INSULATION Glass Fiber Air Transmission Systems: FACTS # The Facts About 34 Mold Growth In this issue, we address the results of recent research into the nature of mold growth which confirms that fiber glass duct liner and duct board will not sustain such growth.

Introduction It is important to note, how- ever, that condensation is not iber glass duct liners and the only source of water in an duct board have been incor- HVAC system. It can occur as a Frectly blamed for contribut- result of water carryover due to ing to mold growth in high faulty coil design, dirty coils, or humidity and high temperature failure of the drain pan to oper- conditions. The fact is that fiber ate properly, or improperly glass is inherently resistant to operating humidifiers. mold growth. Stringent testing in accordance with UL and ASTM standards confirms that fiber Fact #2: glass duct liners and duct board Mold growth is not do not support mold growth.1,2 surface specific In instances where mold growth has been detected on According to the Duke study, the interior surfaces of the wherever water was available, duct system, the cause has microbial growth could be found been an accumulation of dust on any surface of the HVAC sys- and dirt combined with the tem, including metal “flex” duct, presence of water. Under the flat surfaces of metal ducts, these conditions, mold can plastic-lined flex duct, caulks and grow on any interior surface. sealants, conditioning coils, metal sound attenuators, mixing box dampers and internal duct liners. Fact #1: The Duke researchers strongly High humidity may not suggest that removing excess lead to microbial growth water from supply air will mini- mize conditions that can result in According to a recent Duke sustained microbial growth. University study3, mold growth appears to be linked to dew- point conditions rather than the Fact #3: relative humidity. Researchers Fiber glass insulations do found that sustained mold not support mold growth growth could occur when wet conditions were produced Fiber glass insulations are inor- www.naima.org through condensation, as the air ganic and inert and do not sup- is cooled past its dew point. port mold growth. The myth has been that microbes can utilize References Maintenance Procedures the binder and the glass as a food Maintenance procedures include source which will enable them to 1. UL181 Standard for Factory-Made Air Duct and Air Connectors. inspection, detection and remedia- grow; that microbial growth may tion of probable sources of airborne affect the material and eventually 2. ASTM G21 Standard Practices for contaminants and water. diminish the structural integrity Determining Resistance of Synthetic Polymeric Materials to Fungi, and In its publication, Indoor Air of the product. ASTM G22 Standard Practice for Quality, SMACNA (Sheet Metal and Determining Resistance of Plastics Air Conditioning Contractors’ to Bacteria. National Association, Inc.) makes Fact #4 3. Fungal Contamination of HVAC several system design and mainte- Mold growth Surfaces: The Role of the Dew Point nance recommendations to prevent can be prevented in Microbial Amplification, Jerry J. mold growth: Tulis, and Wayne R. Thomann; Occupational and Environmental ■ Promptly detect and permanently The conditions which promote mold growth - the presence of Medicine Division, Duke University repair all areas where water col- Medical Center, Durham, N.C.,1997. lection or leakage has occurred. dust and dirt combined with water - do not normally occur in ■ During the summer, cooling coils properly designed, installed, should be run at a low enough operated and maintained sys- temperature to properly dehu- tems. A regular maintenance midify conditioned air. schedule, along with an efficient ■ Check for, correct, and prevent filtration system, assures protec- further accumulation of stagnant tion of both HVAC system com- water under cooling deck coils of ponents and building occupants. air handling units, through proper inclination and continu- About NAIMA ous drainage of drain pans. Conclusion ■ Water-damaged furnishings, NAIMA is the association for North including carpets, upholstery The conditions which promote American manufacturers of fiber glass, rock and ceiling tiles, should be dis- mold growth do not normally wool, and slag wool insulation products. Its role is to promote energy efficiency and carded rather than disinfected, occur in properly designed, environmental preservation through the to effectively eliminate microbial installed, operated and main- use of fiber glass, rock wool, and slag wool contamination. tained systems. However, in insulation, and to encourage the safe pro- duction and use of these materials. ■ Air handling units should be con- instances where water is allowed For more information, contact: structed so that equipment main- to accumulate in the system, tenance personnel have easy and and/or the system is shut down NAIMA 44 Canal Center Plaza, Suite 310 direct access to both heat for periods of time, conditions can occur which allow mold Alexandria, VA 22314 exchange components and drain Phone: 703-684-0084 pans for checking drainage and growth to occur in the air han- Fax: 703-684-0427 cleaning. Access panels or doors dling duct system, whether it is E-mail: [email protected] Website: http://www.naima.org should be installed where needed. lined or unlined. NAIMA Air Handling ■ Materials with hard surfaces Committee members:

where moisture collection has CertainTeed Corp. promoted microbial growth P.O. Box 860 Valley Forge, PA 19482 (e.g., drain pans, cooling coils) 800-233-8990 should be cleaned and disin- Johns Manville Corp. fected with detergents, chlorine- P.O. Box 5108 Denver, CO 80217 generating slimicides (bleach), 800-654-3103 and/or proprietary biocides. Knauf Fiber Glass Care should be taken to insure One Knauf Drive Shelbyville, IN 46176 that these chemical agents are 800-825-4434 removed before air handling Owens Corning One Owens Corning Parkway units are reactivated. Toledo, OH 43659 800-GET-PINK

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