Flexible air ducts are subject to limitations on what aspect according to the code?

Flexible air ducts are subject to limitations on their length, as defined in the North Carolina Mechanical Code. This limitation is crucial because it directly affects the performance and efficiency of the HVAC system. Longer runs of flexible duct can lead to increased resistance, reduced airflow, and potentially create issues with thermal performance and sound levels.

The code sets specific maximum lengths based on the diameter of the duct and the type of system it is serving. These limitations ensure that the ductwork maintains optimal airflow characteristics, preventing problems like excessive friction loss or the inability to maintain required air changes in a space. Proper adherence to these length restrictions is essential to ensure the mechanical system operates efficiently and effectively.