Wide sheets of standard ___________ may be used as a vapor barrier within a crawl space.

• A. 6 mil polyethylene film
• B. Kraft Paper
• C. Plexiglass
• D. Aluminum foil

Answer: (A)

Moisture control under a building relies on a vapor barrier that blocks soil moisture from seeping into the crawl space. Wide sheets of standard six-mil polyethylene film fit this role well because plastic film is inexpensive, flexible, and nearly impermeable to water vapor, which makes it effective for covering large ground areas with fewer seams. Kraft paper is porous and can absorb moisture, so it isn’t suitable as a vapor barrier. Plexiglass is rigid and cannot form a continuous barrier on the ground. Aluminum foil is not typically used by itself as a crawl-space vapor barrier and can be prone to tearing or shifting. So, six-mil polyethylene film is the appropriate choice.