Radon barrier, often called vapor barrier, is a plastic sheet that is installed in a crawl space or under a concrete slab to make it harder for radon to penetrate the thermal envelope of a home. All barriers have some sort of permeability and due to the stack effect the home is often trying to pull air in from beneath the barrier, which is why blocking the radon alone is not an option. These barriers work in conjunction with an active soil depressurization system. You can read more on the difference between encapsulation (blocking) and depressurizing in this article.
Radon barriers have many different specifications. Things like: millimeter or “mil” thickness, ASTM classification, tear resistance and other strength and durability markers. In most radon standards there is no mil thickness requirement–however amongst the general public–mil thickness is the most sought after purchasing qualifier (aside from price). Nearly every customer I speak to knows what mil thickness they want, but they hardly ever know why. I liken it to buying a car based on how many cylinders the engine has: it’s a dated way to make a buying decision.
ASTM Class is a better way to choose a radon barrier. Classifications A, B, and C have to do with the tensile and puncture strength of the barriers. A class is stronger than C class. All the barriers sold by PDS are CLASS A. If you compare the technical data sheets (TDS) of a barrier sold at PDS to the same mil thickness barrier sold by a big box store, you’ll see that the PDS barrier wins in nearly all categories.
Oftentimes a Class A 6 mil barrier will be significantly stronger and more resistant to puncture than a Class C 10 mil barrier. This is why it’s important to check the standard of the barrier your contractor is supplying. When I speak with DIYers, I most often see them choosing a barrier that is way too thick for their needs, which wastes their money and resources all while making the installation more difficult. 20 mil barriers, for example, are used most often to cover landfills or brownfield sites, this is overkill for your home and a waste of resources.
Other considerations to take when selecting a radon or vapor barrier:
- Will the homeowner or tradesman be walking on this barrier (or will it be sealed on concrete)? If so, CLASS A is a must. Woven is usually best.
- Will it be mechanically fastened to the walls? (for crawlspace retrofits, it should). If not, then anything over 6 mil will peel off over time as sealant alone is not enough to hold it.
- Will there be furnaces or other appliances placed on top? Then choose a 10 mil class A
- Will there be standing water in this area? You may need a dranjer fitting, see here
- Is this going in accordance with our soil gas collector mat under a slab? Then you probably don’t need one! CHA-CHING!
Please contact us or your certified professional for more help choosing a barrier. You can also use this handy package we created for most homes here.
Thank you for reading
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