What is the maximum length allowable for listed air duct material?

The maximum length allowable for listed air duct material is not limited, which reflects the flexibility in design and installation that modern HVAC systems now incorporate. This lack of limitation is conditional on the material itself being properly listed and tested according to safety and performance standards.

When air ducts are made from materials that have been specifically engineered and tested for durability, fire resistance, and efficiency, they can be extended beyond traditional constraints. It is essential to also consider additional factors such as building codes, local regulations, and the specific requirements of the HVAC system being employed.

Even though there might be practical considerations regarding airflow efficiency and pressure loss over long distances, the code does not impose a maximum length restriction on these listed materials. Proper installation practices and adherence to duct sizing principles will dictate the overall effectiveness of the ductwork rather than a fixed maximum length.