Six industry experts — Michael Coulton, director of new product development, Benjamin Obdyke Inc.; Bob Dahl, business director, Typar Construction Products; Ryan McCoy, product manager, radiant barrier division, Insulation Solutions Inc.; Steve Payne, market development manager, Johns Manville Specialty Products; Jeff Van Sloun, product and program leader, Owens Corning; and Theresa Weston, residential technology team leader, DuPont Tyvek — discuss the state of housewrap:

How are housewraps best categorized in the market — by the material used, price, or both?

Two questions to ask when choosing a housewrap, according to Ryan McCoy, product manager of the radiant barrier division of Insulation Solutions, include: What features do I need for this particular project? And what price am I willing to pay to get those features? (Photograph courtesy of Insulation Solutions)

Coulton: We believe how they will be categorized going forward will be based on whether they provide positive drainage. The fastest-growing segment of the market is in drainable or textured housewraps. There is growing recognition that walls need to drain, as evidenced by the 2006 International Residential Code provision (section 703.1) that states, "The exterior wall envelope shall be designed and constructed in a manner that prevents the accumulation of water within the wall assembly by providing a water-resistant barrier behind the exterior veneer as required by Section 703.2, and a means of draining water that enters the assembly to the exterior." An ordinary housewrap alone may not provide a path for water to positively drain from behind the cladding.

Dahl: Housewraps are mostly differentiated by the technology used to provide vapor permeability ("breathability"), namely perforated products or non-perforated. Perforated products, as their name implies, have small holes poked through their film layer to allow for vapor permeance, but this will adversely impact their bulk water holdout performance, allowing them to basically meet the minimum code requirement. Non-perforated housewraps use a higher level of micro-porosity to achieve breathability, which typically gives them superior bulk water holdout and, in some cases, superior air resistance.

Coulton

McCoy: Guiding questions when choosing a housewrap should include: What features do I need for this particular project (i.e., tear resistance, ultraviolet [UV] resistance, extra energy efficiency, etc.)? What price am I willing to pay to get those features? The best housewraps include a combination of desirable features at an affordable price.

Dahl

Payne: Housewraps are categorized using the terms "high end" and "low end," which refer to quality and price. High-end housewraps are those made of nonwoven, nonperforated, engineered polymeric materials. Most of the market growth is occurring in this category, driven by local, regional, and national building code changes, more of which are requiring these types of housewraps for their superior resistance to vapor, water, and air infiltration. The next quality level down is perforated wovens and perforated films. As the names suggest, perforated wovens are materials with tiny perforations that allow water vapor to escape. Perforated films are cross-laminated films with perforations. With these perforations, however, comes decreased performance with regard to water and air infiltration. At the bottom of the quality/price ladder is Grade B building paper, a.k.a. asphalt saturated kraft (ASK) paper. Grade B building paper is similar to roofing paper, but it is lighter and designed to be a "weather-resistive barrier," specifically intended for use in exterior wall assemblies. It functions, but its level of performance falls significantly below nonwoven, nonperforated, polymeric products — or even perforated products.

Van Sloun: One way the industry should categorize housewraps is by strength. Materials such as woven polyolefin fabric, which has a high trapezoidal tearing strength of 37 pounds, are more resilient to the elements. Non-woven materials often have a much weaker trapezoidal tearing strength and can tear and rip as a result of high wind, weather, and other factors, thus compromising the moisture resistance within the home.