The National Research Council (NRC) presented updated modelling results for proposed Tier 3 and Tier 4 prescriptive packages under the energy efficiency provisions. Tier 3 modelling is based on NBC Article 9.36.6 and assumes an airtightness level of 2.5 ACH for modelling purposes. While blower door testing is included in the proposed prescriptive package, CHBA noted that, although it recognizes the broader value of blower door testing, it strongly disagrees with mandating testing at Tier 3 where no compliance threshold applies. CHBA highlighted both the added cost burden to builders and the limited value of requiring blower door tests when results are not used for compliance or meaningfully reported. Under the current proposal, test results would be reported only, with no minimum performance requirement.

For Tier 3 buildings under 300 m², the proposed package increases gas furnace efficiency to 98% AFUE, with a minimum domestic hot water efficiency of 0.8. For oil furnaces, the proposed AFUE is 87%, with the same hot water efficiency requirement. For buildings 300 m² and greater, wall and ceiling insulation levels increase by climate zone.

During the discussion, it was noted that several small-building archetypes in Climate Zone 4 failed the modelling due to cooling rather than heating performance. The group agreed this underscored the limitations of prescriptive energy pathways and noted that cooling-related health and safety considerations are addressed elsewhere in the Code.

Tier 4 was briefly discussed and is expected to assume 1.5 ACH for detached dwellings and 2.0 ACH for attached and multifamily buildings, with blower door testing required. Modelling for Tier 4 has not yet been completed and will be presented at a future meeting.

For more information, please contact alex.bols@chba.ca