Aside from closing crawl space vents and doors, a vapor barrier is another way to make sure nothing can get into your crawl space. Specifically, this addresses dirt crawl spaces and the unique ways in which it can enforce crawl space moisture. With a crawl space vapor barrier, you no longer have to worry about crawl space moisture that comes up from a dirt crawl space, because the vapor barrier traps that water vapor outside the crawl space itself.
There are many ways to install a vapor barrier. For example, all these unvented crawl space options require a vapor barrier that covers the crawl space in some way, and North Carolina even requires the barrier be at least 6-mil. However, 6-mil is a pitiful crawl space vapor barrier that may actually impact the health and wellness of the crawl space. That’s why JES only opts for the 20-mil CrawlSeal vapor barrier that keeps conditioned air in and water vapor out.