Duct board is a type of rigid insulation material commonly used in heating, ventilation, and air conditioning (HVAC) systems. It's designed to be used in the construction of ducts that carry air for heating and cooling. The board is typically made of fiberglass or other types of insulating materials and is often used for both thermal and acoustic insulation. Duct board is lightweight, durable, and helps in reducing energy loss by maintaining the temperature of air flowing through HVAC systems. It's often used in both residential and commercial applications to improve the efficiency of air distribution.