Choosing the Right Crawl Space Vapor Barrier for Radon Mitigation Systems
When it comes to radon mitigation, especially in crawl spaces, the quality of your vapor barrier can make all the difference. Contractors know the importance of installing complete mitigation systems that include ventilation, fans, and piping—but the vapor barrier is often the unsung hero. It’s not just about keeping out moisture; it’s about creating a reliable line of defense against soil gas intrusion.
According to the U.S. Environmental Protection Agency (EPA), a vapor barrier used in radon-resistant construction should function as a “soil gas retarder” to reduce radon infiltration through the foundation. The EPA recommends using a vapor barrier with a minimum thickness of 6 mils in radon-resistant new construction. EPA Reference
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What Defines a Radon-Ready Crawl Space Vapor Barrier?
While homeowners may be focused on mold prevention and energy efficiency, professionals understand that not all vapor barriers are equipped to address radon. A standard barrier may offer decent moisture protection, but if radon is the concern, specific technical benchmarks should be met:
- Radon Diffusion Coefficient: A critical value that identifies whether the material has been independently tested for radon gas resistance.
- ASTM E1745 Compliance: This standard governs plastic vapor retarders used under slabs and over soil. Barriers should meet Class A, B, or C standards for durability and puncture resistance.
- ASTM E96 Tested: While this standard measures water vapor transmission, materials with low permeance tend to perform better in soil gas resistance overall—especially in damp crawl spaces.
Related Article: How Long Does a Crawl Space Vapor Barrier Last
Crawl Space Vapor Barriers for the Best Radon Mitigation System
The best way to mitigate radon is to install an Active Soil Depressurization (ASD) system. A well-designed ASD system uses soil gas collectors, fans and piping in partnership with a vapor barrier to create a low-pressure environment that collects radon underneath the house. This system is installed in new homes and can be easily installed in older homes.
Expert Insight
“The most important feature of a vapor barrier for radon is that it has a Radon Diffusion Coefficient, which means it has been specifically tested for use with radon or other gases,” says Jason Treiger, a 28-year construction veteran and product expert at Americover.
Americover’s vapor barriers are BABA-compliant, manufactured in the USA, and engineered for performance in high-risk environments like crawl spaces. These multi-layer, polyolefin-based membranes are designed to resist tears, punctures, and—most importantly—radon intrusion.
Related Article: What is ASTM E96, and Which Vapor Retarder Does it Require?
Below are some recommendations by Americover experts on the best vapor barriers for radon mitigation systems. While most of the vapor barriers listed here offer strong protection against soil gases and moisture, VaporBlock® Plus is the only product that provides certified performance against radon diffusion. If your client is concerned about radon exposure, this is the solution you can trust.
Pro Crawl Anti-Mold Vapor Barrier with MPT™:
ASTM E1745 Class A, B, and C compliant with a permeance of just 0.022 perms. While not radon-tested, it’s highly effective for most soil gases and moisture.
VaporBlock® Plus Vapor Barrier:
Our top recommendation for radon mitigation. Tested specifically for radon diffusion and meets ASTM E1745 Class A, B, and C standards.
Vapor Barrier Retarder:An ultra-durable polyolefin membrane offering maximum puncture resistance and proven radon-blocking performance.
String Reinforced Plastic Sheeting:
Durable, layered protection. While not radon-tested, these barriers still perform well as part of a complete system.
Budget-friendly barrier with strong puncture resistance. Suitable for moisture control and general soil gas redirection.
Enkavent 2-2-2 Foundation Ventilation Mat
Enkavent is a three-dimensional foundation ventilation mat made of durable nylon filaments that create a passive air gap beneath vapor barriers. In radon mitigation systems, especially those used in crawl spaces and underslab environments, Enkavent enhances the performance of the system by allowing soil gases, including radon, to flow freely beneath the barrier. This added airspace improves the effectiveness of venting systems by directing radon toward collection and exhaust points instead of allowing it to accumulate under the structure. When paired with a high-performance vapor barrier, Enkavent helps contractors deliver more efficient and reliable radon mitigation solutions. Shop Now
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