As of Jan 1st, 2012, the proposed construction of all other buildings not within the scope of Part 9 must conform to the enhanced energy efficiency requirements of the Ontario Building Code as prescribed by Supplementary Standard SB-10. These new requirements are making Ontario one of the most stringent building codes for energy efficiency in North America.

The energy efficiency requirements can be met through a prescriptive or performance compliance path.

  • The prescriptive path requires the fenestration-to-wall ratio be at most 40%, and thus may not be an option for many modern window-wall or curtain-wall facade constructions.
  • The performance path requires a whole building energy model to demonstrate compliance using approved software.

Prescriptive Path:

  • Conform to ASHRAE 90.1-2010 as modified by SB-10 Division 3 Chapter 2

Compliance Path:

  • Meet ASHRAE 90.1-2010 as modified by SB-10 Division 3 Chapter 2 (Enforces ASHRAE 90.1 2010 as minimum energy code for OBC)
  • Exceed ASHRAE 90.1-2010 by at least 5%
  • NCEB 2011 25 percent improvement in energy efficiency over the previous model energy code (MNECB)

The new Code is more consistent with the model national codes, for building and plumbing. Certain administrative and enforcement rules have also been updated.

The new Building Code have come into force on January 1, 2014, although some energy efficiency provisions come into effect on the first of January in 2015 and 2017, and certain changes related to on-site sewage systems will take effect on December 31, 2016.

 

Which to choose – ASHRAE 90.1-2010 or NECB 2011?

NECB 2011 (National Energy Code for Buildings, 2011) was developed by the National Research Council of Canada and volunteers to provides minimum requirements for the design and construction of energy-efficient buildings and covers the building envelope, systems and equipment for heating, ventilating and air-conditioning, service water heating, lighting, and the provision of electrical power systems and motors. It applies to new buildings and additions. It does not apply to farm buildings nor to housing and smaller buildings covered in Part 9 of the National Building Code of Canada (NBC)

ASHRAE 90.1 (“ANSI/ASHRAE/IES Standard 90.1-2010 – Energy Standard for Buildings Except Low-Rise Residential Buildings”) is published by ASHRAE, the international association focused on advancing building systems, energy efficiency, indoor air quality, refrigeration and sustainability. Written by a large group of members worldwide, ASHRAE 90.1-2010 is complex with specific requirements and exceptions for various applications. The goal of this standard was to cover the full range of construction approaches.

In both compliance paths the building performance requirements are defined by the climate zone, and in one location the requirements in one standard might be more stringent than in the other
Space classifications

The NECB 2011 does not define a semi-heated space (warehouses, factories etc.). In ASHRAE 90.1 a semi-heated space is defined and has reduced requirements resulting in lower construction costs. While the NECB U-value requirements may be avoided using an energy simulation of the envelope, such an approach adds complexity and cost and would fall under the discretion of the authority having jurisdiction.

Although the structure of the compliance paths is similar, ASHRAE 90.1 contains a number of mandatory provisions that must be followed regardless of the path chosen. In the NECB, nearly all requirements are prescriptive and don’t need to be followed, but if followed are like a checklist to compliance. Alternatively, if it can be shown that equivalent performance can be met in other ways, the building is deemed to comply. While ASHRAE 90.1 mandatory requirements are typically good design practice, there can be some challenges in meeting them in specific applications. A good example of this is the mandatory requirement in many applications for vestibules in new construction.

Energy cost vs. energy use

The most significant difference between the compliance paths is the baseline of net energy cost versus net energy use. ASHRAE 90.1 is based on an energy cost basis. The NECB was written to reduce energy consumption and therefore does not look at cost but rather the total energy used. This difference impacts a large number of factors. The most direct is that ASHRAE 90.1 has various U value requirements for different construction types to balance the increase in construction costs for the increased insulation, so a wood wall would have a higher insulation requirement than a mass wall. The NECB looks at building envelope performance, so only the calculated U Value is considered in compliance and has the same requirement for all construction types. The construction type needs to be reviewed when selecting the compliance path as some assemblies may be costly to insulate to the required values.

Both paths are similar in that you can use area weighted averages to show compliance for differing assemblies and they allow for some form of trade-off on the envelope. However, in the NECB you can only trade similar planes; if you want to trade off dissimilar planes you will require an energy simulation of the envelope. In ASHRAE 90.1 envelope trade-off can be done with calculations or using a program. The NECB also allows for trade-off options in all components of the building, whereas ASHRAE does not have trade-off paths for all building system components.

Due to these and a number of factors; when deciding which standard is the more practical, the answer is simple — it’s complicated! The decision therefore needs to be discussed early in the design process

ASHRAE 90.1 2010 and NECB 2011 Cross Canada Comparison

For the high rise office and high rise MURB building types, the NECB savings compared to ASHRAE are similar for Toronto, Montreal, Winnipeg, Calgary, Regina, and Saint John. The overall energy savings for these locations range from a low of 9.1% to a high of 13.6%. The majority of the overall energy savings results from a reduction in heating energy use. The NECB has significantly more stringent envelope requirements, and prescribes modulating boilers compared to single stage boilers prescribed in ASHRAE. This results in heating energy savings between 20% and 30% depending on the location. For the Halifax and Vancouver locations the overall energy use tends to be lower. Halifax and Vancouver show lower savings because they are milder climates, resulting in less potential for heating savings associated with the improved envelope and modulating boilers prescribed by NECB. Also, colder climates have larger heating savings, because the NECB prescribes a reduced maximum percentage glazing as a function of heating degree days (see Table 3), compared to ASHRAE which is capped at 40% for all locations.

What about Toronto?

Toronto has now the more restrictive building code of North America.  On top of SB-10,  achieving the TGS contributes towards LEED certification. The Toronto LEED Supplement summarizes the similarities and differences between the Toronto Green Standard and LEED Canada NC 2009 rating system and notes documentation accepted by the City of Toronto.

For the other Canadian ressources, see NECCB 2011

SOURCES:

  • Building Code Act, 1992

http://www.e-laws.gov.on.ca/html/statutes/english/elaws_statutes_92b23_e.htm

» http://www.e-laws.gov.on.ca/html/regs/english/elaws_regs_120332_e.htm

ONTARIO REGULATION 191/14 made under the BUILDING CODE ACT, 1992

 

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