Walls Insulated within and Outboard of the Framing

Figures 21 and 22 show examples of walls insulated within and outboard of the framing space appear in. Some types of semi-rigid insulation come with a spun-bonded polyolefin sheet attached to one surface. This material is vapour permeable but air impermeable, and may serve as an air barrier if the joints between the sheets are taped and if the air barrier system is continuous and sealed at doors, windows and other penetrations. If the air barrier is provided on the interior of the building envelope, the exterior rigid insulation does not need to be sealed unless it is also part of the second plane of protection resisting water ingress.

Figure 21

Figure 22

Electrical and mechanical features such as boxes, pipes and ducts should not be installed in exterior walls. Where this cannot be avoided, the NBC allows slightly reduced insulation levels at these locations provided the plane of insulation is continuous. Air barrier continuity at these penetrations is still important.

Small spaces at intersections in corners and around openings must contain insulation that is not compressed. Walls between dwelling units and garages must be insulated to the same level as exterior walls, whether the garage is heated or not, because garages may be left open for extended periods of time.

Source : Canada Mortgage and Housing Corporation (CMHC)