OBC DIVISION B · PART 5 — ENVIRONMENTAL SEPARATIONUpdated for the 2024 Ontario Building Code
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Section 5.3 — Heat Transfer (See Note A-5.3.)
Full text of Section 5.3 (Heat Transfer (See Note A-5.3.)) — Division B, Part 5 (Environmental Separation) of the 2024 Ontario Building Code, with every article reproduced below.
5.3.1.Thermal Resistance of Assemblies
5.3.1.1.Required Resistance to Heat Transfer (See Note A-5.3.1.1.) permalink →
(1) Except as provided in Sentence (2), where a building component or assembly will be subjected to an intended
temperature differential, the component or assembly shall include materials to resist heat transfer or a means to dissipate
transferred heat in accordance with the remainder of this Subsection.
(2) The installation of materials to resist heat transfer in accordance with this Subsection is not required where it can be
shown that uncontrolled heat transfer will not adversely affect any of
(a) the health or safety of building users,
(b) the intended use of the building, or
(c) the operation of building services.
5.3.1.2.Properties to Resist Heat Transfer or Dissipate Heat (See Note A-5.3.1.2.) permalink →
(1) Taking into account the conditions on either side of the environmental separator, materials and components installed
to provide the required resistance to heat transfer or the means implemented to dissipate heat shall provide sufficient
resistance or dissipation,
(a) to minimize surface condensation on the warm side of the component or assembly,
(b) in conjunction with other materials and components in the assembly, to minimize condensation within the
component or assembly,
(c) in conjunction with systems installed for space conditioning, to meet the interior design thermal conditions for the
intended occupancy, and
(d) to minimize ice damming on sloped roofs.
(See Note A-5.3.1.2.(1))
5.3.1.3.Location and Installation of Materials Providing Thermal Resistance permalink →
(1) Where a material required by Article 5.3.1.1. is intersected by a building assembly, penetrated by a high conductance
component or interrupted by expansion, control or construction joints, and where condensation is likely to occur at these
intersections, penetrations or interruptions, sufficient thermal resistance shall be provided so as to minimize condensation
at these locations.
(2) Materials providing required thermal resistance shall have sufficient inherent resistance to airflow or be positioned in
the assembly so as to prevent convective airflow through and around the material. (See Note A-5.3.1.3.(2))
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Code text is reproduced for reference from the Ontario Building Code (O. Reg. 163/24, 2024 Building Code Compendium). This page is provided for general information and is not an official copy. Always verify requirements against the official Ontario Building Code and confirm with your local building department.