9.32.3.11.Ducts (See Note A-9.32.3.11.)

(1) Except as provided in Sentence (6), ventilation ducts and their fittings shall conform to the requirements of Article 9.33.6.2., except that exhaust ducts serving only a bathroom or water-closet room are permitted to be of combustible material, provided they are reasonably airtight and constructed of a material impervious to water. (2) Exhaust ducts shall not discharge into heated or unheated enclosed spaces. (3) Where an exhaust duct passes through an unheated space or is not separated from an unheated space by an insulated building assembly, the duct shall be insulated to not less than RSI 0.5. (4) Where a duct carrying outdoor air that is not tempered and not mixed with indoor air passes through heated space, it shall be (a) insulated to not less than RSI 0.5, and (b) provided with a vapour barrier. (5) All exhaust intakes located within 3 m horizontally of a cooktop shall be equipped with a grease filter at the intake end. (6) Ductwork for cooking appliance exhaust fans shall (a) be of noncombustible, corrosion-resistant material, (b) lead directly to the outdoors with no connections to other exhaust fans or ducts, and (c) be equipped with a grease filter at the intake end. (7) All ductwork shall be installed to avoid crushing and shall be permanently supported to prevent sagging. (8) Joints in all ventilation system ducting shall be sealed with mastic, metal foil duct tape or the manufacturers' specified sealants. (9) Except where the size of a duct can be determined using Table 9.32.3.11.-A or Table 9.32.3.11.-B, duct sizes shall be determined according to Subsection 9.33.4. (10) In using Table 9.32.3.11.-A, (a) when sizing branch ducts, “maximum length of duct” refers to the physical length of the duct from the interior grille served by that branch duct to the exterior hood, (b) when sizing a trunk duct, “maximum length of duct” refers to the physical length of the duct from the interior grille of the longest branch served by that trunk to the exterior hood, (c) outdoor air supply ducts shall be sized as trunk ducts, (d) “maximum airflow in duct” refers to the maximum airflow rate that a given section of duct (branch or trunk) must provide to satisfy the ventilation system design, and (e) “fan's external static pressure” refers to the external static pressure at which the fan is rated to achieve the maximum airflow rate that the fan is required or intended to provide. (11) Where flexible duct is used, it may be sized by choosing the next higher diameter in Table 9.32.3.11.-A or by choosing the diameter for a duct twice as long as the actual length. (12) Where rectangular duct is used in place of round duct, it shall be selected according to Table 9.32.3.11.-B. Table 9.32.3.11.-A Equivalent Duct Sizes Forming Part of Sentence 9.32.3.11.(9) Fan's Maximum Airflow in Duct, L/s External Duct 7 15 25 35 50 75 100 Static Diameter, Pressure, mm Maximum Length of Duct, m Pa 75 6 1 0 0 0 0 0 100 25 6 2 1 0 0 0 125 60 17 6 3 1 0 0 150 60 42 16 8 4 2 1 175 60 60 34 18 9 4 2 200 60 60 60 35 18 8 5 75 16 4 1 0 0 0 0 100 60 16 6 3 1 0 0 125 60 47 18 9 5 2 1 150 60 60 44 23 12 5 3 175 60 60 60 49 25 12 7 200 60 60 60 60 48 22 13 75 22 5 2 1 0 0 0 100 60 21 8 4 2 1 0 125 60 60 24 12 6 3 1 62.5 150 60 60 58 31 15 7 4 175 60 60 60 60 33 15 9 200 60 60 60 60 60 29 17 75 38 9 3 1 0 0 0 100 60 36 14 7 3 1 1 125 60 60 41 22 11 5 3 150 60 60 60 53 27 12 7 175 60 60 60 60 57 27 15 200 60 60 60 60 60 51 30 75 59 14 5 2 1 0 0 100 60 57 22 11 6 2 1 125 60 60 60 34 17 8 4 150 60 60 60 60 42 20 11 175 60 60 60 60 60 42 24 200 60 60 60 60 60 60 46 Table 9.32.3.11.-B Equivalent Duct Sizes Forming Part of Sentences 9.32.3.11.(9) and (12) Permitted Equivalent Rectangular Duct Size, mm Required Round Duct Size, mm Stack Duct 100 mm Depth 125 mm Depth 150 mm Depth 75 75 × 150 50 × 100 — — 100 75 × 250 75 × 100 75 × 125 75 × 150 125 75 × 250 125 × 100 100 × 125 100 × 150 150 75 × 300 200 × 100 150 × 125 125 × 150 175 75 × 350 275 × 100 200 × 125 175 × 150 > 175 Design to Subsection 9.33.4.