Question: I am an architect in California; I recently spec’d a 6mil polyethylene vapor barrier for installation in a crawlspace area (as is recommended by UBC and IRC for reduction in ventilation requirements. I have a client who is hyper sensitive to off-gassing. Is there a recommendation for an alternate product which will provide a lessened exposure to that issue?
Answer: VaporBlock 20 Plus is a 20 mil vapor retarder, white on one side, gold on the other. This product blocks 400 times more vapors from gases than any other high performance vapor retarder on the market today. Its cell structure is incredibly tight, so even small molecule gases like methane, radon, VOC’s and carbon dioxide cannot pass through the structure. Water vapor is highly retarded also. This film is stocked in 10’ x 150’ rolls. A special foil backed seaming tape is recommended, 4” x 150’. The absolute king of the crawlspace liners is a product called VaporGuard. This product has a foil lining laminated within its structure, resulting in a perm rate of Zero for water vapor, and incredibly few gases can permeate this liner at all. This one is black, which is not ideal for crawlspaces. Either are considerably superior to any 6 mil product I know. While we are on the subject, most of our business in this industry falls in the 12-20 mil thickness range. We have a significant following from the professionals in the industry, and virtually all of them use engineered films in this range.