Photos courtesy Dryvit Systems Canada
History of energy codes in Canada
Energy codes and guidance documents have been available in Canada for longer than most people know. Now the National Energy Code of Canada for Buildings (NECB) is being adopted in many jurisdictions, it can no longer be relegated to a ‘nice-to-have’ or ‘best practice’ ideal.
According to a presentation delivered by Heather Knudsen of the National Research Council of Canada (NRC) in 2014, the need for energy efficiency guidelines for government buildings was first introduced in 1974. At the initial meeting of the Standing Committee on Energy Conservation in Buildings in November 1976, it was decided prescriptive requirements would be developed based on American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) 90.1, Energy Standard for Buildings Except Low-rise Residential Buildings. The first edition of “Measures for Energy Conservation in New Buildings” was published in 1978, with the second—including a new section for houses—released in 1983. Québec was the only jurisdiction to adopt the measures. In 1990, the Ontario Building Code (OBC) included insulation levels for houses from this 1983 document. (This historical information was taken from “National Energy Code of Canada for Buildings [NECB],” a presentation by Heather Knudsen, P.Eng., at the Manitoba Energy Code for Buildings [MECB] Training Day in September 2014. More is available at www.firecomm.gov.mb.ca/docs/necb_overview_sept2014.pdf.)
In 1997, the first national energy codes were published—one for buildings, and one for houses. The Model National Energy Code for Buildings (MNECB) was referenced in the OBC, and was used in numerous programs, such as Leadership in Energy and Environmental Design (LEED). This code used a prescriptive path for compliance, as well as an ‘engineered’ performance path with computer modelling. Performance requirements varied depending on both the fenestration-to-wall ratio and the energy source.
The next version of NECB was published in 2011, including changes such as a trade-off compliance path, increased performance requirements, and energy-neutral criteria. The improvement in energy requirements across all sectors after introduction of these changes averaged 26.2 per cent.
The newest version of the NECB was published in 2015. Due to provincial code cycles, this version has yet to be adopted across the nation. However, the NECB 2011 has been adopted by several jurisdictions, including:
- Ontario–adopted November 2012, effective January 2014;
- British Columbia–adopted April 2013, effective December 2013;
- Manitoba–adopted December 2013, effective December 2014;
- Nova Scotia–adopted December 2013, effective December 2014; and
- Alberta–adopted February 2015, effective November 2015.
The NECB 2015 pertains to all buildings apart from farm buildings and those covered by part 9—the latter are addressed in the National Building Code of Canada (NBC). Although the material presented here refers primarily to the NECB, energy efficiency concepts relating to exterior walls apply to all buildings.
Continuous insulation and thermal bridging
As code requirements increase, the benefits of using continuous insulation (CI)—such as cost-effective placement, minimal thermal bridging through opaque wall areas, and mitigation of condensation potential—are being recognized. However, the effect of thermal bridging has neither been adequately recognized, nor managed to reflect the actual thermal performance of wall assemblies by accounting for all of the thermal bridging inherent in standard wall construction.
As cited earlier, the most comprehensive document published on this matter to date is the thermal bridging guide produced by Morrison Hershfield and BC Hydro, which contains a comprehensive list of details with effective thermal properties evaluated using 3D modelling. According to the Building Envelope Thermal Bridging Guide:
It has become more and more evident that the thermal performance of the building envelope can be greatly affected by thermal bridging. Thermal bridges are localized areas of high heat flow through walls, roof, and other insulated building envelope components. Thermal bridging is caused by highly conductive elements that penetrate the thermal insulation and/or misaligned planes of thermal insulation. These paths allow heat flow to bypass the insulation layer and reduce the effectiveness of the insulation.
In the November 2016 issue of Construction Canada, an article by John R.S. Edgar entitled, “Improving Continuous Insulation,” examined the impact of thermal bridging on the effective thermal resistance (R-value or RSI) of CI in depth.
“The Morrison Hershfield research has shown this thermal bridging effect can reduce the effective R-value of the ‘clear wall’ by more than 30 per cent,” Edgar wrote. (John R.S. Edgar’s full article, “Improving Continuous Insulation,” was published in the November 2016 issue of Construction Canada. For more, visit the magazine website www.constructioncanada.net/improving-continuous-insulation.)
When CI is truly continuous (i.e. when it involves no thermal bridging), its benefit is fully realized. EIFS, designed and installed as a high-performance cladding solution, is the only continuous insulation and cladding system where thermal bridging is effectively eliminated. Most EIFS are anchored with adhesive, with no thermal bridging—unlike other claddings incorporating clips, anchors, support shelves, or girts.
“The contribution of details that are typically disregarded can result in the underestimation of 20 to 70 per cent of the total heat flow through walls,” according to the Building Envelope Thermal Bridging Guide, but this is not a concern with EIFS.
As a result of the evolving thermal requirements in the NECB, the critical path is the accounting for thermal bridging of assemblies that are not CI. No longer can an insulation riddled with structural penetrations be given its full value in designing for code conformity.
Keeping in mind the effects of thermal bridging, the new reality of the NECB must next be considered.
