6.2.4.

(1) The requirements of this Subsection apply to the design, construction and installation of air duct distribution systems serving heating, ventilating and air-conditioning systems that serve individual dwelling units within the scope of Part 9.

(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.

(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.

(1) Rectangular panels in plenums and ducts more than 300 mm wide shall be shaped to provide sufficient stiffness.

(2) Where the installation of heating supply ducts in walls and floors creates a space between the duct and construction material, the space shall be fire stopped with noncombustible material at each end.

(3) Ducts shall be securely supported by metal hangers, straps, lugs or brackets, except that where zero clearance is permitted, wooden brackets may be used.

(4) All round duct joints shall be tight-fitting and lapped not less than 25 mm.

(5) Rectangular duct connections shall be made with S and drive cleats or equivalent mechanical connections.

(6) Trunk supply ducts shall not be nailed directly to wood members.

(7) Branch ducts shall be supported at suitable spacings to maintain alignment and prevent sagging.

(8) Combustible ducts in concrete slabs-on-ground that are connected to a furnace supply plenum shall be located not closer than 600 mm to that plenum and not less than 600 mm from its connection to a riser or register.

(9) Ducts in or beneath concrete slabs-on-ground shall be watertight, corrosion-, decay- and mildew-resistant.

(10) Where a supply or return duct is not protected by an insulated exterior wall or where the duct is exposed to an unheated space it shall be insulated to provide a thermal resistance of not less than RSI 2.1.

(11) Ductwork passing through unconditioned spaces shall have all joints taped or be otherwise sealed to ensure that the ducts are airtight throughout their length.

(12) Underground ducts shall,

(a) be constructed and installed with a slope to provide interior drainage to all low points,

(b) not be connected directly to a sewer, and

(c) be installed and constructed of materials in conformance with ASHRAE Handbooks, SMACNA Manuals and the HRAI Digest.

(13) A clean-out or pump-out connection shall be provided in an underground duct system at every low point of the duct system.

(1) In a dwelling unit, a warm-air supply outlet shall be provided in each finished room that is located adjacent to unheated space, exterior air or exterior soil.

(2) Except as provided in Sentence (3), when a room described in Sentence (1) is located adjacent to exterior walls, such outlets shall be located so as to bathe at least one exterior wall or window with warm air, except in bathrooms, utility rooms or kitchens, where this may not be practical.

(3) Where the heating system is also designed to provide ventilation air, ceiling outlets or outlets located high on interior walls may be installed provided the outlets are,

(a) designed for this purpose, and

(b) installed with diffusers.

(4) At least one warm-air supply outlet shall be provided for each 40 m² of floor surface area in unfinished basements serving dwelling units, located so as to provide adequate distribution of warm air throughout the basement.

(5) At least one warm-air supply outlet shall be provided for each 80 m² of floor surface area in heated crawl spaces serving dwelling units, and it shall be located so as to provide adequate distribution of warm-air throughout the crawl space.

(6) Except for pipeless furnaces and floor furnaces, the capacity of warm-air supply outlets serving dwelling units shall be not less than the design heat loss from the area served and shall not exceed 3 kW per outlet.

(7) In basements and heated crawl spaces, the calculated heat gain from the supply ducts and plenum surfaces may be considered in calculating the design heat loss.

(8) The temperature of supply air at the warm-air supply outlets shall not exceed 70°C.

(9) Warm-air supply outlets located in finished areas shall be provided with diffusers and adjustable openings and shall not be located on a furnace plenum.

(10) Air duct systems serving storage garages shall not be interconnected with other parts of the building.

(1) Warm-air supply systems for buildings of residential occupancy built on concrete slabs-on-ground,

(a) shall be installed in the slab, and

(b) shall be of the perimeter loop type or radial perimeter type.

(1) All branch supply ducts for residential systems shall be equipped with volume control dampers at the boot to permit balancing or shall be fitted with a diffuser incorporating an adjustable and lockable volume control device that can be set in a fixed position.

(1) The return-air system shall be designed to handle the entire air supply.

(2) Except as provided in Sentences (3) and (4), return ducts shall be constructed of material having a surface flame-spread rating of not more than 150.

(3) Where any part of a return duct will be exposed to radiation from the furnace heat exchanger or other radiating part within the furnace, such part of a return duct directly above or within 600 mm of the outside furnace casing shall be noncombustible.

(4) Return ducts serving solid fuel-fired furnaces shall be constructed of noncombustible material.

(5) Combustible return ducts shall be lined with noncombustible material below floor registers, at the bottom of vertical ducts and under furnaces having a bottom return.

(6) Spaces between studs and joists used as return ducts shall be separated from the unused portions of such spaces by tight-fitting metal stops or wood blocking.

(7) A vertical return duct shall have openings to return air on not more than 1 floor.

(8) A public corridor shall comply with Sentences 6.2.3.9.(4)v1 and (5).

(9) The return-air system shall be designed so that the negative pressure from the circulating fan cannot affect the furnace combustion air supply nor draw combustion products from joints or openings in the furnace or flue pipe.

(10) Return-air from a dwelling unit shall not be recirculated to any other dwelling unit.

(11) Except for floor levels that are less than 900 mm above or below an adjacent floor level that is provided with a return-air inlet, at least one return-air inlet shall be provided in each floor level in a dwelling unit.

(12) Provision shall be made for the return of air from all rooms by leaving gaps beneath doors, using louvred doors or installing return duct inlets.

(13) Return-air inlets shall not be installed in an enclosed room or crawl space that provides combustion air to a furnace.

(1) Foamed plastic insulation may be used in a ceiling space that acts as a return air plenum provided the foamed plastic insulation is protected from exposure to the plenum in accordance with Article 3.1.5.12.v1v2

(2) Linings of ducts shall be installed so that they will not interfere with the operation of volume or balancing dampers.

(1) Tape used for sealing joints in air ducts, plenums and other parts of air duct systems shall meet the flame-resistance requirements for fabric in CAN/ULC-S109, “Flame Tests of Flame-Resistant Fabrics and Films”.

(1) Where the plenum clearance is 75 mm or less, the clearance between a supply duct and combustible material shall,

(a) be equal to the required plenum clearance within 450 mm of the plenum, and

(b) be not less than 12 mm at a distance of 450 mm or more from the plenum, except that this clearance may be reduced to zero beyond a bend or offset in the duct sufficiently large to shield the remainder of the duct from direct radiation from the furnace heat exchanger.

(2) Where the plenum clearance is more than 75 mm but not more than 150 mm, the clearance between a supply duct and combustible material shall,

(a) be equal to the required plenum clearance within a horizontal distance of 1 800 mm of the plenum, and

(b) be not less than 12 mm at a horizontal distance of 1 800 mm or more from the plenum, except that this distance may be reduced to zero beyond a bend or offset in the duct sufficiently large to shield the remainder of the duct from direct radiation from the furnace heat exchanger.

(3) Where the plenum clearance is more than 150 mm, the clearance between a supply duct and combustible material shall,

(a) be equal to the required plenum clearance within a horizontal distance of 1 000 mm of the plenum,

(b) be not less than 150 mm within a horizontal distance between 1 000 mm and 1 800 mm from the plenum, and

(c) be not less than 25 mm at a horizontal distance of 1 800 mm or more from the plenum, except that this distance may be reduced to 8 mm beyond a bend or offset in the duct sufficiently large to shield the remainder of the supply duct from direct radiation from the furnace heat exchanger.

(4) Where a register is installed in a floor directly over a pipeless furnace, a double-walled register box with not less than 100 mm between walls, or a register box with the warm-air passage completely surrounded by the cold-air passage, shall be permitted in lieu of the clearances listed in Sentences (1), (2) and (3).

(1) Where an exhaust duct passes through or is adjacent to unheated space, the duct shall be insulated to prevent moisture or condensation in the duct.

(2) Exhaust outlets shall be designed to prevent back draft under wind conditions.

(3) Exhaust ducts directly connected to laundry drying equipment shall be independent of other exhaust ducts.

(4) Exhaust systems shall discharge directly to the outdoors.

(1) In ventilating systems that exhaust air to the outdoors, provision shall be made for the admission of a supply of make-up air in sufficient quantity so that the operation of the exhaust system and other exhaust equipment or combustion equipment is not adversely affected.

(2) Except as provided in Sentence (3), when electric resistance heating is used to temper make-up air required in Sentence (1) in buildings of residential occupancy within the scope of Part 9, the energy rating for windows and sliding glass doors shall conform to the requirements of Article 12.3.2.8. and the minimum thermal resistance of insulation to be installed shall conform to Column 4 of Table 12.3.2.1.

(3) Sentence (2) does not apply where,

(a) electric space heating is provided, or

(b) a heat recovery ventilator meeting the minimum rating requirements of Article 6.2.1.6. is installed.

(1) Supply, return and exhaust air openings in rooms or spaces shall be protected by grilles having openings of a size that will not allow the passage of a 15 mm diameter sphere.

(2) Outdoor air intakes and exhaust outlets at the building exterior shall be designed or located so that the air entering the building system will not contain more contaminants than the normal exterior air.

(3) Exterior openings for outdoor air intakes and exhaust outlets shall be shielded from the entry of snow and rain and shall be fitted with corrosion-resistant screens of mesh not larger than 15 mm, except where climatic conditions may require larger openings.

(4) Screens required in Sentence (3) shall be accessible for maintenance.

(5) Combustible grills, diffusers and other devices for the supply and return air openings installed in walls and ceilings shall have a flame-spread rating of,

(a) not more than 200 in bathrooms, and

(b) not more than 150 in rooms or spaces other than bathrooms.

(1) Air filters for air duct systems shall conform to the requirements for Class 2 air filter units as described in CAN4-S111, “Fire Tests For Air Filter Units”.

(2) When electrostatic-type filters are used, they shall be installed so as to ensure that the electric circuit is automatically de-energized when filter access doors are opened or when the system circulating fan is not operating.

(3) When odour removal equipment of the adsorption type is used it shall be,

(a) installed to provide access so that adsorption material can be reactivated or renewed, and

(b) protected from dust accumulation by air filters installed on the inlet side.