Division B
Acceptable Solutions

Part 9 — Housing and Small Buildings

Section 9.25. Heat Transfer, Air Leakage and Condensation Control

9.25.1. General

9.25.1.1. Scope and Application

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. and Section 9.36.,

ii) an air barrier conforming to Subsection 9.25.3. and Section 9.36.,

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.

NC2010  2010-01-01 R1

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. and Section 9.36.,

ii) an air barrier conforming to Subsection 9.25.3. and Section 9.36.,

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.

3) Insulation and sealing of heating and ventilating ducts shall conform to Sections 9.32., 9.33. and 9.36.

NC2010  2010-01-01 R1

3) Insulation and sealing of heating and ventilating ducts shall conform to Sections 9.32., 9.33. and 9.36.

9.25.2. Thermal Insulation

9.25.2.1. Required Insulation

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 A-9.1.1.1.(1) in Appendix A.)

BC2012  2012-01-01 R1NC2010  2010-01-01 R1

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 A-9.1.1.1.(1) in Appendix A.)A and Part 10)

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 A-9.1.1.1.(1) in Appendix A.)

9.25.2.2. Insulation Materials

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

a) CAN/CGSB-51.25-M, “Thermal Insulation, Phenolic, Faced,”

b) CGSB 51-GP-27M, “Thermal Insulation, Polystyrene, Loose Fill,”

c) CAN/ULC-S701, “Thermal Insulation, Polystyrene, Boards and Pipe Covering,”

d) CAN/ULC-S702, “Mineral Fibre Thermal Insulation for Buildings,”

e) CAN/ULC-S703, “Cellulose Fibre Insulation (CFI) for Buildings,”

f) CAN/ULC-S704, “Thermal Insulation, Polyurethane and Polyisocyanurate, Boards, Faced,”

g) CAN/ULC-S705.1, “Thermal Insulation – Spray Applied Rigid Polyurethane Foam, Medium Density – Material - Specification,” or

h) CAN/ULC-S706, “Wood Fibre Insulating Boards for Buildings.”

NC2010  2010-01-01 R1

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

a) CAN/CGSB-51.25-M, “Thermal Insulation, Phenolic, Faced,”

b) CGSB 51-GP-27M, “Thermal Insulation, Polystyrene, Loose Fill,”

c) CAN/ULC-S701, “Thermal Insulation, Polystyrene, Boards and Pipe Covering,”

d) CAN/ULC-S702, “Mineral Fibre Thermal Insulation for Buildings,”

e) CAN/ULC-S703, “Cellulose Fibre Insulation (CFI) for Buildings,”

f) CAN/ULC-S704, “Thermal Insulation, Polyurethane and Polyisocyanurate, Boards, Faced,”

g) CAN/ULC-S705.1, “Thermal Insulation – Spray Applied Rigid Polyurethane Foam, Medium Density – Material - Specification,” or

h) CAN/ULC-S706, “Wood Fibre Insulating Boards for Buildings.”

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

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

9.25.2.3. Installation of Thermal Insulation

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 Appendix A.)

4) Insulation on the interior of foundation walls enclosing a crawl space shall be applied so that there is not less than 50 mm clearance above the crawl space floor, if the insulation is of a type that may be damaged by water.

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 asbestos-cement board,

b) 6 mm preservative-treated plywood, or

c) 12 mm cement parging on wire lath applied to the exposed face and edge.

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

9.25.2.4. Installation of Loose-Fill Insulation

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 Appendix A.)

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 the 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 Appendix A.)

6) Where soffit venting is used, measures shall be taken

a) to prevent loose-fill insulation from blocking the soffit vents and to maintain an open path for circulation of air from the vents into the attic or roof space, and

b) to minimize airflow into the insulation near the soffit vents to maintain the thermal performance of the material. (See Article 9.19.1.3.)

9.25.2.5. Installation of Spray-Applied Polyurethane

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

9.25.3. Air Barrier Systems

9.25.3.1. Required Barrier to Air Leakage

1) Wall, ceiling and floor assemblies separating 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 Appendix A.)

9.25.3.2. Air Barrier System Properties

(See A-9.25.5.1.(1) in Appendix A.)

1) Air barrier systems shall possess the characteristics necessary to provide an effective barrier to air infiltration and exfiltration under differential air pressure due to stack effect, mechanical systems or wind.

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

9.25.3.3. Continuity of the Air Barrier System

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

2) Except as provided in Sentence 9.25.3.6.(3), where the air barrier system consists of flexible sheet material, all joints shall be

a) sealed, or

b) lapped not less than 100 mm and clamped, such as between framing members, furring or blocking, and rigid panels.

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.

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.

5) Where an interior floor projects through an exterior wall or extends to become an exterior floor, continuity of the air barrier system shall be maintained from the abutting walls across the floor assembly.

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

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 buildingattic or roof space shall be sealed by noncombustible material to prevent such leakage.

9.25.3.4. Air Leakage Control in Masonry Walls

1) Masonry walls required to provide a barrier to the ingress of air from the ground shall

a) include a course of masonry units without voids, or

b) be sealed with flashing material extending across the full width of the masonry.

2) The masonry course or flashing described in Sentence (1) shall

a) be located at the level of the adjoining floor and be sealed to it in accordance with Article 9.25.3.6., or

b) in the absence of a floor, be located at the level of the ground cover required by Article 9.18.6.1. and be sealed to it.

9.25.3.5. Air Leakage Control in Underground Roofs

1) Waterproofing systems for roofs of underground structures shall be sealed to the air barrier in the walls.

9.25.3.6. Air Barrier Systems in Floors-on-ground

1) Materials used to provide a barrier to the ingress of air through floors-on-ground shall conform to CAN/CGSB-51.34-M, “Vapour Barrier, Polyethylene Sheet for Use in Building Construction.”

2) Where the floor-on-ground is a concrete slab, the air barrier shall be

a) installed below the slab, or

b) applied to the top of the slab, provided a separate floor is installed over the slab.

(See A-9.25.3.6.(2) and (3) in Appendix A.)

3) Where the air barrier installed below a floor-on-ground is flexible sheet material, joints in the barrier shall be lapped not less than 300 mm. (See A-9.25.3.6.(2) and (3) in Appendix A.)

4) Where installed in conjunction with a framed floor-on-ground or above a floor-on-ground, the air barrier shall be installed in accordance with Article 9.25.3.3.

5) A floor-on-ground shall be sealed around its perimeter to the inner surfaces of adjacent walls using flexible sealant.

6) All penetrations of a floor-on-ground that are required to drain water from the floor surface shall be sealed in a manner that prevents the upward flow of air without preventing the downward flow of liquid water.

9.25.4. Vapour Barriers

9.25.4.1. Required Barrier to Vapour Diffusion

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.

9.25.4.2. Vapour Barrier Materials

1) Vapour barriers shall have a permeance not greater than 60 ng/(Pa•s•m²) measured in accordance with ASTM E 96/E 96M, “Water Vapor Transmission of Materials,” using the desiccant method (dry cup).

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

3) 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.”

4) 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.”

5) 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.”

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

9.25.4.3. Installation of Vapour Barriers

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. (See Appendix A and A-9.25.5.1.(1) in Appendix A.)

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. (See A-9.25.4.3.(2), A-9.25.5.1.(1) and A-9.25.5.2. in Appendix A.)

9.25.5. Properties and Position of Materials in the Building Envelope

9.25.5.1. General

1) 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,

ii) a water vapour permeance less than 60 ng/(Pa•s•m²) when measured in accordance with ASTM E 96/E 96M, “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.

(See Appendix A.)

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).

9.25.5.2. Position of Low Permeance Materials

(See Appendix A.)

1) Sheet and panel-type materials described in 9.25.5.1. shall be installed

a) on the warm face of the assembly (see also Article 9.25.4.2.),

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 comply with Clause 9.27.2.2.(1)(a).