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.
Before specifying efficient heating and cooling equipment, it’s important to do what we can to reduce heating and cooling loads. Insulation is one of the key products to consider here, but because there are so many insulation products on the market, we look for additional benefits. Examples include cellulose insulation with recycled content, mineral wool insulation with no flame retardants, and fiberglass insulation with no formaldehyde binders. Other products in this area are high-performance windows and glazings, products that contribute to building airtight envelopes, products that reduce thermal bridging, and window-retrofit products.
With products in this area under constant development, we are always refining our approach. For example, as we have learned about insulation products with hazardous flame retardants and blowing agents that have high global warming potential, we have removed those products from GreenSpec, pending manufacturing changes. We encourage building professionals to pressure manufacturers for those changes through specification language and purchasing decisions.
Barritech VP, offered by Carlisle, is a vapor-permeable, fluid-applied air barrier membrane. This water-resistant barrier measures at 12 perms of vapor permeability under ASTM E96. It has an air permeance well below the ABAA air tightness threshold for air barrier materials. Barritech VP's VOC content is 52 g/l.
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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