Polyethylene strips at end of partition and over wall top plates

It is common to install the ceiling air barrier before the interior partitions are built, because it is easier to make an airtight connection between the wall top plates and unconditioned spaces (such as attics). Alternatively, when the interior partitions are built before the ceiling air barrier is installed, the top and ends of the interior partitions should be covered with strips of polyethylene or polyolefin at least 450 m (18 in.) wide (Figure 12), which are subsequently lapped and sealed to the wall and ceiling air barrier materials.

Figure 12

Polyethylene strips at end of partition and over wall top plates

The strips can be installed between the two top plates to avoid damage during construction (Figure 13).
The air barrier can be lapped under and taped to the strip of polyethylene at the top of the wall. This is sealed to the polyethylene attached to the underside of the roof framing to ensure that the air barrier system is continuous at the junction between the walls and roof. To reduce air leakage through the attic hatch, install a compressible gasket between the opening portion and the frame and latches to keep the hatch closed.

Figure 13

Polyethylene sheet strips in interior wall framing

Source : Canada Mortgage and Housing Corporation (CMHC)