What is a common material used for duct insulation?

Fiberglass is a commonly used material for duct insulation due to its excellent thermal resistance properties and sound absorption capabilities. This type of insulation helps maintain the temperature of the air as it travels through the ducts, reducing energy loss and improving overall system efficiency. Fiberglass insulation is lightweight, non-combustible, and resistant to moisture, making it suitable for a variety of HVAC applications.

In contrast to other materials mentioned, foam board can be used for insulation in certain applications, but it is not as frequently applied specifically to ductwork. Air barrier fabric serves a different function primarily related to air sealing rather than thermal insulation. Metal sheeting, while beneficial for duct construction to protect the insulation, does not provide thermal resistance on its own. This distinction highlights why fiberglass remains the preferred choice for insulating ducts in HVAC systems.