What type of insulation is typically used in ductwork for HVAC systems?

Fiberglass insulation is the most commonly used type of insulation in ductwork for HVAC systems due to its excellent thermal resistance properties and cost-effectiveness. Fiberglass is made from fine strands of glass and offers a high R-value, which measures insulation's ability to resist heat flow. This is crucial in ductwork to maintain the efficiency of the HVAC system by reducing heat loss or gain as air travels through the ducts.

Additionally, fiberglass insulation is lightweight, easy to handle, and can be installed in various configurations, making it a practical choice for a range of duct sizes and shapes. It is also non-combustible, which is a critical safety feature in any building system.

The other types of insulation mentioned have specific applications but may not offer the same level of performance or practicality for ductwork. For instance, cellulose insulation, while environmentally friendly, is primarily used in wall cavities and attics rather than duct systems. Foam board insulation provides thermal resistance but is more suited for sheathing applications. Mineral wool insulation, known for its fire-resistant properties, is often more expensive and may not provide the necessary flexibility required in duct applications.