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Insulation Requirements in the Ontario Building Code

Insulation R-values for new Ontario houses under the 2024 Building Code: SB-12 packages, Zone 1 and 2, attic and wall values, nominal vs effective.
attic ceiling in most Zone 1 high-efficiency packages (about R60)
RSI 10.56
attic ceiling in most Zone 1 high-efficiency packages (about R60)
above-grade wall cavity, Zone 1 package A1 (about R22)
RSI 3.87
above-grade wall cavity, Zone 1 package A1 (about R22)
heating degree days that start Zone 2
5,000
heating degree days that start Zone 2
minimum over attic hatches and at the eaves
RSI 3.52
minimum over attic hatches and at the eaves

Last updated

For a new house under the 2024 Ontario Building Code, insulation values are not in Part 9: Part 12 sends houses to Supplementary Standard SB-12, and its most common Zone 1 packages for high-efficiency furnaces call for about RSI 10.56 (R60) in the attic and RSI 3.87 (R22) or more in above-grade walls (OBC Div. B 12.2.1.2.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…, SB-12 Table 3.1.1.2.AOBC SB-12 Table 3.1.1.2.A. (SI) — Zone 1 — Compliance Packages for Space Heating Equipment with AFUE ≥ 92%Table 3.1.1.2.A. (SI) — Zone 1 — Compliance Packages for Space Heating Equipment with AFUE ≥ 92% Forming Part of Sentence 3.1.1.2.(1) Component | Thermal Values[8] | Compliance Package A1 | Compliance Package A2 | Compliance Package A3 | Compliance Package A4 | Compliance Package A5 | Compliance Package A6 Ceiling…). The exact numbers depend on the compliance package you choose, which is set by your climate zone and your heating equipment.

This page explains how the system works and how to read a package. Basement walls and slabs have their own page: see basement insulation and the Ontario Building Code. Your building department has the final say on what your permit drawings must show.

Insulation rules at a glance

Question Short answer Where to look
Where are the R-values for houses? SB-12, through Part 12 12.2.1.2.(3)
Which compliance routes exist? prescriptive package, performance path, or Energy Star / R-2000 SB-12 1.1.1.3.
Zone 1 or Zone 2? under 5,000 heating degree days is Zone 1; 5,000 or more is Zone 2 SB-12 3.1.1.1.(1)
Which table? by zone and heating: 92% AFUE or more, 84% to under 92%, or electric SB-12 3.1.1.2. and 3.1.1.3.
Attic ceiling, example RSI 10.56 nominal in package A1, Zone 1, 92% AFUE or more SB-12 Table 3.1.1.2.A
Above-grade walls, example RSI 3.87 nominal in the same package SB-12 Table 3.1.1.2.A
Over attic hatches and at the eaves may be reduced, but not below RSI 3.52 SB-12 3.1.1.8.
Rim joists at least the above-grade wall value SB-12 3.1.1.1.(14)
Wall to an attached garage treated as an exterior wall SB-12 3.1.1.1.(5)

These rows are our own summary. The packages also set window, furnace, HRV and water heater values, so read the whole column for your package.

How the energy rules fit together

Part 12 gives a Part 9 house that is lived in through the winter two choices: be designed to beat the energy efficiency levels of the 2012 code by at least 15%, or follow Chapters 1 and 3 of SB-12, "Energy Efficiency for Housing" (12.2.1.2.(3)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…). Farm buildings, buildings that use no electricity or fossil fuel, and the seasonal recreational buildings of Sections 9.37 and 9.39 are exempt from that article.

SB-12 itself offers three routes (SB-12 1.1.1.3.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…):

  1. Prescriptive compliance packages (Subsection 3.1.1.): pick one package and meet every line in it.
  2. Performance compliance (Subsection 3.1.2.): model the proposed house and show its simulated annual energy use is no greater than a reference house built to a package. The envelope can be weaker than the package, but by no more than 25% (SB-12 3.1.2.1.OBC SB-12 3.1.2.1. Required Performance Level(1) The performance level shall be measured based on the simulated annual energy use of the building. (2) For the purpose of this Subsection, reference building means a building that is identical to the proposed building, except that it is designed to meet the requirements and performance level of an applicable…).
  3. Other acceptable methods (Subsection 3.1.3.): a house that achieves the Energy Star for New Homes Standard Version 12.6 performance level, or meets the 2012 R-2000 Standard, is deemed to comply (SB-12 3.1.3.1.OBC SB-12 3.1.3.1. Other Acceptable Compliance Methods(1) A building shall be deemed to be in compliance with the requirements of Subsection 3.1.1. (a) Provided that the same performance level is achieved through the technical requirements of NRCan, "Energy Star for New Homes Standard Version 12.6." or, (b) The building meets the NRCan, "2012 R-2000 Standard".).

Part 9 still controls how insulation is installed: uniform coverage over the whole area, full width and length between framing, and at least one face against a low air permeance material unless the insulation itself is the air barrier (OBC Div. B 9.25.2.3.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…).

Step 1: find your zone

SB-12 splits Ontario by heating degree days: Zone 1 has less than 5,000, Zone 2 has 5,000 or more (SB-12 3.1.1.1.(1)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…). The degree days for each town are in the "Degree Days Below 18 C" column of SB-1 Table 2OBC SB-1 Table 2: Climatic Design DataTable 2: Climatic Design Data Location | Elevation, m | Design Temperature — January — 2.5%, °C | Design Temperature — January — 1%, °C | Design Temperature — July 2.5% — Dry, °C | Design Temperature — July 2.5% — Wet, °C | Degree Days Below 18°C | 15 Min Rain, mm | One Day Rain, 1/50, mm | Annual Rain, mm | Moisture….

Location in SB-1 Heating degree days SB-12 zone
Toronto (City Hall) 3,520 Zone 1
Ottawa (City Hall) 4,440 Zone 1
Sault Ste. Marie 4,960 Zone 1, just under the line
Sudbury 5,180 Zone 2
Thunder Bay 5,650 Zone 2

Step 2: pick the table by heating equipment

Each zone has three tables. In Zone 1, Table 3.1.1.2.A is for space heating equipment of 92% AFUE or more, Table 3.1.1.2.B for 84% to under 92%, and Table 3.1.1.2.C for electric space heating (SB-12 3.1.1.2.OBC SB-12 3.1.1.2. Energy Efficiency for Buildings Located in Zone 1(1) Except as provided in Sentences (2) to (5) and (7), the minimum thermal performance of building envelope assemblies and equipment shall conform to Table 3.1.1.2.A. (2) Except for solid fuel-burning space heating equipment and except as provided in Sentence (5), where the space heating equipment efficiency is 84%…). Zone 2 mirrors this with Tables 3.1.1.3.A to C (SB-12 3.1.1.3.OBC SB-12 3.1.1.3. Energy Efficiency for Buildings Located in Zone 2(1) Except as provided in Sentences (2) to (5) and (7), the minimum thermal performance of building envelope assemblies and equipment shall conform to Table 3.1.1.3.A. (2) Except for solid fuel-burning space heating equipment and except as provided in Sentence (5), where the space heating equipment efficiency is 84%…). Where the heating equipment cannot meet any package, the house must use the performance path. A house heated mainly by a wood burning appliance, an earth energy system or a heat pump without electric resistance back-up may use any package for its zone (SB-12 3.1.1.1.(17)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…).

Step 3: read one package column

Each table has packages side by side (A1, A2 and so on). Choose one column and meet every row in it. As an example, in Zone 1 package A1 for 92% AFUE or more, the attic ceiling needs nominal RSI 10.56 and above-grade walls need nominal RSI 3.87, with the furnace, HRV, window and water heater values in the same column. Other packages in the same table trade a smaller attic value (RSI 8.80) or added continuous insulation on the walls against better windows or equipment.

Two more checks before you settle on a package:

  • Window to wall ratio. Packages apply as written up to 17% glazing. From 17% to 22%, the windows must be upgraded to a lower U-value, and above 22% the house must use the performance path (SB-12 3.1.1.1.(7) to (9)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…).
  • Ventilation. Ventilation systems serving dwelling units need a heat or energy recovery ventilator (SB-12 3.1.1.1.(16)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…).

The SB-12 worked method takes you through a full package lookup.

Nominal vs effective RSI

The packages list two kinds of value. Nominal RSI is the label rating of the insulation alone. Effective RSI is the resistance of the whole assembly, from the inside air film to the outside, including studs, sheathing and drywall (SB-12 1.3.1.2.OBC SB-12 1.3.1.2. Defined Terms(1) Each of the words and terms in italics in this Supplementary Standard has the same meaning as in subsection 1(1) of the Building Code Act, 1992 or Sentence 1.4.1.2.(1) of Division A of the Building Code. (2) In this Supplementary Standard, common space means all spaces required to be conditioned spaces in…). Framing conducts heat, so effective values are lower in framed walls.

SB-12's own appendix examples show the gap. A 38 x 140 mm stud wall at 406 mm o.c. with RSI 3.87 batts and RSI 0.88 exterior foam works out to an effective RSI of about 3.77 (SB-12 wall exampleOBC SB-12 Above Grade Wall - RSI Nominal 3.87 + 0.88 ci (vinyl)Above Grade Wall - RSI Nominal 3.87 + 0.88 ci (vinyl) Details | Effective RSI Air film exterior | 0.03 Exterior Finish* - Siding - vinyl, hollow-backed | 0.11 RSI 0.88 (R5) XPS sheathing | 0.88 Stud dimensional lumber – 38 mm x 140 mm (2" x 6") 406 mm (16") on-centre RSI 3.87 (R22) nominal cavity fill between studs |…), and an attic with nominal RSI 8.80 comes to an effective 8.67 (SB-12 attic exampleOBC SB-12 Ceiling with Attic Space - RSI Nominal 8.80Ceiling with Attic Space - RSI Nominal 8.80 Details | Effective RSI Roof sheathing (above vented air space, therefore excluded from calculation) | 0 Vented roof air space | 0.03 RSI 6.69 (R38) nominal of blown in cellulose | 6.69 Roof truss bottom chord dimensional lumber - 38 mm x 89 mm (2" x 4"), 610 mm (24")…). Where a package lists nominal, effective and U-values for a component, meeting any one of them is enough (SB-12 3.1.1.1.(13)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…). Reflective foil faces do not count toward thermal resistance (SB-12 3.1.1.1.(6)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…).

To convert RSI to the imperial R-value used on product labels, multiply by about 5.678: RSI 3.87 is about R22, RSI 8.80 about R50 and RSI 10.56 about R60.

Attic details

The ceiling value can be reduced directly above an access hatch and near the eaves where the roof slope and ventilation clearances leave no room, but never below RSI 3.52 at the hatch and over the inner face of the exterior walls (SB-12 3.1.1.8.OBC SB-12 3.1.1.8. Thermal Resistance Values for Roof Access Hatches and Eaves(1) Except as provided in Sentence (2), the thermal resistance values for insulation required by Articles 3.1.1.2., 3.1.1.3. and 3.1.1.11. for exposed ceilings with attic spaces are permitted to be reduced (a) directly above access hatches, and (b) near eaves to the extent made necessary by the roof slope and required…). Attic insulation must also leave the roof vents clear: Part 9 requires a vented space between the insulation and the roof sheathing (OBC Div. B 9.19.1.1.OBC Div. B 9.19.1.1. Required Venting(1) Except where it can be shown to be unnecessary, where insulation is installed between a ceiling and the underside of the roof sheathing, a space shall be provided between the insulation and the sheathing, and vents shall be installed to permit the movement of air from the space to the exterior. (See Note…) and says ceiling insulation must not restrict the air flow through the vents (9.19.1.3.OBC Div. B 9.19.1.3. Clearances(1) Except as provided in Sentence (2), where venting is provided to a roof joist space, not less than 63 mm of space shall be provided between the top of the insulation and the underside of the roof sheathing. (2) Where venting is provided at the junction of sloped roofs and exterior walls and where preformed baffles…).

Common mistakes

  1. Looking for R-values in Section 9.36. It is reserved in Ontario; the values are in SB-12.
  2. Mixing packages, such as the attic from one column and the walls from another.
  3. Ignoring the furnace or HRV lines. A package is the whole column, not just insulation.
  4. Picking the wrong zone for towns near 5,000 degree days.
  5. Treating the garage wall as interior. SB-12 treats it as exterior even if the garage is heated.
  6. Forgetting the rim joist, which needs at least the above-grade wall value.

How to look it up yourself

In Volume 1, Division B, go to Part 12, Article 12.2.1.2. In Volume 2, open SB-12, Chapter 3. Search terms that appear in the text:

  • "Compliance Packages" (the table titles)
  • "heating degree days" (the zone rule in 3.1.1.1.)
  • "Minimum Nominal RSI" and "Minimum Effective RSI" (table rows)
  • "access hatches" (3.1.1.8.)
  • "Other Acceptable Compliance Methods" (Energy Star and R-2000)

BCIN exam angle

SB-12 package questions are a known stumbling block on the House exam and appear on HVAC - House and Small Buildings: find the zone, choose the table by furnace efficiency, then read one column. Study the House energy efficiency chapter, the HVAC - House Part 12 and SB-12 chapter or the Small Buildings energy chapter. Browse SB-12 in the code viewer, work through the SB-12 method, and try the free quiz on the House exam page.

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

© King's Printer for Ontario, 2024. Reproduced with permission.

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Frequently asked questions

What R-value is required in an attic in Ontario?
It depends on the SB-12 compliance package chosen for the house. In the Zone 1 packages for high-efficiency furnaces (Table 3.1.1.2.A), a ceiling with an attic space needs nominal RSI 10.56 (about R60) in most packages and RSI 8.80 (about R50) in the others. The insulation can be reduced over the access hatch and near the eaves, but not below RSI 3.52 (about R20) (SB-12, Article 3.1.1.8.).
What R-value do exterior walls need in Ontario?
Again it depends on the package. In Zone 1 package A1 for furnaces of 92% AFUE or more, above-grade walls need nominal RSI 3.87 (about R22) in the cavity. Other packages call for cavity insulation plus continuous insulation, such as RSI 3.87 + 0.88 ci (about R22 + R5 ci).
What is Zone 1 and Zone 2 in SB-12?
Zone 1 is a location with less than 5,000 heating degree days and Zone 2 is 5,000 or more (SB-12, Sentence 3.1.1.1.(1)). Heating degree days for each town are in SB-1, Table 2. Toronto and Ottawa are in Zone 1; Sudbury and Thunder Bay are in Zone 2.
What is the difference between nominal and effective RSI?
Nominal RSI is the rating of the insulation product alone. Effective RSI is the thermal resistance of the whole assembly, including framing, sheathing, drywall and air films, and is lower where studs or joists bridge the insulation. SB-12 packages list both, and a component meeting either value complies (SB-12, Sentence 3.1.1.1.(13)).
Do I have to follow the SB-12 packages?
No. A house can meet SB-12 by a prescriptive package, by the performance path (energy modelling against a reference house), or by building to Energy Star for New Homes 12.6 or the 2012 R-2000 Standard (SB-12, Article 1.1.1.3. and Subsection 3.1.3.). Part 12 also allows a design that beats the 2012 code's energy levels by at least 15%.