Which air barrier system utilizes gypsum board to achieve its function?

The air barrier system that utilizes gypsum board to achieve its function is indeed the air drywall system. This system utilizes gypsum board as part of the air barrier by sealing joints, seams, and penetrations within the board, creating a continuous barrier against air leakage. Gypsum board can be an effective air barrier when properly installed because it forms a rigid, monolithic surface that limits airflow. Additionally, it can be treated with compounds that can enhance its airtight properties.

On the other hand, liquid-applied membranes and sealed sheathing serve distinct functions and utilize different materials to create air barriers, while exterior insulation is typically not a primary air barrier but can complement air barrier systems. Therefore, the air drywall system stands out as the option specifically employing gypsum board for its air barrier capabilities.