Proposed Change 2043

The 2020 edition of the National Building Code of Canada (NBC) introduced energy-efficiency performance tiers in Section 9.36. of Division B, with increasing levels of improvement for buildings and houses, to provide jurisdictions with the option to adopt the most suitable energy performance level or their needs.

Although performance modeling is a common practice, many Code users have requested that prescriptive compliance paths remain in the National Model Codes to simplify achieving energy compliance. However, there are currently only performance requirements and prescriptive trade-off requirements for Energy Performance Tier 2 in Section 9.36. of the NBC.

Failure to develop a Tier 2 prescriptive compliance path would limit Code users to having to choose between following the trade-off compliance path or relying on performance-based requirements that use energy modeling to achieve the Tier 2 energy-efficiency targets.

1.  Building Envelope

A Tier 2 building envelope package was developed for each climate zone for buildings having a conditioned volume greater than 300 m³. The 240 modeled building archetypes were separated by volume, with 219 building archetypes having a conditioned volume greater than 300 m³ and 21 having a conditioned volume of less than or equal to 300 m³.

Two criteria were used to define acceptable Tier 2 building envelope package solutions:

(1)  At least 80% of the building archetypes had to comply with the Tier 2 requirement for percentage heat loss reduction of 5% for volumes greater than 300 m³; and

(2)  On average, the building archetypes had to have a peak heating load less than their reference building.

Numerous combinations of building envelope measures met the criteria noted above. Therefore, additional selection criteria needed to be defined to reduce the number of prescriptive building envelope package solutions to one for each climate zone and building volume.

The two additional criteria were:

(1)  incremental costs had to be minimized to make a solution desirable, and

(2)  component performance of the building envelope had to consistently increase across climate zones.

A fourth criterion was defined to exclude solutions having reduced thermal performance of the building envelope component (e.g., insulation) in colder climate zones. For example, a solution that uses 4.88 RSI for the effective thermal resistance of above-grade walls in climate zone 6 would not be used if the solution for climate zone 5 used 5.69 RSI for above-grade walls.

2.  Airtightness

There is no mandatory airtightness level needed to achieve Tier 2.

3.  Heat/Energy Recovery Ventilators (HRVs/ERVs)

The use of HRVs/ERVs was considered an easy and economical way to save energy; therefore, it was proposed that all Tier 2 houses should be equipped with HRVs/ERVs with minimum 60% sensible recovery efficiency for climate zones 4 and 5, and minimum 70% sensible recovery efficiency for climate zones 6 to 8. Since HRVs/ERVs are required for the Tier 1 building envelope package, they are maintained in the Tier 2 building envelope package.

4.  Service Water Heating Systems

No upgrades above Code-minimum service water heating systems are required to achieve Tier 2.

This proposed change would improve energy performance by following the prescriptive requirements for building envelopes and HVAC systems to achieve Energy Performance Tier 2. Detailed costing data can be found in the supporting document. The total incremental cost to achieve Tier 2 is a very small percentage of the total construction cost.

Buildings with a total volume of conditioned space of less than or equal to 300 m³ have the following energy performance: a percent improvement of ≥ 0%, a percent energy target of ≤ 100% and a percent heat loss reduction of ≥ 0%.

Buildings with a total volume of conditioned space of greater than 300 m³ have the following energy performance: a percent improvement of ≥ 10%, a percent energy target of ≤ 90% and a percent heat loss reduction of ≥ 5%.

This proposed change could be enforced by the infrastructure currently available to enforce the Code. 

This proposed change would facilitate the effective enforcement of high-performance energy solutions in jurisdictions where complying with the performance path presents challenges.

Regulators, builders, designers, engineers, architects, contractors and consultants in provinces and territories where Energy Performance Tier 2 has been adopted for housing and small buildings.