Canada · Energy & envelope

What are the building code requirements for foam plastic insulation in Canada?

Foam plastic insulation in Canada must be separated from interior spaces by an approved thermal barrier unless the assembly qualifies for a specific exception, and exterior use requires verified flame-spread and fire-propagation performance under the relevant code provisions.

Foam plastics — including expanded polystyrene, extruded polystyrene, polyurethane, and polyisocyanurate — are excellent insulators but flammable. The code therefore requires layered protection, and the details of acceptable thermal barriers and exposed-foam exceptions are where designs frequently get tripped up.

What to check first

  • Confirm the thermal barrier requirement for any interior-side foam plastic insulation.
  • Verify the foam product has the required fire-performance documentation for its assembly.
  • Identify any exceptions that allow exposed foam, such as specific attic, crawl space, or industrial conditions.

Jurisdiction notes

NBC foam plastic provisions

Part 3 and Part 9 of the NBC set distinct foam plastic protection requirements depending on building scope.

Exterior foam needs verified performance

Foam plastic used outside of fire-resistance-rated assemblies requires CAN/ULC-S134 or similar verified fire performance.

Provincial adoption is broadly consistent

Foam plastic provisions are among the more uniformly adopted parts of the NBC across provinces.

Not professional advice

CodeCan reports what the published building code says. It is not legal, engineering, or architectural advice, and it does not certify compliance. Building codes are adopted and amended provincially and enforced locally — always verify with your authority having jurisdiction (AHJ) before you build.

Work through it in this order

  1. Identify each location where foam plastic is proposed and its fire-exposure context.
  2. Confirm the required thermal barrier — typically gypsum board of a specified thickness — or qualifying exception.
  3. Check the foam product's tested performance against the assembly classification.
  4. Detail penetrations and edges to maintain the thermal barrier continuity.
  5. Document the substantiating fire-performance reports for permit review.

Common questions

Can foam plastic insulation be left exposed?

Only in specific conditions and assemblies allowed by the code; otherwise an approved thermal barrier is required.

What qualifies as a thermal barrier?

Typically 12.7 mm gypsum board or an assembly tested to provide equivalent fire resistance for the foam plastic involved.

Does foam plastic on the exterior face additional requirements?

Yes. Exterior use commonly requires CAN/ULC-S134 testing or other verified flame-spread and fire-propagation performance.