Existing buildings · Defined
Air barrier
A connected system of materials and joints controlling unintended airflow through the building enclosure.
Why it matters
Air control and vapor diffusion control are different functions. Penetrations and transitions can dominate performance even when the specified field material is suitable. Review continuity across trade boundaries rather than treating each product as an isolated solution.
In practice
A project example
An enclosure test identifies leakage at transitions between windows and adjacent walls.
Technical references
General educational guidance from KOW Building Consultants. Examples are illustrative, not project records. The applicable contract, standard, program, and jurisdiction control the requirements for a specific assignment.