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REGULAR DUCT MAINTENANCE

Like any other building component, ductwork and duct insulation require proactive care for optimal performance. It is important to schedule periodic duct maintenance to keep ductwork clean and working.

High-efficiency air filters of the correct size and quantity are key components of a well-maintained HVAC system. Ducts should be inspected for the detection and remediation of moisture and contaminants regularly. If dust or debris is present, ducts must be cleaned in accordance with National Air Duct Cleaning Association (NADCA) ACR 2006 Standard, Assessment, Cleaning & Restoration of HVAC Systems. ACR 2006 requires an HVAC system to be under continuous negative pressure when cleaning is performed. Continuous negative pressure is accomplished through the use of a negative air machine. The standard also requires the use of agitation. The three most common methods of agitation are:

• Contact vacuuming
  

  A conventional method of cleaning interior duct surfaces, the hose of a high-powered vacuum cleaner with a high-efficiency-particle-arrestor (HEPA) filter is inserted through access holes cut into ductwork. Particles that become airborne through cleaning and are not collected by the vacuum hose are drawn downstream through the duct and removed from the system, preventing their release into occupied spaces.

• Air sweeping

  When air sweeping is utilized, compressed air is introduced to the duct through a hose capped with a skipper nozzle. The compressed air propels the nozzle through the ductwork, dislodging dirt, dust, and debris. The dislodged particles become airborne and are drawn downstream through the duct and out of the system.

• Power brushing

  A pneumatically or electrically powered rotation bristle brush can be used to loosen dirt, dust, and debris and draw it downstream into a vacuum collector. When dealing with fiberglass ducts or sheet-metal ducts lined with fiberglass insulation, duct-cleaning professionals must take special care to use only specially designed brushes with soft, flexible polymer bristles that remove debris without putting extra stress on surfaces.

CONCLUSION

An HVAC system with ductwork that is properly sealed, well insulated, and well maintained is an excellent defense against poor IAQ in buildings. When more attention is given to efficient duct designs, building and design professionals can produce more sustainable buildings with occupants who are healthier, more comfortable, and, therefore, more productive.

REFERENCE

1. NAIMA. (2002). Insulation facts 34: The facts about mold growth. Alexandria, VA: North American Insulation Manufacturers Association.

For past HPAC Engineering feature articles, visit www.hpac.com.

A product manager with CertainTeed Corp.'s HVAC group, Ken Forsythe previously worked at Alcoa and Ford Motor Co. He received a bachelor's degree in mechanical engineering from the University of Toledo and a master's degree in business administration from the University of Michigan. He can be contacted at ken.d.forsythe@saint-gobain.com.