Bad Ductwork: Fiberglass and Asbestos

bad ducts

A home ductwork system is the tubes that carry air from your heating and air conditioning system to the individual rooms in a home. Some materials pose no problems, but fiberlgass core ducts and ducts that have asbestos can be promblematic.

Modern ducts usually have a plastic core, with a metal wire helix for shape. This is covered with fiberglass insulation and a vapor barrier cover.

Modern Duct
Modern Duct, photo courtesy of Lowes

Older ducts often have metal cores. Which while functional, are generally not as energy-efficient as modern ducts

However, there are two types of ductwork that are problematic when found in a home.

Fiberglass Core Ducts

In the 1970s ducts made entirely of fiberglass became popular. Without a metal core, these were far less expensive and were considered more energy-efficient at the time. However, over the years, dust, dirt, and grime can build up in the fiberglass, and such ducts can NOT be cleaned.

The bigger potential problem is over time, the fiberglass can break down, which may release fiberglass particles into the air. The actual danger of this is controversial, and there are many articles on the internet claiming this type of ductwork is dangerous, and other articles that argue the claims of danger are overblown.

Fiberglass core duct
Fiberglass core duct

Fiberglass core ductwork looks very similar to older fiberglass over metal core ductwork. Usually, the best way to tell is to push on the duct.

If it is stiff, then it has a metal core. If it gives, then it has a fiberglass core.

Fiberglass Core Duct Work
Fiberglass Core Duct Work

Asbestos Ducts

Asbestos is a naturally occurring fibrous silicate mineral. Asbestos used to be a very common building material because of its natural insulating ability.

It was banned as a building material in the late 1970s because inhaling the mineral fibers can lead to significant health problems. But with so many homes in the Los Angeles area having been built well before the late 1970s, asbestos ductwork is still found in older homes

Asbestos ductwork is usually a metal core with either a white or silver wrap. The wrap often has a cardboard-like look and feel.

asbestos wrapped duct
asbestos wrapped duct

Asbestos, if undisturbed, is usually safe to be around. However, ducts are rarely intact. As the material ages, it becomes easily torn, which disturbs the fibers.

asbestos wrapped duct
asbestos wrapped duct with a tear in the material

Another type of ductwork actually has an asbestos fiber core. Any damage can release asbestos fibers into the home.

asbestos core duct with damage
asbestos core duct with damage

Mixed Ductwork

And yes, sometimes we see more than one kind of ductwork in a home

Fiberglas core (top) with asbestos(bottom)
Fiberglass core (top) with asbestos wrap (bottom)

Do you know what kind of ductwork is in the house you are buying? Book your home inspection today by calling 818-298-3405 or book online here.