Cantilever or Exposed Floors
This section discusses:
Performance of the insulation and AVB in floors exposed to exterior elements
In general, cantilever floors to accommodate such items as fireplaces, china cabinets or bay windows, and exposed floors inherent in rooms over unheated garages, represent a small percentage of the overall building envelope surface area. Focusing efforts solely on increasing levels of insulation in this small portion of surface area will have minimum impact on overall heating costs. While they need to be well insulated, our focus needs to be on constructing an "air tight" air barrier and building exposed floors that improve the comfort of living on the floor above.
Why you should be concerned over the amount of insulation and the AVB within exposed floors
The Manitoba Building Code requires R-32 insulation to be installed in all floors exposed to the exterior elements. It also requires that a structurally supported air barrier be incorporated as part of the floor design detail. While it is fairly easy to accommodate a batt of R-32 fiberglass insulation within a 2 x 10 floor joist, the proper installation of the air and vapour barrier (AVB) poses significant challenges.
The proper detailing and installation of the AVB in the transition between floors is critical to proper long-term performance and comfort of the floor.
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