How the 2025 National Code Applies to Alterations to Existing Buildings (PDF)

Canada’s aging building stock presents both a challenge and an opportunity. On one hand, inconsistent local renovation rules across Canada create unnecessary complexity and cost challenges for renovators. On the other hand, a clear national framework would present a major opportunity to gradually improve the energy efficiency for 14 million existing homes, rather than having ambitious new energy codes apply to a few hundred thousand new builds every year. Nearly half of Canadian homes were built before 1980, making them less energy-efficient and potentially more climate-vulnerable, and renovations for all kinds of reasons already outpace new construction economically, generating over $122 billion in 2025 and supporting 692,500 jobs.

To address the challenge and capitalize on the opportunity, the 2025 National Building Code (NBC) introduces a new Part 10 that establishes a clear and uniform framework for renovations focusing – for now – entirely on energy efficiency.

Key Principles Used for the 2025 Renovation Code

The code requirements are based on principles that renovators already recognize. Instead of forcing older buildings to meet today’s new‑build standards, the approach is to gradually improve their performance in a cost‑effective and technically sound way, taking advantage of opportunities when renovation work is already happening. Energy efficiency upgrades are meant to be done using the home-as-a-system approach, so renovations meant as improvements do not create moisture, durability, fire safety, or indoor air quality problems. Requirements are intended to match the scope of the work and be realistic to apply, so renovations stay affordable and practical and owners are encouraged to proceed with energy upgrades rather than abandon the project.

Above all, the framework relies on flexibility to deal with existing conditions, technical limits, and cost, and to keep renovations within the regulated system rather than pushing them underground.

When Do the Requirements Apply?

If adopted by the province in which the project is located, the 2025 requirements would apply only to voluntary alterations to a building that is more than five years old and only if the alteration affects a component or assembly that affects a home’s energy efficiency (e.g. exterior walls, furnace, etc.).

Routine maintenance, repair and like-for-like replacements are exempt, ensuring that minor work isn’t subject to full code compliance. The rules do not apply to maintenance or repair work, heritage buildings, or additions, since additions are treated as new construction under other code provisions.

What is actually required

The table below describes the building elements that the new code articles deal with and where requirements can be found. It also summarizes what is required. If work is being done on a home (older than 5 years) and the work falls within the scope of one of these technical areas, renovators would have to comply with the minimum requirements in Part 10 for that specific element:

Important notes on the limits of the new Part 10

Avoiding Scope Creep – Specific code wording was chosen to help avoid scope creep and driving renovations into the underground economy, which states, “the provisions of Part 10 are not intended to require building owners to undertake work beyond the planned extent of an alteration.”

To the Extent Possible – Additionally, the code uses the term “to the extent possible” to provide flexibility for renovators when encountering unique situations or surprises. The Notes to the code explain that “to the extent possible” may – in some cases – mean “may not be possible at all.” One example mentioned in the notes is where a basement stairwell is located against an existing foundation wall, preventing ‘practical’ ways of insulating the wall, because in this case, Part 9 requirements may not permit the addition of exterior insulation and because reconstructing or relocating the stairwell might require significant effort and cost. The concept of the phrase “To the extent possible” is intended to encourage increasing energy efficiency as much as possible within existing limitations. It is important to understand that there will be instances where upgrading, for example, the installation of additional insulation, will not be possible and that this is an acceptable outcome for specific locations.