Moisture brings durability and air quality problems with it, and myriad green products are designed to manage it and keep it out. Given the variety of products available, we look for those that meet key performance standards and that make sense in a whole building assembly—such as vapor-permeable weather-resistive barriers that not only prevent moisture from entering the building envelope but also allow drying when the envelope gets wet.
Just how low the VOC level needs to be for a given product to qualify for inclusion in GreenSpec depends on the product category. For most products, we require certification to California’s health-based emissions standard, CDPH Std Method v1.1 standard (also referred to as California Section 01350), which tests a product’s resultant VOC concentrations in the space after a given period of time. For wet-applied products like paints, caulks, and adhesives, we still also look for VOC content instead of, or in addition to, verified low emissions; this is because emissions testing doesn’t adequately test initial offgassing, and VOC content is currently the only widely available proxy.
W.R. Meadows offers Air-Shield LM, a zero-VOC fluid-applied air barrier. This water-based, single-component membrane is an air, vapor, and liquid moisture barrier. It has a water vapor permeance of 0.03 perms, per ASTM E96. Air-Shield LM can be applied to concrete that has not yet fully dried.
An air barrier is made up of materials and components that are integrated into a system to restrict air flow through the building envelope.
Any material that has an air permeance equal to or less than 0.02L(s•m2) @ 75Pa (equal to the air permeance of drywall) can form part of an air barrier system. However, just having air barrier materials in a building does not create an airtight building. These materials and components must be joined into air barrier assemblies, which are then tied together with additional air barrier components to create a complete air barrier system.
According to the Air Barrier Association of America (ABAA), air barrier materials must be integrated to create assemblies with maximum air leakage no more than 0.20 L(s•m2) @ 75 Pa (per ASTM E2357). Note that the air leakage rate for enclosures is about 10 times greater than the air leakage standard for materials.
Air barriers may or may not also act as a vapor retarder or weather barrier. The air barrier can be on the exterior, the interior of the assembly, or both. Air barrier products listed here are sheet or fluid-applied products designed to limit air infiltration through discontinuities in the building envelope while meeting the ABAA standard.
GreenSpec lists products here that contribute to an air barrier assembly by providing key connections where two materials or systems meeting, or filling holes at common weak points in an air barrier assembly. For more products that contribute to air barriers, see specific sections such as Foamed-in-Place Insulation and Weather Barriers.
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