DRYWALL MOLD RESISTANT - CONTENTS: opinions on using mold-resistant or "mold proof" drywall or gypsum board products as a step in preventing mold growth in buildings - advice. Drywall and gypsum board standards, trade practices, & MSDS Sheets. Is the new "mold resistant drywall" a viable product?
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Guide to mold-resistant drywall: evaluation & opinion:
Using mold-resistant drywall: this article reviews the benefits and limitations of using mold resistant drywall, gypsum board, or Sheetrock(TM)(which is a trademark) as a step in
building mold-resistant construction. We include a list of drywall standards and MSDS information. While mold-resistant drywall may be a good idea for some problem-prone building locations, avoiding mold growth in buildings
requires more than just this product.
We also ask about the probable effectiveness of mold resistant drywall in large part because a careful
reading of the manufacturer's data places very constrained limits on how this new and more expensive drywall is promised to perform.
What are you getting if you buy the new "mold resistant" gypsum panels to use after your mold remediation project?
Both of the major drywall companies are now marketing drywall which is advertised as offering "mold and mildew resistance". I was excited to hear about this because drywall in buildings, when it has gotten wet or been subjected to prolonged high moisture, is a very common place for mold growth.
When a building has been wet or been subject to high indoor humidity, it is common to find problem-mold both on the visible or room-side and often on the hidden or wall-cavity side of drywall (illustrated later in this article).
Photo at left: severe mold contamination on the room-side of drywall in a wet basement. This was not a mold-resistant drywall product. But in this article we question how much better mold resistant drywall can perform under the same conditions that produced this mold problem.
[Click to enlarge any image]
First, Possibly Gouged: at a central New York mold remediation project the contractor told me that his local supplier was charging him four to eight times the cost of "regular" drywall (which he calls "sheetrock" (a trademarked name) or "gyp board" which is slang for gypsum panels.
Second, Promised very little: if the USG submittal sheet for "Sheetrock(R)" Brand Humitek(TM) Gypsum panels is any indicator, the manufacturer has given themselves an impressive escape clause. Quoting from the product limitations on this USG document, using its item numbers:
Photo at left: mold-free drywall in the attic of an older home. This product was also not a mold-resistant drywall material, but has performed perfectly well for several decades.
Avoid exposure to temperatures exceeding 125 deg F (Translation: keep it away from your boiler flue, it's not fire-rated).
Avoid exposure to excessive or continuous moisture before, during and after installation. Eliminate sources of moisture immediately. (Translation: if you put this material in an environment where mold grew on your old drywall, we're not promising that this product will perform any better. That advice is absolutely sound. See MOLD RESISTANT CONSTRUCTION.)
Not suitable for use in high moisture areas such as tub and shower enclosures, gang showers, and other areas subject to direct water exposure. (Translation: you shouldn't have used your old drywall in the bathroom and you shouldn't put this new product near the tub, sink, or shower.)
Non load bearing.
The moisture and mold resistance of this material is cited as "Per ASTM C473, the average water absorption for panels is not greater than 5 percent by weight after two-hour immersion."
Translation: sounds great, doesn't it? Indeed improving the resistance of drywall to moisture uptake should improve its mold resistance, as might painting it.
Really? In our OPINION, what all of this means is simple. In general we only find problem mold growth on drywall that has been subjected to excessive moisture, wetting, or actual building flooding. In other words, ordinary drywall products perform perfectly well in dry environments. Since it would appear that the producers of mold resistant drywall warn that they cannot promise anything about its mold resistance in humid or wet environments, it is difficult to understand why the extra cost for mold resistant drywall would be justified.
And what remains un-defined is "excessive or continuous moisture before, during and after installation". Just as our frustrating conversation with a hardboard siding manufacturer claims rep who told us "don't install it if it's too wet" but who would not give even the most vague hint what "too wet" means, (SIDING, FIBER CEMENT MOISTURE LEVELS ) we are left with a bit of uncertainty about the product and how it can perform.
In other words, if the building is dry you won't see problem mold growth on drywall. If the building is wet, nobody is promising you that the mold-resistant drywall will actually not become moldy.
OPINION: Use mold resistant gypsum panels with hesitation and caution
This product sounds like a great idea but ... considering the limitations stated by the manufacturer, I would want to see a lot more about the make-up, testing, and field-use experience of this material before I'd pay the premium suppliers are getting to provide it to your mold remediation contractor.
Photo at left: severe mold contamination (Memnoniella echinata) in the wall cavity of a drywall covered New York city apartment wall that looked perfectly clean from the wall exterior. (HIDDEN MOLD in CEILINGS / WALLS)
Anyone who has used moldproof drywall and sees what they think is mold growing on this new product is welcome to send a sample to my lab.
If your sample comes from Humitek™ or any other drywall manufacturer who provides mold-resistant drywall, we will process your sample pro-bono.
See DUST / MOLD TEST KIT INSTRUCTIONS for easy and inexpensive mold sampling procedures that work well for identifying mold or other particles found on drywall or on other surfaces.
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Association of the Wall & Ceiling Industry - awci.org "AWCI represents 2,200 companies and organizations in the acoustics systems, ceiling systems, drywall systems, exterior insulation and finishing systems, fireproofing, flooring systems, insulation, and stucco contractors, suppliers and manufacturers and those in allied trades.
Our mission is to provide services and undertake activities that enhance the members' ability to operate a successful business."
Drywall Finishing Council "is a Not For Profit, Mutual Benefit Organization that seeks to represent the issues that are commonly faced by manufacturers of materials used in the finishing of drywall" - see dwfc.org and see this .PDF about the Drywall Finishing Council. The DFC website provides additional documents: "a visual evaluation method for inspecting joint treated gypsum panel surfaces", "Interior Job Condition Specifications For The Application Of Drywall Joint Compounds, Drywall Textures, And Paints/Coatings", and "guidelines for determining the visual performance expectations of a Level 5 finish" drywall systems.
Drywall Grid System Standards:
ASTM C635 Standard Specification for the Manufacture, Performance, and Testing of Metal Suspension Systems for Acoustical Tile and Lay-in Panel Ceilings
ASTM C636 Standard Practice for Installation of Metal Ceiling Suspension Systems for
Acoustical Tile and Lay-in Panels
ASTM C645 Standard Specification for Nonstructural Steel Framing Members
ASTM C754 Standard Specification for Installation of Steel Framing Members to Receive
Screw-Attached Gypsum Panel Products
CISCA Ceiling & Interior Systems Construction Association
DSA PA105 Division of the State Architect (California)
IBC International Building Code
ICC ESR-1289 International Code Council Evaluation Service
NOA 04-0716.03 Dade/Broward County, Florida Product Approval
RR25348 City of Los Angeles Research Report
UBC 25-2 Uniform Building Code Standard (section 25.210, exception 2)
UL Underwriters Laboratories Inc. Fire Resistance Directory
Also see the Armstrong Corporation's article on drywall grid system installation details at armstrong.com/common/c2002/content/files/4279.pdf or contact the company at 877-ARM-STRONG
Gypsum Association, www.gypsum.org - 810 First St. N.E. Suite 510, Washington D.C. 20002, 202-289-4550. A gypsum drywall trade association that includes the following corporations: American Gypsum logo,
CertainTeed Gypsum, Inc.,
CertainTeed Gypsum Canada Inc.,
Federal Gypsum Company,
Lafarge North America,
National Gypsum Co.,
United States Gypsum. (Most of these companies also publish product installation and specifications guides.)
The Gypsum Association association provides quite a few online documents addressing the installation and assessment of gypsum board products, including
Gypsum Board Evaluation Report - ES Report ESR-1338, 12/1/2007, Division 09, Gypsum Board Assemblies, prepared by ICC Evaluation Service, Inc. (icc-es.org) provides an independent evaluation of contemporary drywall or gypsum board products with respect to building code compliance (2006 International Building Code IBC and the 2006 International Residential Code IRC) with respect to interior finish, fire resistance, sound control, structural considerations, thermal barrier, and exterior finish.
Assessing Water Damage to Gypsum Board - (GA-231-06), "general industry conditions for assessing gypsum board that has been exposed to water or elevated levels of moisture. Includes recommendations for drying conditions" -
available for purchase in hard copy form at www.gypsum.org
"Recommended Levels of Gypsum Board Finish", available at www.gypsum.org
Fire Resistance Design Manual GA-600, The 18th edition includes fire-resistance ratings for over 370 gypsum-protected wall, ceiling, roof, column, beam, girder, and truss systems. available for purchase in hard copy form at www.gypsum.org
Recommended Levels of Gypsum Board Finish (GA-214-07), "jointly produced by the four leading associations in the industry, assists specifiers, owners, and contractors to precisely describe the desired finish of individual walls and ceilings to meet specific needs. Avoids non-specific terms like "industry standards" and "workmanlike finish" and the problems they can cause" available for purchase in hard copy form at www.gypsum.org
Repairing Screw or Nail Pops [in drywall or gypsum board] (GA-222-08), "the symptoms, causes, and repair methods for fastener pops in gypsum board surfaces." available for purchase in hard copy form at www.gypsum.org
American Plywood Association, APA, "Portland Manufacturing Company, No. 1, a series of monographs on the history of plywood manufacturing",Plywood Pioneers Association, 31 March, 1967, www.apawood.org
ASHRAE resource on dew point and wall condensation - see the ASHRAE Fundamentals Handbook, available in many libraries. The following three ASHRAE Handbooks are also available at the InspectAPedia bookstore in the third page of our Insulate-Ventilate section:
2005 ASHRAE Handbook : Fundamentals: Inch-Pound Edition (2005 ASHRAE HANDBOOK : Fundamentals : I-P Edition) (Hardcover), Thomas H. Kuehn (Contributor), R. J. Couvillion (Contributor), John W. Coleman (Contributor), Narasipur Suryanarayana (Contributor), Zahid Ayub (Contributor), Robert Parsons (Author), ISBN-10: 1931862702 or ISBN-13: 978-1931862707
2004 ASHRAE Handbook : Heating, Ventilating, and Air-Conditioning: Systems and Equipment : Inch-Pound Edition (2004 ASHRAE Handbook : HVAC Systems and Equipment : I-P Edition) (Hardcover)
by American Society of Heating, ISBN-10: 1931862478 or ISBN-13: 978-1931862479
"2004 ASHRAE Handbook - HVAC Systems and Equipment The 2004 ASHRAE HandbookHVAC Systems and Equipment discusses various common systems and the equipment (components or assemblies) that comprise them, and describes features and differences. This information helps system designers and operators in selecting and using equipment. Major sections include Air-Conditioning and Heating Systems (chapters on system analysis and selection, air distribution, in-room terminal systems, centralized and decentralized systems, heat pumps, panel heating and cooling, cogeneration and engine-driven systems, heat recovery, steam and hydronic systems, district systems, small forced-air systems, infrared radiant heating, and water heating); Air-Handling Equipment (chapters on duct construction, air distribution, fans, coils, evaporative air-coolers, humidifiers, mechanical and desiccant dehumidification, air cleaners, industrial gas cleaning and air pollution control); Heating Equipment (chapters on automatic fuel-burning equipment, boilers, furnaces, in-space heaters, chimneys and flue vent systems, unit heaters, makeup air units, radiators, and solar equipment); General Components (chapters on compressors, condensers, cooling towers, liquid coolers, liquid-chilling systems, centrifugal pumps, motors and drives, pipes and fittings, valves, heat exchangers, and energy recovery equipment); and Unitary Equipment (chapters on air conditioners and heat pumps, room air conditioners and packaged terminal equipment, and a new chapter on mechanical dehumidifiers and heat pipes)."
1996 Ashrae Handbook Heating, Ventilating, and Air-Conditioning Systems and Equipment: Inch-Pound Edition (Hardcover), ISBN-10: 1883413346 or ISBN-13: 978-1883413347 ,
"The 1996 HVAC Systems and Equipment Handbook is the result of ASHRAE's continuing effort to update, expand and reorganize the Handbook Series. Over a third of the book has been revised and augmented with new chapters on hydronic heating and cooling systems design; fans; unit ventilator; unit heaters; and makeup air units. Extensive changes have been added to chapters on panel heating and cooling; cogeneration systems and engine and turbine drives; applied heat pump and heat recovery systems; humidifiers; desiccant dehumidification and pressure drying equipment, air-heating coils; chimney, gas vent, fireplace systems; cooling towers; centrifugal pumps; and air-to-air energy recovery. Separate I-P and SI editions."
The National Institute of Standards and Technology, NIST (nee National Bureau of Standards NBS) is a US government agency - see www.nist.gov
"A Parametric Study of Wall Moisture Contents Using a Revised Variable Indoor Relative Humidity Version of the "Moist" Transient Heat and Moisture Transfer Model [copy on file as/interiors/MOIST_Model_NIST_b95074.pdf ] - ", George Tsongas, Doug Burch, Carolyn Roos, Malcom Cunningham; this paper describes software and the prediction of wall moisture contents. - PDF Document from NIS
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