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As discussed throughout this series, adhesives and sealants used outside the building envelope have to adhere to the substrate and seal gaps, and they often need to be as durable as the building itself. Performance is the primary concern, and the chemical constituents often take a back seat. Unlike products used on the interior—where VOCs and other potentially hazardous chemicals can concentrate to create indoor air quality problems for occupants—for exterior products, exposure risk is mostly limited to workers who manufacture and apply the products.
The majority of chemicals used in U.S. building products are not required by law to be tested for health or environmental safety, and companies do not have to list minute amounts of chemicals on material safety data sheets (MSDS), even if they bioaccumulate or are potent toxicants (see Chemistry for Designers: Understanding Hazards in Building Products).
This lack of transparency makes it difficult to assess the full chemical profile of all the various sealants, adhesives, and gaskets on the market today.
The primary standard for emissions from wet-applied adhesives and sealants is South Coast Air Quality Management District Rule-1168, which is pending revision and does not cover tapes or gaskets. This standard establishes VOC limits and restricts the use of chloroform, ethylene dichloride, methylene chloride, perchloroethylene, and trichloroethylene in these products. Some sealants (and the primers required for some) may also fall under SCAQMD Rule-1113 for architectural coatings, if they are thinned enough.
GreenGuard certifies adhesives and sealants to its Children & Schools Standard based on emissions, but neither GreenGuard nor Rule-1168 addresses most chemical constituents found in the following adhesives, sealants and gaskets…but these chemicals can still affect the environment. Here’s a quick overview of the primary technologies used in these products.
Liquid, or wet-applied, adhesives are more likely to expose workers to hazardous emissions than are tapes or gaskets, with latex and solvent-free silicon products generally posing the least risk.
Polyurethanes, which contain isocyanates that may cause lung damage in workers, need to be properly mixed, applied, and cured, but proper ventilation and skin protection should also be used when applying certain acrylics, butyls, polyurethanes, and polysulfides.
PSA tapes are considered “articles” rather than sealants, so they do not require an MSDS and are not covered under SCAQMD Rule-1168 for wet-applied products. A tape’s built-in cover reduces emissions and worker exposure. Though products such as modified bitumen membranes or those that require volatile solvents can still be hazardous to workers, solid acrylic tapes have virtually no VOCs or other emissions and are considered a very low health risk.
Similar to PSA tapes, gaskets are not covered by emissions regulations, but since they contain no volatile solvents and are used in areas unlikely to expose occupants to emissions, these products are unlikely to be a health risk for workers or occupants. Manufacturing and life-cycle impacts are the main environmental concerns with gaskets. Polychloroprene, the primary ingredient in Neoprene, in particular, has been singled out because it is considered a persistent, bioaccumulative toxicant.
The primary objective of exterior adhesives and sealants is keeping water, air, and heat in or out of buildings for the lifespan of the building. There are performance restrictions and limitations within each technology as well as overall cost considerations that inform what products to choose for a specific job.
When possible, select low-emitting tapes over solvent-based wet-applied products—such as solid acrylic tapes over butyl sealants—but there is a place for all these products, and by providing adequate worker training and protection as well as utilizing responsible manufacturing processes, the environmental and health impacts of these products can be minimized.
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