August 5, 2015
For the fist time in National Building Code history, Part 9: Energy Efficiency sets a minimum benchmark with Section 9.36. To achieve this, there are two optional compliance methods: Prescriptive or Performance.
The prescriptive approach allows the designer to "pick" appropriate envelope solutions from the tables and charts. There is provision made for limited trade-offs (i.e. increasing wall insulation to off-set limited u-value of stain glass custom window) whereas the performance option allows for the minimum efficiency target to be met through showing compliance through modelling (i.e. Hot2000). The performance path further allows the designer to take a more customized approach in meeting the minimum energy efficiency standard.
The minimum efficiency level targeted by 9.36 is approximately equivalent to an EnerGuide™ for New Homes 78 to 80.
National Building Code Section 9.36 also moves away from referencing nominal insulation values and is built around effective R-values. For example, an "extra credit" is available to wall assemblies wherein advanced framing (19.2 or 24"oc) or a layer of continuous exterior insulation is applied. Several industry partner associations have developed thermal assembly calculators to assist designers and professionals with identifying the correct effective R-value. One such tool is the Canadian Wood Councils Thermal Wall Calculator, currently available on the cwc.ca website.
Within the prescriptive path, Heat Recovery Ventilation (HRV) is encouraged as an option; when an HRV or ERV is used the minimum thermal value of the envelope assembly can be slightly reduced or optimized. Additionally, air barrier effectiveness and importance are reinforced by new inspection requirements. Under the performance path there is recognition of actual air leakage test results (blower door) and the significant impact on energy consumption. Along with the envelope enhancements, minimum mechanical efficiencies are also part of the prescriptive requirements; 92% Furnaces, 0.67EF water heaters and 14.5 SEER A/C when applicable.
The minimum energy efficiency level targeted by the National Building Code Section 9.36 is approximately equivalent to an EnerGuide™ for New Homes 78 to 80 (applying HOT2000 10.51 with a range of housing types from attached to detached). It is interesting to note that just a decade ago this was approximately the baseline energy efficiency of R2000 homes in Canada.
If one were to look closely at nearly every heat loss calculation for average new homes in Canada it becomes quickly apparent that 25% to 40% of all heat loss is associated with ventilation and air leakage. There is a noteworthy synergy that will occur in these new homes with enhanced thermal assemblies, HRV and enhanced air tightness performance.
It is advisable that designers of homes under the new National Building Code Section 9.36 should also be reviewing the altered load calculations and subsequent air system or delivery system designs to appropriately account for these new energy efficiency details. Lower heating and cooling loads need right-sized mechanical equipment to minimize the effects of short cycling (uneven temperatures in home and limited equipment operational life). The new CSA F280-2012 will significantly help designers address these new energy efficient residences
By Andrew Oding, Senior Building Science Associate
Originally published in Industry Leaders Speak: Ten Members of the Residential Construction Industry Share Their Insights and Opinions by Judy Penz Sheluk