ALEXANDRIA, Va. - Robin Bectel, director of communications for the North American Insulation Manufacturers Association (NAIMA), the trade association which represents manufacturers of fiberglass and rock and slag wool insulation products, said she can point to numerous research projects that provide third-party data showing that fiberglass insulation does not directly contribute to poor indoor air quality (IAQ).

One study she cites is a March 1997 report titled "The Use of an Experimental Room for Monitoring of Airborne Concentrations of Microorganisms, Glass Fibers, and Total Particles," which was published in Indoor Environment Review. H.E. Barney Burroughs, president of IAQ/Building Wellness Consultancy of Alpharetta, Ga., had a keen interest in the study. Burroughs' firm specializes in indoor air quality diagnostics and mitigation.

"I wanted to know the real scientific facts about fibrous glass products so that we could make the correct recommendations to our clients when we observed these products in place," said Burroughs. "Thus, I was pleased to be part of an advisory team that monitored a controlled examination of this issue at the University of Nevada, Las Vegas."

According to Burroughs, the study, which was conducted by Linda Stetzenbach and Mark Buttner of UNLV, proved that fiber shed is "definitely not" a significant issue in buildings having fiberglass component distribution systems.

"When compared with metal ductwork in a side-by-side controlled condition, glass fiber counts are no greater than either metal ductwork or ambient background air," wrote Burroughs.

"This work confirms our own experience in the field and enables us to evaluate distribution systems with greater knowledge and confidence level regardless of their construction material."

In the case of fibrous glass duct liners, it is the belief of NAIMA and Bectel that the installation of these thermal and acoustical liners is one of the keys to a well-designed HVAC system that can deliver occupant comfort and acceptable IAQ.

According to Bectel, duct liners help maintain a consistent air temperature throughout the system, reduce condensation, absorb noise from the system's operation, and conserve energy. "Plus," added Bectel, "fibrous glass duct liners have additional benefits. They are cleanable and have integrated antimicrobial protection."

In a pamphlet produced by NAIMA ("Insulation Facts No. 25"), the association noted that by reducing the heat transfer across the walls of the duct system, fibrous glass duct liner products allow a building's HVAC system to deliver conditioned air at de-sign temperatures.

Because fibrous glass duct liners help reduce condensation outside or inside the air handling system, this reduces the opportunity for microbial growth, according to Bectel.

Saving Energy

In the big picture, the insulating role of fibrous glass air-handling products has become even more important because of the increased emphasis on ventilation as a critical element in IAQ, stressed NAIMA.

Increased ventilation requirements, which mandate a specific cubic foot rate of air per occupant, place more demands on the building's energy source and highlight the benefits of increased efficiency.


The association does admit that there are several places where fibrous glass duct liners should not be used. This list includes:

  • With equipment of any type that does not include automatic maximum temperature controls and where an operating temperature of 250 degrees F may be exceeded.

  • In kitchen or fume exhaust ducts, or ducts conveying solids or corrosive gases.

  • In any application where the liner may come in direct contact with water.

  • Inside fire damper sleeves.

    While there are other applications that are subject to precautions, NAIMA is quick to point out that during the last 40 years, millions of square feet of fibrous glass duct liner have been installed in HVAC systems throughout the United States.

    NAIMA's pamphlet sums it up this way: "When used in modern air-handling systems, fibrous glass duct liners improve the quality of the indoor environment by maintaining a consistent air temperature throughout the system, reducing condensation, and absorbing noise from the system's operation."

    For more information regarding NAIMA, fibrous glass insulation, and fibrous glass duct liner, visit For more information on the UNLV study, contact Barney Burroughs, 225 Mount Rainier Way, Alpharetta, Ga. 30202; call 770-594-1877; 770-552-8757 (fax).

    Publication date: 10/25/2004