Indoor Environmental Quality

Many factors contribute to a productive learning environment. Acoustics and comfortable temperatures are important factors, discussed elsewhere. A healthy, clean indoor environment is just as important.

One health issue that concerns education professionals is mold growth. The thermal insulating properties of fiber glass protect against damaging moisture. Condensation on the outside of sheet metal ducts can occur when there is no insulating barrier between the conditioned air inside the duct and the ambient air outside it. If air in the bare metal duct is cooled to a temperature below the dewpoint of the ambient air, condensation can form on the sheet metal.

This is one reason the ductwork in Redmond High School; Redmond, Wash., is lined with fiber glass duct liner from Johns Manville. Mechanical engineer Chris Caffee of BCE Engineering, Inc., in Seattle explains, "If the duct runs through warm, humid conditioned space and the air inside the duct is cold enough, condensation forms on the bare duct. This can drip onto ceiling tiles and leave brown water marks and spots. I think this is worse than a leaky pipe because it is so hard to diagnose. If temperatures change, the maintenance crew may not see condensation on the duct and could assume they have a roof leak or some other problem. Condensation is rare, but we always recommend lining ducts to avoid it."

Coated fiber glass insulations offer additional protection. Coatings guard against incursion of dust or dirt into the fiber glass, reducing nutrients microbes need to grow. Many Johns Manville air handling products have a tough acrylic protective coating. This polymer is formulated with an immobilized, EPA-registered protective agent to protect the coating from potential growth of fungus and bacteria. An airstream surface with a quality coating can be cleaned using industry recognized dry methods, should such maintenance be required. When properly installed and maintained, fiber glass ducts and liners will not support microbial growth.

Unfounded concerns about safety of glass fibers were conclusively put to rest by the International Agency for Research on Cancer (IARC), an agency of the World Health Organization. Their review of studies of fiber glass over 15 years show "no evidence of increased risks of lung cancer." Their conclusion is that fiber glass cannot be classified as a human carcinogen.

Find out more about fiber glass from the International Agency for Research on Cancer (IARC)