What is the requirement for external duct insulation that is not spray polyurethane foam?

The requirement for external duct insulation that is not spray polyurethane foam must be factory-insulated. This is because factory insulation provides a consistent level of thermal performance and quality assurance that is often difficult to achieve with field-applied or manual insulation. Factory insulation is typically designed to withstand the conditions ducts are exposed to, including factors like moisture and temperature variations, ensuring a more reliable and durable solution for energy efficiency.

Using factory-insulated ducts can also simplify installation procedures, as these components come pre-assembled, reducing labor time and enhancing overall system performance. This choice aligns well with guidelines aimed at promoting more effective energy conservation practices within mechanical systems.