Ontario Building Code HVAC Requirements: The 2026 Plain-English Guide to Sections 9.32, 9.33, and SB-12

If you applied for a new-home building permit in Ontario before April 2025 and you’re still working off that same paperwork, there’s a fair chance some of it doesn’t comply anymore. The Ontario Building Code changed in a big way on January 1, 2025, with a short grace period until March 31, 2025. Every new permit since then has to be to the 2024 Ontario Building Code — not the 2012 edition that the entire industry got used to over the last 13 years.

For HVAC specifically, the changes are real. House Types I, II, III, and IV are gone. Heat recovery ventilation is now effectively mandatory. The Mechanical Ventilation Design Summary is no longer optional documentation in your permit package. And the heat loss calculation that some builders quietly skipped or copy-pasted from the last house? That doesn’t fly anymore either.

This is the plain-English version of what OBC 2024 actually requires for HVAC in new residential construction. No legalese. No marketing pitch. Just what your permit package needs to contain, why each piece is there, and where homeowners and self-builders most commonly get it wrong.

One honest disclaimer before we start: the Code is a moving target. Municipalities interpret some sections slightly differently, supplementary standards get updated, and individual building departments can ask for documentation that goes beyond the strict minimum. What follows is accurate as of writing and reflects the OBC 2024 as filed under O. Reg. 163/24. Always confirm specifics with your local building department.

What changed in OBC 2024 — the short version

The 2024 Building Code came into force January 1, 2025, with a transition window until March 31, 2025 for designs already in progress. Since April 1, 2025, every new residential permit must comply with the 2024 edition. The province describes it as the largest harmonization with the National Building Code in Ontario history — roughly 1,730 technical variations removed.

For HVAC and energy compliance, the substantive changes sit in three places: Section 9.32 (Ventilation), Section 9.33 (Heating and Air Conditioning), and the supplementary standard known as SB-12 (Energy Efficiency for Housing). The official Ontario.ca page on the 2024 Building Code has the regulatory background. We’ll walk through each of the three sections that matter for HVAC below.

Section 9.32 — Ventilation (the biggest changes)

If you only read one part of OBC 2024 before talking to your designer, make it this one. Section 9.32 was reorganized from the ground up.

Under the old 2012 Code, houses were classified into ventilation Types I through IV based on fuel type and venting arrangement — whether you had a gas furnace with a chimney, a direct-vent appliance, electric heat only, and so on. Those four house types are gone. The 2024 Code does not classify houses by type at all anymore. If your designer’s permit package still references “House Type II ventilation requirements,” they’re still working from the 2012 Code and your permit will get bounced.

The new structure splits ventilation into two operating modes:

• Heating-season mechanical ventilation (Subsection 9.32.2) — how the house gets fresh air during winter, when windows stay shut and air leakage is at its annual minimum.
• Non-heating-season ventilation (Subsection 9.32.3) — how the house gets fresh air during shoulder seasons and summer, when natural ventilation can do part of the job.

Each mode has its own requirements for principal exhaust, supplemental exhaust, and make-up air. The Code also adds 15 pages of appendix notes (starting around A-9.32.1.2.(2)) showing acceptable arrangements of mechanical ventilation equipment.

The practical changes you need to know about:

• Heat or energy recovery is effectively mandatory. An HRV (heat recovery ventilator) or ERV (energy recovery ventilator) is now built into the assumed ventilation strategy for every new home. Skipping one is no longer a realistic compliance path under Section 9.32.
• A Mechanical Ventilation Design Summary (MVDS) is required in the permit package. The MVDS must follow CAN/CSA-F326, document the ventilation system design, and accompany the application. Most municipalities now require this on the cover sheet of any HVAC submittal.
• Principal exhaust at a minimum 100 CFM is required in every kitchen.
• Supplemental bathroom exhaust at a minimum 50 CFM per bathroom.
• Make-up air is now prescriptive (Subsection 9.32.3.8) when there are exhaust devices in the home that, combined, would exceed certain thresholds — or when fuel-fired appliances aren’t direct-vent or mechanically vented.

Section 9.33 — Heating and Air Conditioning

This is where the heat loss calculation requirement lives. Section 9.33 was also expanded in OBC 2024, picking up residential duct system requirements that used to sit in Subsection 6.2.4 of the old Code.

The core requirement most homeowners don’t realize is in Sentence 9.33.2.2: the heating system in a new home must be sized using a calculated heating load, not a contractor’s gut feel. The recognized standard for that calculation is CSA F280-12 — the Canadian engineering standard that uses your actual wall assemblies, actual window specs, actual glazing area, and the design temperature for your specific Ontario municipality.

“We sized it like the last house we built” is not a compliant answer. Neither is “we used an online calculator.” The F280-12 calculation must be stamped by a BCIN-registered designer and submitted with the permit application. For more on how the heat loss calc works and what your designer should be producing, see our companion guide to the Ontario heat loss calculator.

Section 9.33 also covers:

• Duct sizing and layout for forced-air systems (now per HRAI calculation methodology)
• Combustion air for fuel-fired appliances
• Clearances around equipment
• Venting requirements for natural-draft, induced-draft, and direct-vent appliances
• Hydronic system requirements where applicable (boilers, radiant floors)

Three different reports — don’t mix them up

Homeowners constantly confuse the three energy-related documents that show up around a new home build. Here’s how they differ:

We covered the EnerGuide side in detail in our guide to Ontario home energy audits. The other three live inside the building permit world.

SB-12 — The energy efficiency side

Supplementary Standard SB-12 is the document that translates OBC Part 12 (Resource Conservation and Environmental Integrity) into actual prescriptive requirements for new housing. It sits beside the main Code as a supplementary standard, and it applies to every new residential building within the scope of Part 9.

SB-12 gives builders three compliance paths:

Ontario is split into two climate zones for SB-12 purposes. Zone 1 covers Southern Ontario — Toronto, Hamilton, London, Ottawa, Niagara, and most of the populated south. Zone 2 covers Northern Ontario — areas with significantly higher heating degree days, which means higher minimum R-values and tighter mechanical requirements.

For airtightness, SB-12’s performance path references targets of 2.5 air changes per hour at 50 pascals (ACH50) for detached homes and 3.0 ACH50 for attached homes — with airtightness credit available if you beat those numbers and test as-built. These are not blanket requirements under the prescriptive path, but they become real numbers when you submit blower-door results for any project pursuing the airtightness credit.

What your permit package must contain for HVAC compliance

Pull these together before you submit, and your permit review goes faster:

1. A CSA F280-12 heat loss calculation, room-by-room, stamped by a BCIN-registered HVAC designer, using the design temperature for your municipality.
2. A Mechanical Ventilation Design Summary (MVDS) per CAN/CSA-F326, documenting principal and supplemental exhaust, fresh air intake, HRV/ERV sizing and capacity, and ductwork.
3. Mechanical drawings showing equipment placement, duct routing, intake and exhaust locations, and clearances.
4. An Energy Efficiency Design Summary (EEDS) form referencing the SB-12 compliance path you’re using (prescriptive, performance, or other), with the specific table and package identified.
5. Heat pump or furnace specifications matched to the calculated load — not oversized "to be safe." Oversizing causes short-cycling and is increasingly flagged by reviewers.
6. For cold-climate heat pumps, manufacturer documentation showing capacity at the local design temperature (often -22°C to -30°C in Southern Ontario), and balance-point calculations if a hybrid system is proposed.
7. A BCIN registration number for the designer, listed on every drawing and form. No BCIN, no acceptable design submission.

Common mistakes that get permits rejected

What inspectors actually check

One more thing — ICF and high-performance builds

If you’re building with insulated concrete forms, you tend to crush SB-12’s prescriptive requirements without trying. ICF walls deliver continuous insulation, near-zero thermal bridging, and air tightness numbers that make blower-door tests look easy. That doesn’t exempt you from the paperwork — you still need the F280-12 heat loss calc, the MVDS, the EEDS form, and the BCIN designer — but it does mean your envelope side is sorted before you even start. The contractor side of ICF work is covered at ICFpro.ca for builders and subtrades, and our ICFpro insights archive goes deeper on the building science.

If you’re at the planning stage of a new home and trying to wrap your head around the whole permit-to-occupancy sequence, our 10 steps to building a new home in Ontario walks through it from the homeowner’s side. And if you’re combining new construction with energy upgrades and trying to navigate rebates at the same time, the Home Renovation Savings Program guide covers the active 2026 programs.

For the full text of the HVAC-specific OBC 2024 changes, the Heating, Refrigeration and Air Conditioning Institute (HRAI) maintains a detailed comparison document available through the HCRA’s OBC HVAC update page — worth bookmarking if you’re going to be inside this code for more than one project.

Frequently asked questions

If you’re at the planning stage of a new home in Ontario, the cheapest moment to get the HVAC compliance right is now — before drawings get finalized and certainly before crews show up. Get a BCIN designer on the F280 and the MVDS, confirm your SB-12 compliance path early, and don’t accept a permit package built from a 2012-Code template. — Harvey, on behalf of the crew.