What material is commonly used for duct insulation?

Fiberglass is the most commonly used material for duct insulation due to its excellent thermal resistance and sound-dampening properties. It comes in various forms, including batts and rolls, which can be easily installed around ductwork to help maintain the temperature of the air flowing through the ducts. This insulation helps in reducing energy loss, thereby improving system efficiency and reducing heating and cooling costs. The material is not only lightweight, making it easy to handle, but it is also non-combustible and resistant to moisture, which is vital for preventing mold growth in HVAC applications.

In contrast, the other materials listed do not serve a similar purpose in duct insulation. Aluminum, for example, is primarily used for ductwork itself rather than insulation, while cardboard and wood are neither efficient nor suitable materials for insulation in an HVAC context due to their lack of thermal resistance and potential to absorb moisture, leading to deterioration over time.