Air Barrier Details
Many places in the building envelope such as rim joists, tops and ends of partition walls, openings, services, vent stacks, chimneys, unusual framing details and electrical, plumbing and mechanical penetrations are prone to air leakage (Figure 6) and must be carefully sealed in a durable manner (that is for the life of the building). Durability is important because the air barrier is seldom accessible for maintenance or repairs once the building envelope construction has been completed.
Note : It is important to reiterate that the air barriers described for the following areas of a house must be connected and sealed in order to provide a continuous air barrier system.
Source : Canada Mortgage and Housing Corporation (CMHC)