For example...
If one of the regions in Canada was starting at Tier 1 as they adopted the 2020 code, when the 2025 National Building Code is published and adopted, their energy performance requirements will move up to Tier 2.
If a builder is following their local code to the letter, building to compliance (a.k.a. using the PRESCRIPTIVE PATH), they will simply follow the new requirements for insulation, air tightness, mechanicals, windows and doors as laid out in the code. Eventually, they will get to point where the code is at Tier 5.
IMPORTANT NOTE:
When meeting Tiers 4 and 5, it will be necessary to MEASURE the energy performance of a building. This means that performing material inspections, air tightness testing and systems commissioning will become a regular part of the process.
Get familiar with programs like Net Zero and Passive House, and build a relationship with an Energy Advisor in your area. Most municipalities in Canada will have "service organizations" that host energy advisors and help them keep track of their work. There are helpful links at Natural Resources Canada (NRCan).