#2: Performance Characteristics & Considerations In addition to application methods, WRBs may be selected based on performance characteristics best suited to climate or cladding. Considerations include: Drainage Efficiency: In wet areas, additional drainage capabilities may be required. WRBs that offer high drainage performance generally have some type of embossed or textured face, enabling water to drain away more efficiently. (See chapter 4 for more detail on this topic.) Surfactant Resistance: Wood siding may leach a chemical surfactant that can cause water to penetrate some WRBs. Power washing with certain detergents and cleaning solutions containing surfactants may also get behind the cladding, producing the same harmful impact. UV Resistance: Some WRBs offer extended resistance to UV rays from the sun. This is an important consideration for larger projects, such as multifamily construction in which the WRB will be exposed for a longer period before being covered with cladding. Stucco and Masonry: Building code requires two layers of WRB behind these types of claddings. Asphalt Saturated Kraft paper is a good choice for the “sacrificial layer” that is adjacent to the stucco/mortar. Even if some of the stucco sticks to this layer, the second layer will act as a WRB and allow the structure to dry. Vapor Permeability: Weather-resistive barriers can be either vapor permeable or vapor impermeable. In most climate zones, residential buildings typically use a vapor-permeable weather-resistive barrier.
#1: Application Method Mechanically Attached: The most common type of WRB for residential, multifamily, and light commercial structures, available in several types of materials: Asphalt Saturated Kraft Paper – excellent substrate in drier climates and under masonry and stucco Woven polymeric house wraps – plastic tapes woven in 2 directions and coated with a waterproof film. Often these are micro-perforated to allow vapor to escape. These meet code requirements in many areas Spun bonded, Non-woven house wraps – a technically advanced barrier that keeps bulk water out, while allowing the structure to “breathe” Integrated Structural Panel with Weatherization: An all-in-one weatherized panel with an affixed weather barrier. Joints must be taped thoroughly to complete the weatherization envelope. Self-Adhered Weather Barrier: Repels water and reduces air leakage to promote energy efficiency. Typically, this type of WRB self-seals around nails—an added advantage. Fluid Applied: A WRB that is sprayed or rolled on, offering continuous coverage and energy efficiency. Many self-seal around nails.
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