The Ontario Building Code | Position of Low Permeance Materials Position of Low Permeance Materials

(1) Sheet and panel-type materials described in Article shall be installed,

(a) on the warm face of the assembly,

(b) at a location where the ratio between the total thermal resistance of all materials outboard of its innermost impermeable surface and the total thermal resistance of all materials inboard of that surface is not less than that required by Table, or

(c) outboard of an air space that is vented to the outdoorref ="" title ="Toronto Door installer">doors.

Ratio of Outboard to Inboard Thermal Resistance

Forming Part of Sentence


Column 1

Heating Degree Days of building Location(1), Celsius Degree-days

Column 2

Minimum Ratio, Total Thermal Resistance Outboard of Material’s Inner surface to Total Thermal Resistance Inboard of Material’s Inner surface


Up to 4 999



5 000 to 5 999



6 000 to 6 999



7 000 to 7 999


Notes to Table

(1) See MMAH Supplementary Standard SB-1, "Climatic and Seismic Data".

(2) For walls, the air space described in Clause (1)(c) shall be drained and ventilated and shall be not less than 10 mm deep behind the cladding, over the full height and width of the wall.

Section 9.26. Roofing

9.26.1. General