Question

The permeability of materials to water vapor is measured in perms. Materials with higher perm ratings are more breathable than those with lower perm ratings. These ratings vary by material and density. Materials used as vapor barriers have low perm ratings. True or false: a material with a perm rating greater than 1 is considered a "breathable" material?

Answer

True. Materials with perm ratings over 1 are considered breathable. Materials with a perm rating of 0.002, such as rubber sheathing, are not considered breathable.