New Moisture Barrier Products

In response to the design industry's increased awareness of the risks of mold growth in buildings, manufacturers are responding with new or updated products claiming improved performance at preventing the accumulation of moisture within building assemblies.

Breathable Waterproof Membrane
Henry Company's Blueskin Breather membrane: This self-adhering bituminous membrane is unusual in claiming both legitimate waterproofing capabilities (as opposed to water repellency or dampproofing) and high vapor permeability (37 perms). This company's web site also offers some well-presented background information on the design and performance of the building envelope.

High-Performance Building Wraps
Proctor Group's VaproShield building wrap/underlayment material: This woven high-density polypropylene fabric is water-resistant and has exceptionally high permeability. For example its "WallShield" product lists a vapor transmission rating of 212 perms. (In comparison, traditional 15-lb building felt has a perm rating of approximately 3, and Tyvek, a popular proprietary house wrap has perm rating of 50.

Pactiv Corporation's Raindrop Housewrap: This woven, non-perforated fabric is slightly thicker than 1/8-inch and incorporates closely-spaced vertical drainage channels creating a drainage plane facilitating the removal of water from behind cladding or siding.

Benjamine Obdyke's Home Slicker: This 1/4-inch thick, 3-dimensional nylon matting is another product used to create a drainage plane behind cladding or siding. The company's Home Slicker Plus Typar product provides the same drainage mat material prebonded to a commercial grade housewrap product.

Caution Advised
The topic of moisture movement into and out of the wall assembly is not a simple one. For an introduction to key aspects of this topic, see this site's previous article Air, Moisture, and the Building Envelope. Designers and specifiers are also advised to approach with caution manufacturers' claims for the superior benefits of any particular product. Leakage of the building envelope remains one of the highest risk areas for design liability and thorough research is recommended when designing a specifying such systems.

More Information
_Housewraps and underlayments are discussed on page 206 of the textbook. The role of vapor migration in wall and ceiling assemblies is discussed on pages 604 - 606.