Vapor Barrier Mitigation
Vapor Barrier systems are the least common mitigation style. Homes that need vapor barrier systems have crawlspaces with uncovered dirt and gravel. When we install these systems, we have to completely seal the crawlspace.
In order to seal the crawlspace, we use a combination of vapor barrier sheeting, very strong tape, and plenty of vapor barrier caulking and spray foam to completely seal the space. All of this is installed after rocks and boulders are removed from the crawlspace, the dirt is leveled and smoothed out, and a section of drain tile is buried to ensure that we will have flowing air under the plastic. When the vapor barrier is cut, they are assembled together in the crawlspace with the 6 inch seams completely caulked in between and taped so they will not separate if walked on.
We even consider placing scrap carpet under the plastic sheeting in heavily used walkways to keep the plastic from being broken when its walked on. After the crawlspace is clean, sealed, and usable to us, we take our pipe through the garage, a chase or a closet corner and into the attic. When those are not accessible we can do an exterior install where the fan is installed outside and the exhaust piping is extended above the roofline.
Fan choice on vapor barrier systems is a little more complicated. A GX series fan is usually placed on these systems as they are almost always considered high pressure; however vapor barrier systems are often paired with another branch, pulling from either another crawlspace, or from a sump in basement which would not cross connect with the crawlspace. When vapor barrier systems are installed alongside another system, a knife valve is usually installed in the “looser” or low pressure section of the mitigation system. This ensures that we are able to pull the correct amount of air from each section of the home to mitigate the entire living space.
After mitigation, we run a post test in the same area of the home for the most accurate results. This test ensures that our system is working properly to reduce the radon levels of the home to a minimum. If the post mitigation test does not reach the EPA recommended level of 4 pCi/L, we come back to tweak our system so it runs as effectively as possible.
