What part of a residential system would use joist liner?

In a residential HVAC system, joist liner is primarily used in the return air system. The return air system plays a crucial role in circulating air back to the HVAC unit for reconditioning, relying on a network of ductwork that often includes areas above ceilings or in walls. Joist liners are specifically designed to fit in the joist spaces of a building, which allows for more efficient routing of air to be returned to the system.

The use of joist liners in this context helps to minimize air leakage and maintain efficient airflow, ensuring that the system can operate effectively without losing conditioned air. This is particularly important in return air applications, as any loss of air can compromise the overall efficiency of the HVAC system and affect indoor comfort levels. They are not typically utilized in supply air, exhaust air, or fresh air intake systems, where different ducting strategies and materials would be more appropriate to ensure the correct functioning of these components.