What performance requirement is set for the entire air barrier system?

The correct performance requirement for the entire air barrier system is 0.4 cfm/ft² at 1.56 ft./lbs. or 75 Pa. This value is based on established standards for air leakage control in buildings, which are critical for ensuring proper energy efficiency, indoor air quality, and thermal comfort.

An air barrier system must maintain a specific airflow rate to effectively limit uncontrolled air leakage through the building envelope. A performance requirement of 0.4 cfm/ft² indicates that the air barrier can allow only a minimal amount of air to pass through under specified pressure conditions (1.56 ft./lbs. or 75 Pa). This standard helps in preventing drafts, reducing heating and cooling loads, and minimizing moisture intrusion, thereby contributing to overall building durability and occupant comfort.

The other choices represent airflow rates that are either too high or not in line with the performance criteria defined for efficient air barrier systems. Maintaining the correct level is essential to achieving the intended performance of the air barrier and ensuring the effectiveness of energy conservation measures in a building.