Manufacturers of fluid-applied wall membrane products test and publish many properties for their products. These properties are useful to both specifiers and installers for determining suitability of use for the product.
Among the most important properties of fluid-applied wall membranes is water vapor permeance. This property, tested to ASTM E 96, is the determining characteristic for defining a "non-permeable" versus a "permeable" product. As discussed in a previous post
, ASTM E 96 provides two different test methods.
Method A, "desiccant," and method B "water." Particularly with fluid-applied membranes, the results from these two test methods can be dramatically different. For optimal clarity on hygro-thermal behavior of the membrane, experienced specifiers and installers insist that manufacturers report test results for both ASTM E 96 methods A & B. Find out why