To what minimum thickness must the underground duct system be encased?

The correct answer, which refers to the minimum thickness required for encasing an underground duct system, is relevant for ensuring durability and protection of the ductwork from external pressures and environmental conditions. A thickness of 4 inches provides a sufficient barrier against potential damage from soil movement, freeze-thaw cycles, and other mechanical impacts.

This standard is often set forth in mechanical codes to ensure that ducts buried underground maintain their integrity over time, preventing leaks and ensuring proper airflow when in use. Duct systems that are not adequately encased may become susceptible to collapse or wear, which can lead to costly repairs and inefficiencies in heating, ventilation, and air conditioning (HVAC) systems.

Understanding this requirement is essential for compliance with local building codes and for the successful installation of HVAC systems that are reliable and efficient in their operation.