The Ontario Building Code | Duct Design

6.2.4.2. Duct design

(1) Materials in supply ducts shall conform to Article 6.2.3.2.

(2) Galvanized steel or aluminum supply ducts shall conform to Table 6.2.4.2.

Table 6.2.4.2.
Minimum Metal Thickness of Ducts

Forming Part of Sentences 6.2.4.2.(2) and (3)

Item	Column 1	Column 2	Column 3	Column 4	Column 5
	Type of Duct	Maximum Diameter, mm	Maximum Width or Depth, mm	Minimum Metal Thickness, mm
				Duct Material
				Galvanized Steel	Aluminum
1.	Round ducts serving single dwelling units	125 or less	---	0.254	0.30
2.	Round	350	---	0.33	0.30
		over 350	---	0.41	0.41
3.	Rectangular, enclosed	---	350	0.33	0.30
		---	over 350	0.41	0.41
4.	Rectangular, not enclosed, for single dwelling units, with required clearance up to 12 mm	---	350	0.33	0.41
		---	over 350	0.41	0.48
5.	Rectangular, not enclosed, with required clearance of more than 12 mm	---	350	0.41	0.41
		---	over 350	0.48	0.48

Note: On July 1, 2017, Table 6.2.4.2. of Division B of the Regulation is amended by striking out "single dwelling units" in Column 1 of Item 1 and substituting "an individual dwelling unit in a building other than a house", striking out "Round" in Column 1 of Item 2 and substituting "Round ducts serving a house or an individual dwelling unit in a house" and striking out "for single dwelling units" in Column 1 of Item 4. (See: O. Reg. 139/17, s. 52)

(3) The design of fitting for ducts shall conform to SMACNA, "HVAC Duct Construction Standards – Metal and Flexible", except that metal thickness shall conform to Table 6.2.4.2.