Viper CSX Radiant Crawl Space Vapor Barrier - Full RangeViper CSX is a high performance crawl space vapor barrier designed to prevent moisture migration from the soil into the crawl space. Viper CSX helps guard against mold, mildew, allergens, fungus, radon gas, methane gas, heat loss due to damp insulation, wood rot and overall degradation of the crawl space. Viper CSX is a white, triple ply, extrusion coated, virgin polyethylene membrane laminated to a high density flexible foam core and metalized film.