What must be installed over exposed duct liner edges that face opposite the airflow direction?

In the context of addressing the installation of exposed duct liner edges that face opposite the airflow direction, using sleeves is the correct choice. Sleeves serve as protective elements that cover and secure the duct liner edges. When duct liners are installed, the edges that are exposed can be vulnerable to damage and degradation, particularly when air is flowing against them.

The primary purpose of sleeves is to ensure that these exposed edges are adequately protected from the airflow, which can help prevent potential disturbances in the airflow pattern and maintain the integrity of the duct system. By using sleeves, you effectively create a barrier that minimizes the risk of fraying or degradation of the duct liner material, contributing to the longevity and efficacy of the HVAC system.

Additionally, sleeves can help in maintaining aesthetic appearances and promoting better overall duct performance by preventing contaminants from entering or accumulating in the liner edges. This attention to detail is crucial for the efficient operation of heating, ventilation, and air conditioning systems in compliance with the North Carolina Mechanical Code.