PART 9 — HOUSING AND SMALL BUILDINGSUpdated for the 2024 Ontario Building Code
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9.7.3.3.Thermal Characteristics of Windows, Doors and Skylights
(1) Metal frames and sash of windows, doors and skylights shall incorporate a thermal break.
(2) Windows and doors described in Sentence (1) do not require a thermal break where they are installed as
(a) vehicular access doors,
(b) storm windows and doors, or
(c) windows and doors that are required to have a fire-resistance rating.
(3) Windows, doors and skylights with or without storm doors or sash that are installed in buildings where the intended
use of the interior space will not result in high moisture generation shall have a maximum thermal transmittance (U-
value) or minimum temperature index (I) in accordance with Table 9.7.3.3.
(4) Windows, doors and skylights, with or without storm doors or sash that are installed in portions of buildings where
the intended use of the interior space will result in high moisture generation shall be designed in conformance with
Subsection 5.3. (See Note A-9.25.5.2.)
Table 9.7.3.3.
Maximum U-value or Minimum Temperature Index (I) for Windows, Doors and Skylights (1)(2)(3)
Forming Part of Sentence 9.7.3.3.(3)
2.5% January Design Temperature
Component Between -15°C and -30°C Colder than -30°C
max. U-value, W/m2K min. I max. U-value, W/m2K min. I
Windows and Doors 2.0 68 1.7 77
Skylights 3.0 (2) 2.7 (2)
Notes to Table 9.7.3.3.:
(1) U-values for specific products can be determined according to measures referenced in AAMA/WDMA/CSA 101/I.S.2/A440,
“NAFS - North American Fenestration Standard/Specification for windows, doors, and skylights.” Temperature index (I) is determined
according to the physical test procedure given in CSA A440.2/A440.3, “Fenestration energy performance/User guide to CSA A440.2-
19, Fenestration energy performance.”
(2) There is no appropriate test procedure available for testing the condensation resistance of sloped glazing.
(3) Where the U-value in this Table differs from the U-value provided in MMA Supplementary Standard SB-10, “Energy Efficiency
Requirements” or MMA Supplementary Standard SB-12, “Energy Efficiency for Housing”, the most restrictive U-value shall apply.
This provision includes a table — formatting is preserved from the source; refer to the official code for the authoritative layout.
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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.