Proposed Change 1869

Section 9.36. of Division B of the National Building Code of Canada (NBC) 2020 does not account for the energy savings that Code users can achieve through compact architectural design. Smaller attached houses are subject to the same insulation requirements as larger detached houses with extensive floorplans, even though the smaller houses require much less energy. This approach is not only inconsistent with the environment objective of the NBC (which includes limiting the probability of excessive use of energy), but also unnecessarily burdens Code users who build very efficient houses.

The current energy performance path in Section 9.36. requires Code users to demonstrate that the proposed house uses an equal or smaller amount of energy than an equivalent reference house. In accordance with the modeling rules prescribed by Subsection 9.36.5., the reference house comprises a hypothetical house with similar geometry to that of the proposed design, but it is constructed to the minimum prescriptive requirements of Subsections 9.36.2. to 9.36.4. Accordingly, a proposed house’s energy budget reflects the minimum efficiency requirements of Section 9.36., but varies according to the shape and size of the house. As a result, larger houses benefit from larger energy budgets, while smaller houses must meet smaller energy budgets.

The reference house energy budget also varies with building shape; “compact” designs that minimize heat loss area (e.g., row houses, stacked houses, houses with simple shapes or low ceilings) receive more stringent budgets than extensive designs with greater building envelope area per unit of floor area (e.g., ranch-style detached bungalows). While this framework ensures that all buildings complying with Section 9.36. reflect similar levels of energy efficiency (e.g., through use of insulation, glazing, equipment efficiency), it permits the construction of buildings with varying energy use.

This outcome is inconsistent with the environment objective, which seeks to limit energy use. In addition, the existing performance path needlessly burdens Code users who choose more compact and efficient forms by obliging these Code users to construct very well insulated buildings even though the chosen design form inherently uses much less energy than other Code-compliant houses. These requirements may increase housing costs in affordable and entry-level housing markets, which largely comprise compact housing forms (including attached, row and stacked housing units).

Introducing an alternate energy performance compliance path based on energy use intensity (EUI) would allow Code users to demonstrate compliance through compact architectural design. This proposed change enables authorities having jurisdiction to recognize the inherent efficiency of attached, row and stacked housing forms and to credit these houses for energy savings relative to other Code-compliant houses.

The proposed EUI compliance path will also enable Code users to benefit from two inherent advantages of absolute energy targets:

• To better reflect a building’s expected energy consumption.
• To reduce the administrative burden of the code by eliminating the reference house modelling requirements.

For these reasons, other jurisdictions in Canada (e.g., British Columbia, City of Toronto) and abroad have introduced compliance paths based on absolute energy use metrics. Experiences from those jurisdictions also attest to specific challenges associated with EUI compliance for small dwellings and in local climates. Reflecting those lessons, the proposed EUI approach includes requirements that adapt EUI targets to local heating degree-days and to relax EUI limits for smaller houses.

Overall, this EUI compliance path will provide more flexibility for Code users when designing to the tiered energy requirements of Section 9.36. Under this compliance path, Code users can demonstrate energy savings achieved through smaller, simpler and attached compact architectural forms in addition to insulation and mechanical systems efficiency. The introduction of this compliance path could lead to reduced housing costs in affordable and entry-level housing markets.

Finally, this proposed change does not limit the use of existing compliance paths, including the reference and proposed modeling requirements of Subsections 9.36.5. and 9.36.7. Code users who construct houses with high envelope-to-floor area ratios (including houses on narrow lots, prefabricated houses and houses on piles above permafrost) may still use the enhanced energy efficiency measures prescribed elsewhere in Section 9.36. to meet the energy performance requirements.

This proposed change provides an alternate compliance path for meeting the energy-efficiency requirements of Section 9.36., including the energy performance tiers provided in Subsection 9.36.7. This proposed change does not limit or restrict the continued use of the existing compliance paths provided in Section 9.36; Code users who deem the energy use intensity (EUI) compliance path to be more onerous than the existing prescriptive or performance paths may continue to comply via those other paths. Accordingly, this proposed change is not expected to increase the cost or effort required to comply with the Code.

However, many Code users will likely find that complying via the EUI compliance path is simpler and more cost-effective than compliance via the existing prescriptive or performance paths. This outcome is expected because the EUI compliance path recognizes the energy savings inherent in more compact architectural forms. Where Subsection 9.36.7. limits compliance measures to improved building envelopes and enhanced equipment efficiencies, the EUI compliance path offers Code users another tool (i.e., reducing building envelope area) to achieve the same objective.

Research by Natural Resources Canada (NRCan) supports this conclusion. NRCan analyzed the various energy compliance paths using 240 building archetypes representing contemporary residential construction in different locations across Canada. Each of these building archetypes was configured to reflect the minimum prescriptive requirements described in Subsections 9.36.2. to 9.36.4. 

When the compliance of these same building archetypes was assessed via the proposed EUI compliance path, NRCan found that 25% of the building archetypes achieved at least Energy Performance Tier 1 without further modification. An additional 25% of the building archetypes would achieve Energy Performance Tier 1 if equipped with cooling equipment to satisfy the requirement of proposed Article 9.36.8.4.-2025 on design cooling load. The remaining 50% of the building archetypes would not benefit from using the proposed EUI compliance path and would be best served by the existing compliance paths.

Of the 25% of building archetypes that would achieve at least Energy Performance Tier 1, many would be able to achieve higher tier performance under the EUI compliance path without employing additional energy conservation measures. Table 1 provides the percentage of building archetypes that would comply with each of the energy performance tiers when constructed to the minimum requirements of Subsections 9.36.2. to 9.36.4.

Table 1: Building Archetype Compliance via EUI Compliance Path⁽¹⁾ by Compliance Tier and Housing Form

Notes to Table:

(1) When constructed to the prescriptive requirements of NBC Section 9.36.

(2) These archetypes would still comply with the prescriptive requirements of Subsections 9.36.2. to 9.36.4. as well as Energy Performance Tier 1 described in Subsection 9.36.7.

Although all of these building archetypes reflect Code-compliant construction, the EUI compliance path would allow Code users to benefit from demonstrating compliance with higher energy tiers because the architectural form of the building reduces heat loss and overall energy use. The extent to which the EUI compliance path would enable building archetypes to meet the performance levels of higher tiers when constructed to the minimum prescriptive requirements of Subsections 9.36.2. to 9.36.4. depends on the architectural form. Stacked dwelling units that share walls as well as ceilings and/or floors with adjacent units would receive the greatest benefit.

In practice, this result means that the Code users who select compact building designs could comply with a higher energy tier at a lower cost. Highly compact and attached buildings might comply with a higher tier at no additional cost. Additionally, Code users would benefit from considering different architectural forms as an option to reduce the cost of compliance with higher energy performance tiers.

The EUI compliance path would have similar administrative requirements as the existing performance compliance paths. Both approaches rely on modeling and simulation to estimate energy consumption and then compare the results to a benchmark. Some authorities having jurisdiction that use EUI metrics report that administration of this path is somewhat simpler because the reference benchmark is readily computed using heating degree-day and floor area parameters.

Authorities having jurisdiction that adopt this EUI compliance path should note that the local heat loss factor and local energy use factor described in this proposed change reflect current NBC prescriptive requirements (Subsections 9.36.2. to 9.36.4.) and modeling rules (Subsection 9.36.5.). Changes to these requirements and rules in future Code editions would require adjustment to the factors used in the EUI compliance path.

This proposed change would affect designers, building owners, and energy consultants who might choose to use the proposed EUI path to demonstrate compliance.

Code users might find that administration of performance compliance via the EUI path is somewhat easier, as only one energy model would have to be completed instead of two.

In addition, Code users would have the ability to use changes to architectural form as a means of meeting energy conservation requirements.