Unsealed Vapor Barrier
When installed, 6 mil vapor barriers are not sealed at the seams. They are either laid on the ground or staked with U shaped stakes to help keep them in place. The problem with this is that it creates more holes in a material that is intended to keep the earth's moisture from rising into the crawl space, and instead allowing it. The 6 mil is also flimsy and rips and tears easily as critters and service persons make their way through the crawl space.