Insulation R-Values in Canada: R, RSI and Regional Verification

RSI = US R × 0.1761101838. For example, R-20 corresponds to RSI 3.522, and R-40 corresponds to RSI 7.044. An SI U-value is 1 / RSI; taking 1 / US R returns a US U-factor instead. Always preserve the unit labels when comparing product sheets or assembly calculations.

NRCan’s Keeping the Heat In resources discuss materials, walls, attics, basements and air sealing. They help explain retrofit strategies and thermal boundaries. They do not turn one entered cavity value into a locally approved whole-wall assembly.

Determine the building type, location, regulatory edition and compliance pathway that apply. Provincial or territorial adoption, local amendments and project scope can affect requirements. This guide deliberately does not invent a national minimum R-value database. Use the project’s specified target in the calculator.

Separate cavity resistance from continuous insulation and framing heat paths. A batt label is not a whole-wall resistance, and a product sheet’s R-value must correspond to its actual thickness and application.

Use net surfaces and labeled coverage for packs, chart constraints for loose fill, sheets per layer for rigid boards, or board feet for foam. Canadian region selection uses CAD and metric dimensions, while fields labeled US R retain their thermal unit. This keeps geometry conversion independent of regulatory assumptions. Confirm moisture control, rim transitions and air sealing alongside the material order.