Homeowners often ask if a vapor barrier is necessary for optimizing attic insulation and protecting their homes from moisture-related damage. The answer, however, isn’t one-size-fits-all.
A Class II vapor retarder should be placed over a wood subfloor and below the wood flooring when being installed over an unconditioned space. Do not use asphalt- or bitumen-type vapor retarders ...
Most slabs of extended age are not directly underlaid with an effective sub-slab moisture vapor retarder, which is likely the most important component of ASTM F710. ASTM E1745, “Standard ...