WEB EXCLUSIVE: The Updated Ontario Building Code

The update to the 2006 Ontario Building Code, which went into effect in January 2012, is the most progressive code-required energy standard in North America. There are some significant changes to the code which will likely significantly reduce the number of glass-walled towers being constructed in Ontario cities—and not a moment too soon say energy and design professionals.

What’s Changed in the Code?

The updated OBC generally follows the building standard outlined in ASHRAE 90.1-2010 combined with the green building ASHRAE 189-2009 envelope requirements. In terms of building envelopes, ASHRAE 189-2009 actually encourages the design of green buildings rather than just the “bare minimum” of energy efficiency and occupant comfort.

There are two ways to meet the updated OBC: the performance path and the prescriptive path. The performance path requires that a building be designed to achieve one of following:

  • 25% annual energy savings relative to the Model National Energy Code (this is essentially the prerequisite energy requirement for LEED).
  • 5% annual energy cost savings relative to ASHRAE 90.1-2010 (without the OBC envelope revisions)
  • Lower annual energy cost relative to the OBC prescriptive code of ASHRAE 90.1-2010 with ASHRAE 189-2009 envelope revisions

This would need to be demonstrated through an energy model that indicates what building features are improvements over the reference buildings (i.e., daylighting sensors, triple glazed windows, ultra-high-efficiency heating plants).

The prescriptive path will have some “real eye openers” for many design teams:

  • no more than 40% glazing
  • many common wall constructions, such as z girts and spandrel panels, will have challenges meeting the required insulation values
  • very high performance double glazed fenestration systems, and sometimes even triple glazed windows are required
  • heat recovery ventilation (whereby exhaust heat is used to preheat incoming fresh air) required in more building types

A Code Comparison

Every state and province has its own building code, and some are more progressive than others when it comes to promoting energy efficiency. Ontario’s is the most progressive as it represents a significant improvement over the codes in other provinces and in the US, which typically require the earlier incarnations of ASHRAE 90.1 (typically 2004 or 2007). ASHRAE 90.1-2010 (now required in Ontario) represents a significant increase in energy performance. And the province went even further by revising that standard to include the ASHRAE 189-2009 envelope performance.

Here are a few province and state comparisons:


Version of ASHRAE Required:

  • All new buildings must comply with ASHRAE 90.1-2010

Further Requirements:

  • Envelope performance must comply with ASHRAE 189-2009 (encourages green buildings rather than “bare minimum”), including a window-to-wall ratio of no more than 40%

British Columbia

Version of ASHRAE Required:

  • All new buildings must comply with ASHRAE 90.1-2004.

Further Requirements:

  • City of Vancouver enforces ASHRAE 90.1-2007;
  • Energy Efficiency Act requires all building window performance calculations to be performed by a simulator accredited by agencies such as the National Fenestration Rating Council (NRFC) or a professional engineer.


Version of ASHRAE Required:

  • Title 24 which has many similarities to ASHRAE 90.1-2007

Further Requirements:

  • Window-to-wall ratio must be 40% or lower
  • Must use highly reflective roofing
  • CO2-controlled ventilation required for all variably occupied rooms (i.e., meeting roofs, gyms, lunch rooms)
  • Occupancy sensors required offices less than 250 ft², multipurpose rooms of less than 1,000 ft², and classrooms and conference rooms

What the Updated OBC Means for Designers and Code Officials

There are several potential challenges in enacting the new building code for officials and design teams:

  • A typical new glass-walled tower has 70% window-to-wall ratio, while a punched window design often achieves 30-40%. Designers will say goodbye to many Toronto glass box tower designs, or take the energy modeling performance paths where mechanical/electrical improvements can be shown to compensate for the envelope performance.
  • Although in the past year code officials have begun asking for more documentation to prove new buildings will meet existing code requirements, the current code is not well enforced. Will officials enforce the new, more stringent building code?
  • Even if only half of new Ontario buildings choose the performance path, there will likely be a shortage of good energy modellers to help design teams prove their building is designed to achieve 25% (relative to MNECB) energy savings. Bringing an energy efficiency engineer onto projects as early as possible (before building massing) to provide design facilitation and suggest innovative, yet proven and low-cost technologies and design solutions will be increasingly critical.

Thus, to meet these more stringent building requirements, designers will have to consider new ways of improving envelope and window performance, such as

  • Using punched wall designs that make it easier to achieve window-to-wall ratios of 30-40% (vision area/total area)
  • For curtainwalls, more insulation can be placed to the interior of the spandrel panels
  • Use fibreglass rather than aluminium window frames
  • Use triple-glazed windows or curtainwalls with low-e coatings and argon fills


Despite these challenges, the 2012 OBC is a significant step in the right direction for the province and a benchmark for other provinces and states looking to make a significant impact in the area of energy efficiency.


Steve   Kemp, P.Eng, is head of the Energy Performance Group for Enermodal   Engineering, Canada’s largest green building consulting firm and a member of   MMM Group Limited. He is also Chair of the Canada Green Building Council’s   Energy & Engineering Advisory Group and president of the Canadian Chapter   of the International Building Performance Simulation Association.

 As a developer of engineering   software, he is responsible for many simulation tools including RETscreen,   EFAST and FRAMEplus online. His work also includes green building design   facilitation, renewable energy technology studies and daylighting design   analysis. Steve has been the primary energy modeller on over dozens of   projects using EE4 and EQUEST for building code compliance, LEED   certification, and efficiency incentive purposes.

You might also like