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Decoding Ontario's Building Code Ventilation Requirements: What They Are and Who They Apply To

Decoding Ontario's Building Code Ventilation Requirements: What They Are and Who They Apply To

Credit: Drew Beamer


Adhering to and understanding code requirements can become overwhelming, especially when dealing with large or multiple projects. Protect your building occupants and ensure a quick inspections process with our short guide to decoding the Ontario building code ventilation requirements.

Recently, Ontario updated its series of ventilation code requirements to increase the energy performance of a building by 15 percent. The updates center around heat recovery on ventilation systems with incentives for making buildings more airtight.

While much of the Ontario Building Code 2020 (OBC) Section 9 remains the same, a heat-recovery ventilator (HRV) or an energy-recovery ventilator (ERV) will be mandatory for all commercial and residential buildings.

The Main Code Requirements for Ventilation

Two main areas discuss ventilation and must be followed to pass inspection, Section 9 and the updated SB12 of the OBC. SB12 is pretty straightforward and handles the energy performance requirements of ventilation systems. Section 9, on the other hand, has over 40 subsections of building code requirements, but only a handful address ventilation.


The Supplementary Standard SB12, the Energy Efficiency for Housing, updated in 2016, is a prescriptive requirement to achieve an acceptable air leakage rating of 80 or more by the NRCan "EnerGuide for New Houses: Administrative and Technical Procedures."

There are three compliance options:

  1. Choose a prescriptive compliance package.
  2. Create a design that complies with the performance compliance method.
  3. Create a design that adheres to Energy Star requirements.


Learn about AirFixture’s underfloor HVAC systems:


Section 9 of the OBC

Section 9 of the OBC addresses code requirements for several critical areas to ensure proper ventilation of a commercial building or residential dwelling. There are two sections to be especially mindful of:

Section Vent Requirements
  • (1) An unobstructed vent area cannot be less than 1/300 of the insulated ceiling area except as provided in Sentence (2)
  • (2) If the roof slope is less than 1 in 6 or for roofs constructed with joists, the unobstructed vent cannot be less than 1/150 of the insulated ceiling area.
  • (3) Required vents can be roof-type, eave-type, gable-end-type, or a combination of the three with distribution:
    • (a) uniformly on opposite sides of the building
    • (b) not less than 25% of the required openings located at the top of the space
    • (c) not less than 25% of the required openings located at the bottom of the space
  • Roof joist spaces must be interconnected by installing purlins greater or equal to 38mm by 38mm on top of the roof joists except as provided in Sentence (2)
  • Vents must comply with the CAN3-A93-M "Natural Airflow Ventilators for Buildings"
Section Ventilation of Rooms and Spaces
  • (1) Rooms or spaces in commercial or residential buildings must be ventilated by natural means per Subsection except as permitted in Sentence (2)
  • (2) The requirement for natural ventilation can be met through mechanical ventilation systems
  • (3) Ontario building code air changes per hour - If a room does not have adequate natural ventilation as stated in Sentence (1), mechanical ventilation must be provided at a rate of ½ air change per hour if mechanically cooled in the summer, or 1 air change per hour if not

Other OBC Section 9 subsections that should be considered for proper safety and compliance:

  • - Mechanical Ventilation for Residential Occupants
  • - Natural Ventilation Area
  • - Required Mechanical Ventilation
  • - Total Ventilation Capacity


Ontario building code ventilation requirements

Credit: Vadim Babenko


Consequences of Not Meeting the Updated Requirements

Not meeting current building requirements can affect homeowners, property managers, builders, and contractors alike. There could be delays in inspection approvals, loss of money for property managers wanting to move someone into an area, or delays in closing a project for a contractor.

Understanding building codes may be confusing, but they’re designed to ensure the safety and wellbeing of occupants and those working on a project. After all, no one wants to accidentally breathe in pollutants because the ventilation systems weren't installed properly.


Ensure Complete Compliance with AirFixture

Building requirements can be a struggle to learn and decode to the point where you feel confident enough to proceed with construction. Working with an experienced and licensed contractor can cut down on the headache of trying to learn the Ontario building code ductwork and ventilation requirements.

For decades AirFixture has been providing commercial-grade, state-of-the-art ventilation systems that meet industry standards, local code requirements, and improve energy efficiency. Contact AirFixture today to learn more about the advantages of hiring a professional to handle your ventilation needs.

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