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OBC DIVISION B · PART 9 · SECTION 9.25 — HEAT TRANSFER, AIR LEAKAGE AND CONDENSATION CONTROL

What are the insulation installation requirements in the Ontario Building Code?

Insulation must fill its space uniformly, fit snugly against the air barrier and framing without gaps or compression, and be protected from wind washing, moisture and physical damage. Clearances must be kept from heat sources such as chimneys and non-IC-rated recessed fixtures. Required R-values come from SB-12.

Code reference
Thermal insulation must be installed so it provides the intended resistance: continuous contact with the adjacent air barrier, full coverage without voids or excessive compression, protection from precipitation and air movement at exposed edges, and maintained clearances around chimneys, flues and heat-producing devices. Exposed foamed plastics require a protective covering, and supplementary Ontario standards set the required insulation levels.
OBC Division B, Subsection 9.25.2.

Paraphrased for clarity — open this provision in the BUILDAiD Library for the exact wording.

What this means in practice

Installation quality routinely matters more than nominal R-value: a batt with 5 percent voids or gaps at its edges loses a disproportionate share of performance, which is why inspectors look for full-width friction fit, split batts around wiring, and insulation behind tubs and stairs installed before enclosure. Foam plastics need a thermal barrier like 12.7 mm gypsum on the interior, and exterior foam changes vapour dynamics, tying into the low-permeance placement rules. In Ontario, the actual R-value targets, such as roughly R-60 attics and R-22-plus effective walls, come from Supplementary Standard SB-12 compliance packages.

Plain language

Insulation only works when it completely fills the space, no gaps, no squashing it flat, and no wind blowing through its edges. Keep it clear of hot things like chimneys and older pot lights, and get the awkward spots, behind tubs and in corners, insulated before they get sealed up forever.

Related questions

What are the attic insulation rules for houses in Ontario?Does polyethylene have to go on the warm side of the wall in Ontario?

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This page is provided for general information. Building code requirements depend on your specific project, occupancy and municipality, and code editions change. Always verify requirements against the current Ontario Building Code and confirm with your local building department.