What Is Crawl Space Encapsulation? Crawlspace encapsulations include cleaning out your crawl from all debris and old, wet/sagging insulation. We lay down 10 mil VIPER© virgin resin liner on the soil, preventing outside air and moisture from seeping in. The liner covers your entire crawl space ground surface, around each column, and six inches vertically on the interior crawlspace wall. It is sealed to the walls, using Closed Cell spray foam, to ensure an air and moisture barrier.