Heat transfer, air leakage, condensation and energy efficiency (House)

Last updated October 22, 2026

Values this chapter turns on

max vapour barrier permeance, ng/(Pa·s·m²): 60; max vapour barrier permeance, ng/(Pa·s·m²)
min margin over Dec 31, 2024 Code levels: 15%; min margin over Dec 31, 2024 Code levels
glazing ratio: over this, performance only: 22%; glazing ratio: over this, performance only
min lap for clamped air barrier sheets: 100 mm; min lap for clamped air barrier sheets

This section covers how a house envelope controls heat, air and water vapour (Section 9.25.) and how Part 12 and Supplementary Standard SB-12 set the energy efficiency level of a new house. Expect questions on insulation installation details, air barrier continuity, vapour barrier permeance, the outboard-to-inboard ratio table, and the SB-12 compliance routes.

The starting point is OBC Div. B 9.25.1.1.: every wall, ceiling and floor that separates conditioned space from unconditioned space, the outdoors or the ground needs three things. It needs insulation (9.25.2.), an air barrier system (9.25.3.) and a vapour barrier (9.25.4.). The materials must also sit in the right order (9.25.5.). "Conditioned space" is a defined term in Div. A 1.4.1.2.: space whose temperature is controlled by heating or cooling over much of the year.

Thermal insulation

The insulation rules in Subsection 9.25.2. are about where and how, not how much. The amount comes from SB-12.

Insulation must give a reasonably even value over the whole area and fill the full width and length of the framing space (9.25.2.3.).
Unless the insulation is itself the air barrier, one face must be in full contact with a low air permeance element.
Basement and heated crawl space foundation walls are insulated over their full height.
Insulation exposed to the weather and to damage gets at least 6 mm preservative-treated plywood or 12 mm cement parging on wire lath.
Insulation and vapour barrier that could be damaged get a covering such as gypsum board or plywood. The exception: in an unfinished basement, mineral fibre covered by a complying membrane needs no covering.
Insulation touching the ground must resist soil and water and keep its value when wet (9.25.2.2.). Type 1 expanded polystyrene may not go above a roofing membrane.

Loose fill has its own article, 9.25.2.4.. It is for horizontal surfaces, with these limits on unconfined slopes:

Loose-fill type	Steepest unconfined supporting slope
Mineral fibre or cellulose fibre	4.5 in 12
Other loose fill	2.5 in 12

Blown-in insulation in walls of new buildings must be dense enough not to settle and must be installed behind a membrane so it can be inspected before the finish goes on. Where soffit vents are used, the fill must not block them, and wind washing near the vents must be limited.

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Air barrier systems

An air barrier system is "the assembly installed to provide a continuous barrier to the movement of air" (Div. A 1.4.1.2.). 9.25.3.1. requires it wherever an assembly separates conditioned space from unconditioned space or the ground, and continuity must extend through the basement. Sheet and panel materials meant to be the main air barrier must have an air leakage characteristic of no more than 0.02 L/(s·m²) at 75 Pa (9.25.3.2.).

Continuity is the heart of 9.25.3.3.:

Panel joints are sealed.
Flexible sheet joints are sealed with tape or sealant, or lapped at least 100 mm and clamped between framing and rigid panels.
Where the sheet is not backed by an interior finish (behind a tub, shower or fireplace), joints must be sealed. Lapping is not enough there.
At interior wall intersections, the air barrier crosses the joint and is sealed.
Penetrations for wires, boxes, pipes and ducts are sealed. Windows and doors are sealed to the frame with tape or spray foam (interior barrier) or flashing, caulking or foam (exterior barrier).
Access hatches and sump pit covers are weatherstripped. Sump covers are sealed.
Gaps around chimneys and gas vents are sealed with noncombustible material.

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Vapour barriers and position of materials

9.25.4.2. sets the key number: a vapour barrier may have a permeance of no more than 60 ng/(Pa·s·m²), dry cup method. Foundation walls may use a variable-permeance product that meets 60 dry cup and is above 300 wet cup. If the room will generate high moisture, the assembly must be designed under Part 5. The vapour barrier goes on the warm side (9.25.4.3.), close enough to the warm face of the insulation to prevent condensation.

The trap in this subsection is a low-permeance material on the cold side, such as foil-faced foam sheathing. 9.25.5.1. captures sheet and panel materials with an air leakage characteristic below 0.1 L/(s·m²) and a permeance below 60. Exemptions:

wood-based sheathing no more than 12.5 mm thick that complies with 9.23.17.2.
a material with permeance of at least 30 and RSI of at least 0.7, where the location has fewer than 6,000 heating degree-days.

Captured materials must go on the warm face, outboard of a vented air space (at least 10 mm deep behind wall cladding), or at a point where the outboard-to-inboard thermal resistance ratio meets Table 9.25.5.2. (9.25.5.2.). A few rows:

Heating degree-days	Minimum outboard/inboard ratio
Up to 4,999	0.20
5,000 to 5,999	0.30
6,000 to 6,999	0.35

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Part 12 and SB-12

Part 12 applies to resource conservation in all buildings (12.1.1.2.). For a house the key Sentence is 12.2.1.2.(3). A Part 9 residential building occupied through the winter must either beat the December 31, 2024 Code levels by at least 15%, or conform to Chapters 1 and 3 of SB-12. Farm buildings, buildings using no electricity or fossil fuel, and seasonal recreational buildings under 9.37. or 9.39. are exempt.

Section 12.3. adds direct requirements for houses:

Thermostats (12.3.1.3.): each dwelling unit, including each unit in a house with a secondary suite, gets a programmable thermostat. It must allow at least four time periods a day and two day-types a week, a manual override, and setback to 13°C or lower. Solid fuel and ground source heat pump heating are exempt. A manual thermostat is allowed for systems of 2 kW or less or a single room.
Hot water piping (12.3.1.4.): heat traps on tank piping, and RSI 0.62 insulation on the first 2.5 m of outlet piping of a non-recirculating tank.
Furnaces (12.3.1.5.): a furnace serving one dwelling unit needs a brushless DC motor.
Kitchen and laundry (12.3.1.6.): an electrical outlet, gas line or propane line for cooking and drying.

SB-12 gives three routes (SB-12 1.1.1.3.): prescriptive packages (3.1.1.), performance compliance (3.1.2.) or other methods such as ENERGY STAR or R-2000 (3.1.3.). Under the prescriptive route (SB-12 3.1.1.1.), Zone 1 is under 5,000 degree-days and Zone 2 is 5,000 or more. The window-to-wall ratio decides what you can use:

Glazing area / gross peripheral wall area	Route
17% or less	Any package for the zone
Over 17% to 22%	Package, with fenestration U-value upgraded one step
Over 22%	Performance compliance (3.1.2.) only

Other items to know: every dwelling unit needs an HRV or ERV, and rim joist insulation must match the above-grade wall value. One exterior door system per dwelling unit may fall below the RSI 0.7 door minimum (SB-12 3.1.1.10.). Drain water heat recovery is required where showers have a storey or crawl space below them, with at least 42% efficiency (SB-12 3.1.1.12.).

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Water efficiency

12.4.1.1. is one line: all buildings meet the water efficiency rules in Subsection 7.6.4. of Part 7.

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Common traps

Mixing up the 60 dry cup permeance (vapour barrier) with the 30 permeance in the 9.25.5.1.(4) exemption.
Allowing lapped and clamped poly behind a bathtub. Joints there must be sealed.
Using the 13% figure from 12.2.1.2.(2). Houses use 15%.
Forgetting to count the low-permeance layer itself as outboard resistance in the ratio check.

Chapter review

Chapter at a glance

One line per section: the idea to carry into the exam. Then the answers that most often catch candidates out.

Chapter at a glance: the key idea in each section
Section	Key idea
Thermal insulation	The insulation rules in Subsection 9.25.2. are about where and how, not how much.
Air barrier systems	An air barrier system is "the assembly installed to provide a continuous barrier to the movement of air".
Vapour barriers and position of materials	The trap in this subsection is a low-permeance material on the cold side, such as foil-faced foam sheathing.
Part 12 and SB-12	Part 12 applies to resource conservation in all buildings.

Thermal insulation
The insulation rules in Subsection 9.25.2. are about where and how, not how much.
Air barrier systems
An air barrier system is "the assembly installed to provide a continuous barrier to the movement of air".
Vapour barriers and position of materials
The trap in this subsection is a low-permeance material on the cold side, such as foil-faced foam sheathing.
Part 12 and SB-12
Part 12 applies to resource conservation in all buildings.

Usual exam traps

Mixing up the 60 dry cup permeance (vapour barrier) with the 30 permeance in the 9.25.5.1.(4) exemption.
Allowing lapped and clamped poly behind a bathtub. Joints there must be sealed.
Using the 13% figure from 12.2.1.2.(2). Houses use 15%.
Forgetting to count the low-permeance layer itself as outboard resistance in the ratio check.

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Questions on Heat transfer, air leakage, condensation and energy efficiency, in the exam format, every answer explained and cited to its article. Sign in to start; a free account gets the free questions.

Practice this chapter House calculations

Code cited in this chapter

Based on the official 2024 Building Code Compendium on ontario.ca.

OBC Div. B 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.,
(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.
Open OBC Div. B 9.25.1.1. in the code viewer
OBC Div. A 1.4.1.2.(1) Conditioned space
Conditioned space means any space within a building, the temperature of which is controlled to limit variation in response to the exterior ambient temperature by the provision, either directly or indirectly, of heating or cooling over substantial portions of the year.
Open OBC Div. A 1.4.1.2.(1) in the code viewer
OBC Div. B 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 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.
(7.1)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.
(8)Insulation in factory-built buildings shall be installed so that it will not become dislodged during transportation.
Open OBC Div. B 9.25.2.3. in the code viewer
OBC Div. B 9.25.2.2. Insulation Materials
(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-27 M, "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.
Open OBC Div. B 9.25.2.2. in the code viewer
OBC Div. B 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 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))
(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.)
Open OBC Div. B 9.25.2.4. in the code viewer
OBC Div. A 1.4.1.2.(1) Air barrier system
Air barrier system means the assembly installed to provide a continuous barrier to the movement of air.
Open OBC Div. A 1.4.1.2.(1) in the code viewer
OBC Div. B 9.25.3.1. Required Barrier to Air Leakage
(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.
Open OBC Div. B 9.25.3.1. in the code viewer
OBC Div. B 9.25.3.2. Air Barrier System Properties)
(1)Sheet and panel type materials intended to provide the principal resistance to air leakage shall have an air leakage characteristic not greater than 0.02L/(s · m^2) 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."
Open OBC Div. B 9.25.3.2. in the code viewer

Show all 25 articles

OBC Div. B 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)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.
Open OBC Div. B 9.25.3.3. in the code viewer
OBC Div. B 9.25.4.2. Vapour Barrier Materials
(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 / E96 M, "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 / E96 M, "Standard Test Methods for Water Vapor Transmission of Materials." (See Note A-9.25.4.2.(2))
(3)Where the intended use of the interior space will result in high moisture generation, the assembly shall be designed according to Part 5. (See Note A-9.25.4.2.(3))
(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. (See Note A-9.25.4.2.(6))
(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).
Open OBC Div. B 9.25.4.2. in the code viewer
OBC Div. B 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 Note A-9.25.4.3.(2) and A-9.25.5.1.(1))
(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 Note A-9.25.4.3.(2) , A-9.25.5.1.(1) and A-9.25.5.2.)
Open OBC Div. B 9.25.4.3. in the code viewer
OBC Div. B 9.25.5.1. General
(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 0.1L/(s × m^2) at 75 Pa, and
(ii)a water vapour permeance less than 60 ng/(Pa×s×m²) when measured in accordance with ASTM E96 / E96 M, "Standard Test Methods for Water Vapor Transmission of Materials," using the desiccant method (dry cup), and (See Note A-9.25.5.1.(1) (a)(ii))
(b)the intended use of the interior space where the materials are installed will not result in high moisture generation. (See Note A-9.25.5.1.(1))
(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). (See Note A-9.25.5.1.(3))
(4)Where a material has a water vapour permeance not less than 30 ng/( Pa × s × m^2 ) and a thermal resistance not less than 0.7 ( Pa × s × m^2 ) and the heating degree-days of the building location are less than 6000, the assembly need not comply with Sentence (1).
Open OBC Div. B 9.25.5.1. in the code viewer
OBC Div. B Table 9.25.5.2. Ratio of Outboard to Inboard Thermal Resistance — Forming Part of Sentence 9.25.5.2.(1)
Table 9.25.5.2. Ratio of Outboard to Inboard Thermal Resistance — Forming Part of Sentence 9.25.5.2.(1) Forming Part of Sentence 9.25.5.2.(1) Heating Degree Days of Building Location[1], Celsius Degree-Days | Minimum Ratio, Total Thermal Resistance Outboard of Material's Inner Surface to Total Thermal Resistance Inboard of Material's Inner Surface Up to 4,999 | 0.20 5,000 to 5,999 | 0.30 6,000 to 6,999 | 0.35 7,000 to 7,999 | 0.40 8,000 to 8,999 | 0.50 9,000 to 9,999 | 0.55 10,000 to 10,999 | 0.60 11,000 to 11,999 | 0.65 12,000 or higher | 0.75 Notes to Table 9.25.5.2.: (1) See MMAH Supplementary Standard SB-1, "Climatic and Seismic Data."
Open OBC Div. B Table 9.25.5.2. in the code viewer
OBC Div. B 9.25.5.2. Position of Low Permeance Materials
(1)Sheet and panel-type materials described in Article 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 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.
Open OBC Div. B 9.25.5.2. in the code viewer
OBC Div. B 12.1.1.2. Application
(1)This Part applies to resource conservation and environmental integrity in the design and construction of buildings.
Open OBC Div. B 12.1.1.2. in the code viewer
OBC Div. B 12.2.1.2. Energy Efficiency Design
(1)Reserved.
(2)Except as provided in Sentence (3) and Sentence (4), the energy efficiency of all buildings shall
(a)be designed to exceed by not less than 13% the energy efficiency levels required by Sentence 12.2.1.1.(2) of O. Reg. 332/12 (Building Code) as it read on December 31, 2024, or
(b)conform to Division 1 and Division 3 or 5 of MMA Supplementary Standard SB-10, “Energy Efficiency Requirements.”
(3)Except as provided in Sentence (4), the energy efficiency of a building or part of a building of residential occupancy that is within the scope of Part 9 and is intended for occupancy on a continuing basis during the winter months shall
(a)be designed to exceed by not less than 15% the energy efficiency levels required by Sentence 12.2.1.1.(3) of O. Reg. 332/12 (Building Code) as it read on December 31, 2024, or
(b)conform to Chapters 1 and 3 of MMA Supplementary Standard SB-12, “Energy Efficiency for Housing.”
(4)This Article does not apply to
(a)a farm building,
(b)a building that does not use electrical power or fossil fuel, or
(c)a seasonal recreational building described in Section 9.37. or 9.39.
Open OBC Div. B 12.2.1.2. in the code viewer
OBC Div. B 12.3.1.3. Temperature Control in Houses and Dwelling Units
(1)Except as provided in Sentence (3) and except where space heating energy is provided by a solid fuel-burning appliance or a ground source heat pump,
(a)heating system in an individual dwelling unit shall be controlled by at least one programmable thermostatic control device located in the dwelling unit, and
(b)where a house contains a secondary suite, each dwelling unit shall be controlled by at least one programmable thermostatic control device located in the dwelling unit.
(2)The programmable thermostatic control device required in Sentence (1) shall
(a)allow the setting of different air temperatures for at least
(i)four time periods per day, and
(ii)two different day-types per week,
(b)include a manual override, and
(c)allow the setting of the air temperature to
(i)13°C or lower in heating mode, and
(ii)29°C or higher in cooling mode, where air-conditioning is provided.
(3)A manual thermostatic control device is permitted if it
(a)controls a heating or cooling system where the heating or cooling capacity is not more than 2 kW, or
(b)serves an individual room or space.
Open OBC Div. B 12.3.1.3. in the code viewer
OBC Div. B 12.3.1.4. Hot Water Piping Insulation
(1)Hot water pipes that are vertically connected to a hot water storage tank shall have heat traps on both inlet and outlet piping as close as practical to the tank, except where the tank
(a)has an integral heat trap, or
(b)serves a recirculating system.
(2)The first 2.5 m of hot water outlet piping of a hot water storage tank serving a non-recirculating system shall be insulated to provide a thermal resistance of not less than RSI 0.62.
(3)The inlet pipe of a hot water storage tank between the heat trap and the tank serving a non-recirculating system shall be insulated to provide a thermal resistance of not less than RSI 0.62.
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OBC Div. B 12.3.1.5. Residential Furnaces
(1)A furnace serving an individual dwelling unit in a house shall be equipped with a brushless direct current motor. (See Note A-12.3.1.5.(1))
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OBC Div. B 12.3.1.6. Energy Supply for Kitchen and Laundry Facilities
(1)In order to supply energy to cooking appliances and clothes dryers, every kitchen and laundry space shall be provided with
(a)an electrical outlet,
(b)a natural gas line, or
(c)a propane line.
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OBC SB-12 1.1.1.3. Compliance Options
(1)The energy efficiency of a building or part of a building of residential occupancy that is within the scope of Part 9 of Division B of the Building Code and is intended for occupancy on a continuing basis during the winter months shall comply with
(a)Subsection 3.1.1. (Prescriptive Compliance Packages) of Chapter 3,
(b)Subsection 3.1.2. (Performance Compliance) of Chapter 3, or
(c)Subsection 3.1.3. (Other Acceptable Compliance Methods) of Chapter 3.
(2)Factory-built modular homes manufactured before January 1, 2017 in accordance with the Building Code as it read on December 31, 2016 shall be deemed to be in compliance with Sentence (1).
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OBC SB-12 3.1.1.1. Energy Efficiency
(1)Except as provided in Articles 3.1.1.4. to 3.1.1.11., the building shall conform to
(a)Article 3.1.1.2. if the building is located in Zone 1 with less than 5000 heating degree days, or
(b)Article 3.1.1.3. if the building is located in Zone 2 with 5000 or more heating degree days.
(2)Except as required in Sentence (5), all walls, ceilings, floors, windows and doors that separate heated space from unheated space, the exterior air or the exterior soil shall have thermal resistance ratings conforming to this Subsection.
(3)Where specified in compliance packages in Tables 3.1.1.2.A to 3.1.1.2.C and Tables 3.1.1.3.A to 3.1.1.3.C, space heating equipment, domestic water heating equipment and heat or energy recovery ventilators shall be provided and have the efficiency rating conforming to this Subsection. (See Appendix A.)
(4)Except as required in Sentence (5), insulation shall be provided between heated and unheated spaces and between heated spaces and the exterior in accordance with this Chapter.
(5)A building envelope assembly that separates a conditioned space from an adjoining storage garage shall be treated as an assembly separating heated space from exterior, even if the storage garage is intended to be heated.
(6)Reflective surfaces of insulating materials shall not be considered in calculating the thermal resistance of building assemblies.
(7)Except as provided in Sentences (8) and 3.1.1.11.(3), where the ratio of the gross area of windows, sidelights, skylights, glazing in doors and sliding glass doors to the gross area of peripheral walls measured from grade to the top of the upper most ceiling is not more than 17%, the building shall comply with a compliance package selected from Tables 3.1.1.2.A to 3.1.1.2.C and Tables 3.1.1.3.A to 3.1.1.3.C, and Table 3.1.1.11. (See Appendix A.)
(8)Except as permitted in Sentences 3.1.1.11.(3), where the ratio of the gross area of windows, sidelights, skylights, glazing in doors and sliding glass doors to the gross area of peripheral walls measured from grade to the top of the upper most ceiling is more than 17% but not more than 22%, the building shall comply with a compliance package selected from Tables 3.1.1.2.A to 3.1.1.2.C, Tables 3.1.1.3.A to 3.1.1.3.C and Table 3.1.1.11. and the overall coefficient of heat transfer of the fenestration shall be upgraded to
(a)1.6 where 1.8 is required by the selected compliance package or permitted by Article 3.1.1.4.,
(b)1.4 where 1.6 is required by the selected compliance package or permitted by Article 3.1.1.4.,
(c)1.2 where 1.4 is required by the selected compliance package or permitted by Article 3.1.1.4., and
(d)1.0 where 1.2 is required by the selected compliance package or permitted by Article 3.1.1.4.
(See Appendix A.)
(9)Where the ratio of gross area of windows, sidelights, skylights, glazing in doors and sliding glass doors to the gross area of peripheral walls measured from grade to the top of the upper most ceiling is more than 22%, the building shall comply with Subsection 3.1.2. (See Appendix A.)
(10)Where a dwelling unit has a walkout basement, the thermal performance level of the exterior basement wall shall be not less than that required for the above grade wall for
(a)the basement wall containing the door opening, and
(b)any basement wall that has an exposed wall area above the ground level exceeding 50% of that basement wall area.
(11)For a conditioned space, the exterior building envelope or envelope that separates conditioned space from unconditioned space shall conform to the applicable values specified in Articles 3.1.1.2. and 3.1.1.3.
(12)Where an enclosed unheated space is separated from a heated space by glazing, the unheated enclosure may be considered to provide a thermal resistance of RSI 0.16.
(13)Where a compliance package in Tables 3.1.1.2.A to 3.1.1.2.C, Tables 3.1.1.3.A to 3.1.1.3.C, or Table 3.1.1.11. specifies a nominal RSI value, effective RSI value and U-Value for a component specified in Column 1 of the Table and the component conforms to one of the thermal values, the component need not conform to the other thermal values specified for the component.
(14)Insulation in the rim joist or header area where the floor assembly and wall assembly intersect shall have a thermal value not less than the thermal value of the insulation in the walls above grade.
(15)Where a compliance package in Tables 3.1.1.2.A to 3.1.1.2.C, Tables 3.1.1.3.A to 3.1.1.3.C, or Table 3.1.1.11. specifies an overall coefficient of heat transfer and an energy rating value for a fenestration component specified in Column 1 of the Table and the component conforms to one of the thermal values, the component need not conform to the other thermal value specified for the component.
(16)Ventilation systems serving dwelling units shall have a heat or energy recovery ventilator. (See Appendix A)
(17)Except as provided in Sentence (18), a building is permitted to be designed in conformance with any of the compliance packages available for the climate zone that the building is located in, if the primary space heating of the building is supplied by
(a)a wood burning appliance,
(b)an earth energy system, or
(c)an air or water source heat pump that does not use electric resistance as a back-up heat source.
(18)For the purpose of Sentence (17), the requirements in the compliance packages for space heating equipment do not apply.
(19)Heat or energy recovery ventilators specified in compliance packages in Tables 3.1.1.2.A to 3.1.1.2.C and Tables 3.1.1.3.A to 3.1.1.3.C, shall meet
(a)the requirements of Article 9.32.3.12. of Division B of the Building Code, and
(b)the minimum SRE required in this Chapter based on a test temperature of 0°C at an air flow rate equal to the principle exhaust flow but need not exceed 30 L/s.
(20)Building envelope components that enclose a common space and are exposed to exterior or unconditioned space shall conform to this Subsection.
(21)Heating, ventilating, air-conditioning and lighting systems serving common spaces need not comply with this Subsection but shall comply with the other parts of the Building Code.
(22)Drain water heat recovery units shall be installed in accordance with Article 3.1.1.12.
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OBC SB-12 3.1.1.10. Minimum Thermal Resistance of Doors
(1)Except as provided in Sentence (2) and except for doors in enclosed unheated vestibules and cold cellars, and except for glazed portions of doors, all doors that separate heated space from unheated space shall have a thermal resistance of not less than RSI 0.7 where a storm door is not provided.
(2)One exterior door system, with a single or multiple leaf door, that does not comply with Sentence (1) is permitted for each dwelling unit.
(3)All doors that separate heated space from unheated enclosed spaces shall have an insulated core and be installed with weatherstripping.
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OBC SB-12 3.1.1.12. Drain Water Heat Recovery
(1)Except as provided in Sentence (2), a drain water heat recovery unit shall be installed in each dwelling unit to receive drain water from all showers or from at least two showers where there are two or more showers in the dwelling unit. (See Appendix A.)
(2)Sentence (1) does not to apply to dwelling units in which:
(a)there are no showers; or
(b)there are no storeys or crawl spaces beneath any of the showers in the dwelling unit.
(3)Drain water heat recovery units shall conform to CSA B55.2, "Drain Water Heat Recovery Units".
(4)The minimum efficiency of a drain water heat recovery unit shall be determined in conformance with CSA B55.1, "Test Method for Measuring Efficiency and Pressure Loss of Drain Water Heat Recovery Units".
(5)The efficiency of a drain water heat recovery unit, when tested in accordance with Sentence (4), shall be not less than 42%.
(6)A drain water heat recovery unit shall be installed
(a)in an upright position that does not diverge more than 5 degrees from the vertical,
(b)in a position such that the cold water inlet connection is at the bottom of the unit,
(c)downstream of a water softener where a water softener is installed, and
(d)in a conditioned space or on the warm side of the dewpoint of the wall assembly.
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OBC Div. B 12.4.1.1. Plumbing Systems
(1)All buildings shall conform to the water efficiency requirements of Subsection 7.6.4.
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