Drywall manufacturers have in recent years become concerned with the mold issue in the home building industry. Mold in new residential construction is an issue for builders due to the additional cost of remediation, not to mention visibility with homebuyers. An April 2005 article on www.gypsumtoday.com described a CertainTeed survey that found 55% of 1000 homeowner respondents expressing concerns about mold. For solid materials such as framing members, mold remediation revolves around cleaning and treating. However, for drywall, cleaning may not suffice for drywall, leaving a more expensive effort of removal and replacement.
Mold growth requires moisture and a food source. Therefore, some gypsum board manufacturers have developed products with gypsum cores that will not absorb moisture as easily as typical gypsum board. To reduce the risk of mold growth that paper facings can provide, a number of manufacturers, including U.S. Gypsum (Sheetrock® Brand Humitek®), National Gypsum (Gold Bond Brand XP), and Temple-Inland (Silent-Guard™ TS gypsum shaftliner), chemically treat the paper on both sides of the gypsum board. Some manufacturers eliminate the paper entirely. Georgia Pacific (DensArmor® Plus) replaces the paper with glass mat facings, while U.S. Gypsum (FiberRoc® AquaTough™) uses a gypsum-cellulose combination in their panels that doesn't require paper.
The current standard for mold-resistant characteristics of drywall is ASTM D3273 Standard Test Method for Resistance to Growth of Mold on the Surface of Interior Coatings in an Environmental Chamber. This standard measures the ability of the drywall product to resist mold and mildew growth under certain prescribed moisture conditions, and a number of manufacturers quote the performance of their products when tested to this standard. The numbers achieved by the products mentioned in this discussion achieved between 8 and 10, with 10 being the highest rating and zero being the rating of standard gypsum board. It is important to note, however, that materials are tested for only 30 days, so the standard does not address longevity of the mold resistance treatment.
Mold-resistant does not mean that mold cannot grow. Under the right conditions, mold can grow on almost any surface. These products limit the conditions which are prime for organism growth, reducing the chances for mold.
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Resists mold growth and helps to protect indoor air quality.
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Resists deterioration of drywall exposed to moisture, and reduces maintenance and replacement costs.
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Mold-resistant gypsum board is readily available at many lumber yards. Installation is identical to that of conventional gypsum board. (see Installation)
An August 2005 visit to a Minnesota Home Depot and to Menards, a Home Depot competitor in the upper Midwest, showed 4x8 sheets of ½ inch gypsum board cost $4.98 for conventional and $9.98 for DensArmor® Plus mold resistant sheets at each store. Neither store had the other products listed above. For comparison, water-resistant gypsum board was priced at $6.98. According to recent Atlanta Journal article, Georgia Pacific estimates it costs about $1,000 to upgrade 2300 square foot house with DensArmor® Plus.
No operational cost is associated with this product. However it does reduce the possibility of potentially expensive mold remediation in the event of moisture intrusion.
The International Residential Code (IRC) regulates interior wall coverings in section R702. There are no known issues with code acceptance of these products.
Not Applicable
The dimensions, installation methods, and finishing techniques are exactly the same as traditional gypsum drywall products. Typically, panels are nailed or screwed to the framing and finished with joint compound.
Warranties range from a warranty for no defects at the time of shipment and up to a 3-year warranty on manufacturer's defects, depending upon manufacturer. There is no specific warranty on mold resistance, other than the statement of testing to ASTM D3273.
Mold-resistant gypsum board can help to maintain good indoor air quality - thus providing homeowners with environmental benefits. It also should reduce the probability of costly remediation and litigation - benefiting builders and remodelers, as well as home owners.
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