Heat Transfer, Air Leakage and Condensation Control

(1)This Section is concerned with heat, air and water vapour transfer and measures to control condensation.

(2)All walls, ceilings and floors separating conditioned space from unconditioned space, the exterior air or the ground shall be

• (a) provided with (i) thermal insulation conforming to Subsection 9.25.2., (ii) an air barrier system conforming to Subsection 9.25.3., and (iii) a vapour barrier conforming to Subsection 9.25.4., and
• (b) constructed in such a way that the properties and relative position of all materials conform to Subsection 9.25.5. (See Note A-9.25.1.1.(2))

(3)Insulation and sealing of heating and ventilating ducts shall conform to Sections 9.32., 9.33.

(1)All walls, ceilings and floors separating heated space from unheated space, the exterior air or the exterior soil shall be provided with sufficient thermal insulation to prevent moisture condensation on their room side during the winter and to ensure comfortable conditions for the occupants. (See Note A-9.1.1.1.(1))

(1)Except as required in Sentence (2), thermal insulation shall conform to the requirements of

• (a) ASTM C726, "Standard Specification for Mineral Wool Roof Insulation Board,"
• (b) CAN/CGSB-51.25-M, "Thermal Insulation, Phenolic, Faced,"
• (c) CGSB 51-GP-27M, "Thermal Insulation, Polystyrene, Loose Fill,"
• (d) CAN/ULC-S701.1, "Standard for Thermal Insulation, Polystyrene Boards,"
• (e) CAN/ULC-S702.1, "Standard for Mineral Fibre Thermal Insulation for Buildings, Part 1: Material Specification,"
• (f) CAN/ULC-S703, "Standard for Cellulose Fibre Insulation (CFI) for Buildings,"
• (g) CAN/ULC-S704.1, "Standard for Thermal Insulation, Polyurethane and Polyisocyanurate, Boards, Faced,"
• (h) CAN/ULC-S705.1, "Standard for Thermal Insulation - Spray Applied Rigid Polyurethane Foam, Medium Density - Material – Specification," or
• (i) CAN/ULC-S706.1, "Standard for Wood Fibre Insulating Boards for Buildings."

(2)The flame-spread rating requirements contained in the standards listed in Sentence (1) shall not apply. (See Note A-9.25.2.2.(2))

(3)Insulation in contact with the ground shall be inert to the action of soil and water and be such that its insulative properties are not significantly reduced by moisture.

(4)Type 1 expanded polystyrene insulation as described in CAN/ULC-S701.1, "Standard for Thermal Insulation, Polystyrene Boards," shall not be used as roof insulation applied above the roofing membrane.

(1)Insulation shall be installed so that there is a reasonably uniform insulating value over the entire face of the insulated area.

(2)Insulation shall be applied to the full width and length of the space between furring or framing.

(3)Except where the insulation provides the principal resistance to air leakage, thermal insulation shall be installed so that at least one face is in full and continuous contact with an element with low air permeance. (See Note A-9.25.2.3.(3))

(4)Insulation shall be installed over the full height of foundation walls enclosing a basement or heated crawl space.

(5)Insulation around concrete slabs-on-ground shall be located so that heat from the building is not restricted from reaching the ground beneath the perimeter, where exterior walls are not supported by footings extending below frost level.

(6)Where insulation is exposed to the weather and subject to mechanical damage, it shall be protected with not less than

• (a) 6 mm preservative-treated plywood, or
• (b) 12 mm cement parging on wire lath applied to the exposed face and edge.

(7)Except as permitted in Sentence (7.1), insulation and vapour barrier located in areas where it may be subject to mechanical damage shall be protected by a covering such as gypsum board, plywood, particleboard, OSB, waferboard or hardboard.

(8)In unfinished basements, the protection required in Sentence (7) need not be provided for mineral fibre insulation, provided it is covered with a membrane which complies with the requirements of Section 9.25.4.

(9)Insulation in factory-built buildings shall be installed so that it will not become dislodged during transportation.

(1)Except as provided in Sentences (2) to (6), loose-fill insulation shall be used on horizontal surfaces only.

(2)Where loose-fill insulation is installed in an unconfined sloped space, such as an attic space over a sloped ceiling, the supporting slope shall not be more than

• (a) 4.5 in 12 for mineral fibre or cellulose fibre insulation, and
• (b) 2.5 in 12 for other types of insulation.

(3)Loose-fill insulation is permitted to be used in wood-frame walls of existing buildings. (See Note A-9.25.2.4.(3))

(4)Where blown-in insulation is installed in above-ground or below-ground wood-frame walls of new buildings,

• (a) the density of the installed insulation shall be sufficient to preclude settlement,
• (b) the insulation shall be installed behind a membrane that will permit visual inspection prior to installation of the interior finish,
• (c) the insulation shall be installed in a manner that will not interfere with the installation of the interior finish, and
• (d) no water shall be added to the insulation, unless it can be shown that the added water will not adversely affect other materials in the assembly.

(5)Water repellent loose-fill insulation is permitted to be used between the outer and inner wythes of masonry cavity walls. (See Note A-9.25.2.4.(5))

(1)Spray-applied polyurethane insulation shall be installed in accordance with CAN/ULC-S705.2, "Standard for Thermal Insulation – Spray-Applied Rigid Polyurethane Foam, Medium Density – Application."

(1)Wall, ceiling and floor assemblies that separate conditioned space from unconditioned space or from the ground shall be constructed so as to include an air barrier system that will provide a continuous barrier to air leakage

• (a) from the interior of the building into wall, floor, attic or roof spaces sufficient to prevent excessive moisture condensation in such spaces during the winter, and
• (b) from the exterior or the ground inward sufficient to (i) prevent moisture condensation on the room side during winter, (ii) ensure comfortable conditions for the occupants, and (iii) minimize the ingress of soil gas. (See Note A-9.25.3.1.(1))

(2)The continuity of the air barrier system shall extend throughout the basement.

(1)Sheet and panel type materials intended to provide the principal resistance to air leakage shall have an air leakage characteristic not greater than 0.02 L/(s∙m2) measured at an air pressure differential of 75 Pa.

(2)Where polyethylene sheet is used to provide the airtightness in the air barrier system, it shall conform to CAN/CGSB-51.34-M, "Vapour Barrier, Polyethylene Sheet for Use in Building Construction."

(1)Where the air barrier system consists of an air-impermeable panel-type material, all joints shall be sealed to prevent air leakage.

(2)Where the air barrier system consists of flexible sheet material, all joints shall be

• (a) sealed with compatible material such as tape or flexible sealant, or
• (b) except as required by Sentence (2.1), lapped not less than 100 mm and clamped, such as between framing members, furring or blocking, and rigid panels.

(2.1)Where an air barrier system consisting of flexible sheet material is installed at locations where it is not supported by an interior finish, such as a behind a bathtub, shower enclosure or fireplace, the continuity of the air barrier shall be maintained by sealing its joints.

(3)Where an interior wall meets an exterior wall, ceiling, floor or roof required to be provided with air barrier protection, the air barrier system shall extend across the intersection and shall be sealed in accordance with Sentences (1) and (2).

(4)Where an interior wall projects through a ceiling or extends to become an exterior wall, spaces in the wall shall be blocked to provide continuity across those spaces with the air barrier system in the abutting walls or ceiling by

• (a) sealing each air barrier to the blocking, or
• (b) wrapping each air barrier around the transition and sealing in accordance with Sentences (1) and (2).

(5)Where an interior floor projects through an exterior wall to become an exterior floor,

• (a) the air barrier of the wall under the floor shall be continuous with or sealed to the subfloor or the air barrier on the underside of the floor,
• (b) the air barrier of the wall above the floor shall be continuous with or sealed to the subfloor or the air barrier on the top of the floor, and
• (c) the spaces between floor joists shall be blocked and sealed.

(5.1)Where a header wrap is used as an air barrier, it shall be sealed or lapped to the wall air barrier above and below in accordance with Sentences (1) and (2).

(6)Penetrations of the air barrier system, such as those created by the installation of electrical wiring, electrical boxes, piping or ductwork, shall be sealed to maintain the integrity of the air barrier system over the entire surface.

(6.1)Where an interior air barrier is penetrated by doors, windows and other fenestration, the air barrier shall be sealed to the door frame or window frame with

• (a) compatible tape, or
• (b) spray foam insulation.

(6.2)Where an exterior air barrier is penetrated by doors, windows and other fenestration, the air barrier shall be sealed to the door frame or window frame with

• (a) compatible flexible flashing material,
• (b) caulking, or
• (c) spray foam insulation.

(7)Where access hatches and sump pit covers are installed through assemblies constructed with an air barrier system, they shall be weatherstripped around their perimeters to prevent air leakage.

(8)Clearances between chimneys or gas vents and the surrounding construction that would permit air leakage from within the building into a wall or attic or roof space shall be sealed by noncombustible material to prevent such leakage and shall be sealed to the air barrier with tape or another compatible material, and to the vent with high temperature caulking in accordance with the manufacturer's installation instructions.

(9)Reserved.

(10)Sump pit covers shall be sealed to maintain continuity of the air barrier system.

(1)A vapour barrier used as an air barrier shall comply with the requirements of this Subsection.

(1)Thermally insulated wall, ceiling and floor assemblies shall be constructed with a vapour barrier so as to provide a barrier to diffusion of water vapour from the interior into wall spaces, floor spaces or attic or roof spaces.

(1)Except as provided in Sentence (2), vapour barriers shall have a permeance not greater than 60 ng/(Pa×s×m2) measured in accordance with ASTM E96 / E96M, "Standard Test Methods for Water Vapor Transmission of Materials," using the desiccant method (dry cup).

(2)Thermally insulated foundation wall assemblies are permitted to be constructed with variable-permeance vapour barriers having a permeance not greater than 60 ng/(Pa×s×m2) using the desiccant method (dry cup) and greater than 300 ng/(Pa×s×m2) using the water method (wet cup) measured in accordance with ASTM E96 / E96M, "Standard Test Methods for Water Vapor Transmission of Materials."

(3)Where the intended use of the interior space will result in high moisture generation, the assembly shall be designed according to Part 5.

(4)Where polyethylene is installed to serve only as the vapour barrier, it shall comply with Clause 4.4, Thermal Stability, and Clause 5.7, Oxidative Induction Time, of CAN/CGSB-51.34-M, "Vapour Barrier, Polyethylene Sheet for Use in Building Construction."

(5)Membrane-type vapour barriers other than polyethylene shall conform to the requirements of CAN/CGSB-51.33-M, "Vapour Barrier, Sheet, Excluding Polyethylene, for Use in Building Construction."

(6)Membrane-type vapour barriers other than polyethylene that are susceptible to deterioration under prolonged exposure to direct ultraviolet radiation shall

• (a) be covered, or
• (b) only be installed in locations that are not exposed to direct ultraviolet radiation after the completion of construction.

(7)Where a coating is applied to gypsum board to function as the vapour barrier, the permeance of the coating shall be determined in accordance with CAN/CGSB-1.501-M, "Method for Permeance of Coated Wallboard."

(8)Where insulation functions as the vapour barrier, it shall be sufficiently thick so as to meet the requirement of Sentence (1).

(1)Products installed to function as the vapour barrier shall protect the warm side of wall, ceiling and floor assemblies.

(2)Where different products are used for the vapour barrier and the insulation, the vapour barrier shall be installed sufficiently close to the warm side of the insulation to prevent condensation at design conditions.

(3)Where the same product is used for the vapour barrier and the insulation, the product shall be installed sufficiently close to the warm side of the assembly to prevent condensation at design conditions.

(1)Except as provided in Sentences (2) to (4), sheet and panel-type materials incorporated into assemblies described in Article 9.25.1.1. shall conform to Article 9.25.5.2. where

• (a) the material has (i) an air leakage characteristic less than 0.1 L/(s×m2) at 75 Pa, and (ii) a water vapour permeance less than 60 ng/(Pa×s×m2) when measured in accordance with ASTM E96 / E96M, "Standard Test Methods for Water Vapor Transmission of Materials," using the desiccant method (dry cup), and
• (b) the intended use of the interior space where the materials are installed will not result in high moisture generation.

(2)Where the intended use of the interior space will result in high moisture generation, the assembly shall be designed according to Part 5.

(3)Wood-based sheathing materials not more than 12.5 mm thick and complying with Article 9.23.17.2. need not comply with Sentence (1).

(4)Where a material has a water vapour permeance not less than 30 ng/(Pa×s×m2) and a thermal resistance not less than 0.7 (m2×K)/W and the heating degree-days of the building location are less than 6000, the assembly need not comply with Sentence (1).

(1)Sheet and panel-type materials described in Article 9.25.5.1. 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 9.25.5.2., or
• (c) outboard of an air space that is vented to the outdoors.

(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.