In terms of performance, what is the ideal outcome of a well-functioning air barrier system?

A well-functioning air barrier system is designed to control the movement of air in and out of the building envelope. The ideal outcome of such a system is to achieve a uniform temperature and humidity distribution throughout the building. This ensures comfort for occupants and efficient operation of HVAC systems, as it minimizes drafts and prevents condensation, which can lead to moisture problems and mold growth.

When air can move freely through walls, as suggested in one of the other options, it can lead to unintended air leaks, resulting in energy loss and uneven indoor climates. Minimal thermal insulation and varied temperatures across different rooms can compromise the effectiveness of heating and cooling systems, negatively impacting energy efficiency and comfort. Thus, a uniform distribution of temperature and humidity signifies that the air barrier is successfully performing its role in maintaining the desired indoor environmental conditions.