Weather Resistant Vs. Water Resistant Barriers

Knowing the difference between weather resistance and water resistance is key to choosing the right building wrap for your project.

Codewatcher Drainable wrap TYPAR

Typar’s drainable building wraps meet all current standards for drainage efficiency (ASTM E2273) without sacrificing any of the durability and ease of installation offered by premium building wraps,

The definition is clear: A weather-resistant barrier is generally classified as a material that prevents both water and air infiltration into the building interior, while a water-resistant barrier functions only as a water (liquid and vapor) barrier. Less clear for some building pros is which to pick for a particular job.

The International Code Council Evaluation Service (ICC-ES) evaluates the following five key performance characteristics for building wrap, which provide a valuable starting point for deciding which product best suits a project.

1 Water Resistance

As its most basic function, a building wrap must hold out liquid water. A premium building wrap will be able to pass both “water ponding” tests, which measures a house wrap’s resistance to a pond of 1-inch water over two hours, and a more stringent hydrostatic pressure test where the wrap is subjected to a pressurized column of water for five hours.

“Meeting these testing requirements are paramount, but even more important than how a building wrap performs in a laboratory, is how it performs in the field. While these tests account for water holdout in a controlled environment, it does not take into account real-world scenarios where a building wrap can be torn or ripped on the jobsite or during install,” says Bijan Mansouri, Technical Manager, TYPAR Construction Products. “TYPAR building wraps have been engineered to provide additional tear strength to stand up to the rigors of the jobsite and after the material has been installed.”

2 Air Resistance

According to the Air Barrier Association of America (ABAA), an air barrier system is a system of building assemblies within the building enclosure—designed, installed and integrated in such a manner as to stop the uncontrolled flow of air into and out of the building enclosure. Because an air barrier isolates the indoor environment, it plays a major role in the overall energy efficiency, comfort and indoor air quality of a building.

According to the U.S. Department of Energy, up to 40 percent of the energy used to heat and cool a building is due to uncontrolled air leakage. As such, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 90.1 and the IECC both include air barrier requirements.

For an individual building material to be classified as an air barrier, its air permeance must be equal to or less than 0.02 L/(s-m2) @ 75 Pa when tested in accordance with ASTM E2178. However, this air permeance test only measures the amount of air that migrates through the material itself and not through holes or gaps in the larger assembly. Therefore, it is important to keep in mind that a material’s effectiveness as an air barrier is largely dependent on proper installation and the use of compatible tapes, fasteners and sealants.

“The simplest way to be sure the entire system will work together effectively and meet all code requirements is to specify wrap, tapes and flashing from a single manufacturer,” Mansouri reminds. “Doing so provides added assurance that each component will work together seamlessly, and often the system will be covered by the manufacturer’s warranty. When in doubt, always check the manufacturer’s website for additional guidance.”

3 Durability

The ICC-ES looks at the tear resistance and tensile strength as the best measure of a building wrap’s durability, since it must be able to withstand the handling and application process without compromising its water resistance. UV and low temperature resistance are also important measures of durability because prolonged exposure to the elements can compromise the integrity of the product or cause it to crack.

4 Vapor Permeability

For a product to be considered a building wrap and not a vapor retarder, ICC-ES mandates the permeance rating must be higher than 5 perms. But there are a variety of ways permeability is achieved, and a higher perm rating doesn’t always equal a better building wrap (see “The Sweet Spot for Building Permeability”).

When selecting a building wrap, look for one that hits the “sweet spot” of 10-20 perms to achieve the desired balance of moisture protection and drying capacity. For example, some wraps have mechanical micro-perforations, which may allow the passage of more water vapor, but could also be more vulnerable to bulk water leakage. Generally, it’s better to go with a higher quality, non-perforated or micro-porous product, which allows for sufficient vapor mitigation while providing excellent resistance to bulk water.

5 Drainage

Drainage is widely accepted as one of the most effective measures for reducing moisture damage due to rain penetration. Drainage is a critical component in allowing a building wrap to do its job, particularly in keeping walls dry. Usually this involves the use of furring strips that separate the wrap from the structural sheathing and framing, but new technologies have emerged that are helping to simplify this process.

Building wrap manufacturers have developed new products that integrate drainage gaps into the material itself through creping, embossing, weaving, or filament spacers. These new technologies eliminate the need for furring strips as a capillary break, helping to reduce material costs and streamline installation.

These drainable building wraps meet all current standards for drainage efficiency (ASTM E2273) without sacrificing any of the durability and ease of installation offered by premium building wraps, since they essentially handle and install the same. They are also vapor permeable, helping to address many of the moisture management issues described above.

“To meet the specific drainage needs of various applications, TYPAR has one of the industry’s widest portfolio of drainable wraps,” says Mansouri. “Its newest product, TYPAR Drainable Wrap, combines the performance of traditional TYPAR Building Wrap  with the highly efficient drainage capability. It even comes with a lifetime limited warranty when used as part of the TYPAR Weather Protection System.”

Check into how TYPAR BuildingWrap can help you manage moisture in your homes today visit www.typar.com.

This blog is the second in a four-part series. Click here to read the first one, “The Sweet Spot for Building Material Permeability.”