation, making it possible to draw radon from a wide area using a single suction point. Without this layer, radon can only be pulled from the immediate area around the vent pipe.
Vapor Barrier (Plastic Sheeting)
A heavy-duty polyethylene sheet (minimum 6 mil thickness) is laid over the gravel before the concrete slab is poured. This membrane acts as a gas barrier, preventing radon from passing through the slab. It also reduces moisture migration, which benefits the home in other ways.
Vent Pipe (Radon Stack)
A 3 or 4 inch PVC pipe runs from the gravel layer beneath the slab, up through the home's interior walls, and exits through the roof. This pipe provides a pathway for radon to vent to the outdoors. In passive mode, natural convection draws some radon up and out. If activation is needed, a fan is installed in this pipe.
Sealed Penetrations
All openings through the foundation slab, including plumbing, electrical, and HVAC penetrations, are sealed with appropriate caulk or expanding foam. This reduces the pathways through which radon can bypass the vapor barrier and enter the home directly.
Junction Sealing
The joint where the concrete slab meets the foundation wall (called the cove joint) is sealed. This is one of the most common radon entry points in any home. Sealing it during construction is straightforward; sealing it in a finished home is much more difficult.
3. Passive vs. Active Systems
An RRNC system starts as a passive system. The vent pipe relies on natural convection (warm air rising) to draw some radon from beneath the slab and vent it outdoors. Passive systems can reduce radon levels by 30% to 50%, which may be sufficient in areas with moderate radon potential.
If post-construction testing reveals radon above 4 pCi/L, the passive system is converted to an active system by installing a radon fan in the vent pipe. The fan creates continuous negative pressure beneath the slab, dramatically increasing the system's effectiveness to 90% to 99% radon reduction.
The RRNC Advantage
Because all the infrastructure is already in place, activating an RRNC system is simple and inexpensive. A qualified professional can add a fan, install a manometer, and wire an electrical connection in a few hours for $300 to $800. Compare this to a full retrofit that requires drilling, routing new pipe, and potentially finishing work, at $800 to $2,500.
4. Cost of Including RRNC in New Builds
The total cost of RRNC features during new construction is typically $500 to $1,000. This breaks down roughly as follows:
| Component | Estimated Cost |
|---|---|
| Gravel layer (4 inches) | $100 to $200 (often already included in standard construction) |
| Vapor barrier membrane | $100 to $200 |
| PVC vent pipe and fittings | $150 to $300 |
| Sealing materials | $50 to $100 |
| Labor (incremental) | $100 to $200 |
Many builders already include a gravel base as standard practice, which reduces the incremental RRNC cost. The most significant additions are the vent pipe routing through the home and the vapor barrier installation.
On a $350,000 new home, the RRNC cost represents about 0.2% of the total construction cost. It is one of the least expensive protective features you can include in a new build, and it eliminates a potentially expensive retrofit later.
5. Building Codes and Requirements
RRNC requirements vary significantly by state and locality. The International Residential Code (IRC) includes an appendix (Appendix F) with RRNC provisions, but adoption of this appendix is optional for each jurisdiction.
Several states require RRNC in all new construction, including parts of Colorado, Illinois, Minnesota, and others with well-documented radon problems. Many more states have adopted RRNC requirements in specific high-radon counties or zones.
Georgia does not currently have a statewide RRNC requirement. However, given the radon levels documented in north Georgia counties, including these features voluntarily is a sound investment for anyone building in the northern half of the state.
If you are building a custom home, request RRNC features from your builder regardless of local code requirements. If you are buying new construction from a production builder, ask specifically whether RRNC features are included and get the answer in writing. Explore our building a radon-safe home services, sub-slab depressurization options, and learn about how long radon testing takes for new homes.
6. Questions to Ask Your Builder
Whether you are building custom or buying from a production builder, these questions will help you understand the radon protection in your new home.
Construction Questions
- Is a gravel layer included beneath the slab?
- Will a vapor barrier be installed over the gravel?
- Is a radon vent pipe included in the plans?
- Will foundation penetrations be sealed?
Documentation Questions
- Can I get written confirmation of RRNC features?
- Will I receive photos of installation during construction?
- Does the warranty cover RRNC components?
- Where is the vent pipe access for future fan installation?
