An air duct is used in heating, ventilation and air conditioning systems. They are the pathways for heated or cooled air to travel throughout a building, be it a home, office, factory or warehouse.
Air ducts are used to distribute air throughout a building, or to exhaust air outside of a building.
The most common types of air duct are: sheet metal, fiberglass lined, fiberboard, and flex-line air ducts. Here’s a little bit about the different types..
The most common type of rigid air duct is made with a galvanized steel or aluminum. Sheet metal air ducts the most common because they are the most durable type of air duct construction. They can be round, rectangular, or in the form of a spiral oval, and because their non-porous surface, are the least likely to have mold or biological growth.
Some sheet metal air ducts get lined with an external or internal fiberglass duct liner. Fiberglass lining is used to insulate air ducts from heat loss or to avoid condensation in cases where the supply air is very cold, or there is a high ambient humidity in the plenum. Fiberglass lining is also used to provides sound attenuation.
Flexible air ducts are made with a spring steel wire helix, encapsulated in polymer plastic. Flexible air ducts are inexpensive, lightweight, and easy to install. The lengths of the flexible air ducts be kept as short as possible as the length of flexible, and numbers bends within the flexible affects system performance.
Fiberboard air ducts are constructed with boards of compressed resin bonded inorganic glass fibers. They have a foil face on the outside that serves as the air barrier and water vapor retarder. The interior of fiberboard air duct is sealed to prevent fiberglass fibers from entering the air stream. Fiberboard air duct also provide acoustical and thermal benefits, and are typically the most inexpensive air duct systems to install.