These products are environmentally attractive because they need to be replaced less frequently or their maintenance has very low impact, both of which can reduce costs as well as environmental impact.
Robust answers on typical service life of products can be hard to come by, however. In GreenSpec we reserve this criterion for products where the material is clearly more durable than alternatives, such as an exceptionally traffic-resistant polyurethane floor finish. We refer to standardized tests for durability when they are available and appropriate.
We also consider “appropriate durability”: long life is more important in a building envelope than in interior finish materials that will be replaced for aesthetic reasons. Here, reduced maintenance can be particularly important. An example is resilient flooring that doesn’t require regular waxing: an unnecessary use of resources and a health hazard.
Harco Polyurethane Floor Finishes
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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.
Harco, operated by National Paint Industries, offers two-part waterborne polyurethanes for high-traffic residential or commercial applications. According to Harco, the company’s Elite has the hardness and chemical resistance of moisture-cure polyurethane without the toxins. This low-odor polyurethane has a VOC level of 270 g/l with the added hardener. Harco’s Durathane comes with a crosslinker and a lower VOC level (220 g/l) than Elite, but less durability. Like other waterborne polyurethanes, these finishes are non-flammable and dry to a clear finish that won’t yellow. Two-part polyurethanes dry quickly for re-coating but should only be applied by trained professionals. Both of these coatings are available in gloss, semi-gloss, and satin.
Protecting wood floors in commercial or residential settings poses significant challenges. Many of today’s surface coatings are either too toxic (moisture-cure urethane) or lack the durability and require too much maintenance (penetrating oils and wax) to be viable choices for commercial or heavy residential use.
Contemporary waterborne finishes, however, can provide the durability of the toughest oil-based products with fewer negative environmental consequences. These finishes are available in one and two-part systems. One-part polyurethanes are less expensive but may not have the durability of two-part systems. Two-part polyurethanes contain a resin and a hardener or crosslinker. These polys are considered to be the toughest in the industry, but they are expensive and are usually only sold to trained professionals.
Because durability is a key attribute of sustainable finish, proper floor preparation and application are as important as the coating. The failure of urethanes, especially waterbornes, is most often due to application problems: improper wax or dust removal; incompatible sealers, stains, and polys; or insufficient drying time between coats (humidity has a dramatic impact on curing time). Along these lines, GreenSpec has investigated the issue of panelization of athletic flooring.
Depending on the wood, sealers may need to be used to avoid tannin bleed-through, raised grain, and bonding problems. Sealers prepare wood for coating, providing a bond and initial build layer that costs far less than expensive topcoats, but these sealers have to be compatible with the polyurethane being used. Most manufacturers have low-VOC sealers formulated to work with the company’s waterborne finish. Application of any polyurethane should follow manufacturer’s recommendations and those of the National Wood Flooring Association or National Wood Flooring Manufacturers Association.
Note that most polyurethane floor coatings contain isocyanates, which cause asthma and other respiratory problems. To ensure the safety of the workers and occupants, these coatings should be applied by trained professionals with safety equipment and should fully cure before occupants are allowed to enter the building.
Products in GreenSpec use technologies known for their durability, meet California’s South Coast Air Quality Management District’s strict VOC limits, and may be certified by Greenguard or SCS Indoor Advantage and/or derived from natural materials.
LEED Credits
EQc4.2: Low-Emitting Materials—Paints&Coatings
IEQc4.2: Low-Emitting Materials—Paints and Coatings
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