The Ministry of Municipal Affairs Building and Development Branch recently amended the Building Code Act, 1992, to include the Supplementary Standard SB-12 Energy Efficiency for Housing. The 2012 Code’s Division B, Part 12 introduces new prescriptive and performance compliance packages that represent an energy efficiency improvement in new homes of approximately 15% over the preceding version and will apply to construction for which a permit has been issued after December 31, 2016.
New houses constructed in 2017 will consume 50% less energy than homes built before 2006. The 2015 National Building Code has undergone a major shift in that it now refers to “effective R-Value” as opposed to the “nominal R-value” of the past. Nominal R-value takes into effect the thermal insulation value of only the insulation layer, for example the Walltite sprayed polyurethane foam between the studs whereas “effective R-Value” assigns a value based on the cumulative value of thermal resistance for all materials within the assembly – including both framing members and cavity insulation.
The main reason why the language has changed is thermal bridging. Thermal bridging occurs when a conductive material creates a path for heat flow to bypass the insulation layer, for instance a wood or steel stud. This shortcut significantly reduces the R-value of the insulation layer, lowering the overall performance of the assembly. To minimize this loss of R-value, an insulated sheathing material needs to be placed on the exterior side of the framing members.
Other benefits of the wall assembly with insulation outside of the framing member is that it allows for a warmer cavity with less chance of condensation occurring. Cutting heat loss through improvements to the building envelope (combination of sheathing, framing and insulation) will reduce homeowners’ operating costs and make homes more comfortable. It will shrink the emission of climate-changing greenhouse gases (residential sector accounts for 9% of total emissions in Canada according to NRCan) and move us closer to achieving net zero carbon status for all new homes by 2030.
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