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.
Certainteed AirRenew Gypsum Board
An additive in AirRenew wallboard reacts with formaldehyde and other aldehydes in indoor air, trapping it in the gypsum core in a form that makes the formaldehyde chemically harmless after absorption, according to CertainTeed. The company won't reveal its formula, but it uses a chemical formaldehyde scavenger, similar to those sometimes added to wood products to decrease formaldehyde offgassing. AirRenew is visually and structurally identical to standard paper-faced wallboard, and is installed the same way. Because the chemical reaction depends on vapor flow through the walls, only breathable wallpapers and latex paints should be applied to AirRenew. Based on a typical formaldehyde concentration in indoor air of 4–18 parts per billion, the manufacturer thinks the gypsum core could continue to absorb aldehydes for 75 years. AirRenew incorporates the company’s “M2Tech” treatment, which includes an undisclosed antimicrobial biocide for mold prevention. GreenSpec frowns upon the use of biocides in broad-based applications like these.
Gypsum board, or drywall, is typically made with 100% recycled, unbleached paper facings that are bonded without adhesives onto a gypsum core.
Mined gypsum is still widely used in gypsum board production, but recycled and synthetic gypsum increasingly contribute to production. Post-consumer recycled gypsum is mainly comprised of scraps from construction. Pre-consumer recycled content includes synthetic, or flue-gas desulfurization (FGD) gypsum, a coal-combustion byproduct obtained from stack scrubbers that remove sulfur from coal-fired power plant emissions.
Synthetic gypsum may replace up to 100% of the natural gypsum in drywall. The amount of recycled content in drywall varies not only by manufacturer, but also by product and by manufacturing location, so if you’re looking for recycled content, be sure to ask manufacturers for specific figures.
In synthetic gypsum, and to some degree in virgin gypsum as well, toxic hazards and heavy metals are concerns at the manufacturing and end-of-life stages of the product. Although heavy metals don’t concentrate in synthetic gypsum the same way they do in fly ash, they are still present in small amounts, and those amounts may increase as power-plant emissions standards tighten. (For more discussion of these issues, see "Measuring Drywall Against Environmental Standards” in EBN.)
While indoor environmental quality concerns haven’t yet emerged with gypsum board made in the U.S., watch out for leaching concerns in landfills, and when recycling gypsum board as an agricultural amendment.
Paper facings provide an ideal medium for mold growth in conditions of high humidity, or if wallboard gets wet due to flooding or leaking water. To combat this, manufacturers include biocide treatments in some product lines, and offer other product lines with integral cellulose or fiberglass fibers instead of paper facing.
GreenSpec is concerned about introducing biocides into building products, and considers them ineffective in fighting mold. GreenSpec recommends non-paper-faced wallboard in applications where moisture may be a concern, and includes specific listings for those products.
GreenSpec also lists standard drywall products for North American manufacturers that typically offer recycled content, Greenguard Children & Schools certifications, and certification to UL Environment ISR 100.
Drywall is energy-intensive to produce, and so avoiding waste is one of the easiest steps to reduce your environmental impact in this area. For example, consider 54"-wide gypsum board for more efficient wall coverage in rooms with 9' ceilings.
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