The amount of moisture that flows into the building envelope is mainly determined by the amount of air flow across the envelope. Air will either infiltrate or exfiltrate across the envelope depending upon the location of the neutral pressure plane.
The location of the neutral pressure plane varies constantly depending upon the wind effect, the stack effect, and the effects of flues and mechanical equipment. As a result, houses with the same equivalent leakage area may perform differently.
The best way to ensure good overall performance is to minimize the number of air leakage points throughout the building envelope by means of a continuous air barrier.