Important Changes to Section 9.36. of the NBC 2020: Energy Efficiency
Zaineb Al-Faesly, Technical Advisor, Codes Canada
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Video transcript
Introduction
Hi, my name is Zaineb Al-Faesly and I am a Technical Advisor supporting the Canadian Board for Harmonized Construction Codes – also referred to as the CBHCC.
This committee is the federal-provincial-territorial body responsible for developing and maintaining the National Model Codes in Canada.
I’m a member of the Codes Canada team at the National Research Council of Canada.
Codes Canada acts as the secretariat to the CBHCC, providing administrative, technical and policy support, including publishing the National Model Codes.
To learn more about code changes and provisions in the National Model Codes, or about Canada’s national model code development system, please visit the CBHCC’s website.
This presentation is part of a video series led by the CBHCC on the key technical changes incorporated in the 2020 editions of the National Model Codes.
Topics
This presentation will focus on important changes to energy efficiency in Section 9.36. of Division B of the National Building Code of Canada 2020, and will address the building envelope, HVAC and service water heating, and performance compliance.
Section 9.36. contains requirements to minimize excessive use of energy in Part 9 houses and small buildings as a result of the:
- design and construction of the building envelope
- systems and equipment used for heating, ventilating, air-conditioning and service water heating.
Airtightness measurement
The 2015 edition of Section 9.36. lacked necessary details and procedures to enable determination of airtightness of the building envelope that may be needed for energy modeling, or to demonstrate energy performance compliance with the prescriptive path, such as receiving credits for airtightness testing.
To remedy the situation, new requirements on airtightness testing are included, which are optional in all the compliance paths.
They:
- provide guidance and reduce the need for interpretation,
- introduce a new standardized testing standard to reflect current practice, and
- offer flexibility by providing the air leakage rates in various metrics.
Thermal resistance of 9.5 mm air cavity
In walls, capillary breaks less than 13 mm were permitted in the NBC 2015, but no thermal resistance values for air cavities of less than 13 mm were provided. As these capillary breaks provide a measurable benefit to the effective thermal resistance of the wall assembly, builders should benefit from their installation and not need to add additional insulating materials to compensate.
Thermal resistance values for 9.5 mm air cavities, which are used as required capillary breaks in certain locations, are added to the 2020 edition.
Engineering analysis has demonstrated that a drained and vented 9.5 mm capillary break does provide a measurable benefit to the effective RSI of a wall assembly and should be included in the calculation of effective thermal resistance of the wall assembly, allowing builders to take advantage of the additional thermal resistance provided by the air cavity.
Continuity of insulation
The National Plumbing Code and related provincial-territorial regulations require plumbing fixtures to be vented. Some of them are often installed on or close to an exterior wall. The minimum possible size for vent pipes is 1¼ in., which results in an outside diameter of 1⅝ in. With 5½ in. wall framing, this leaves a maximum 3⅞ in. for insulation. For various reasons, 1½ in. vent pipe, with an outside diameter of 2⅛ in. is often used, leaving a maximum 3⅜ in. for insulation, which may not meet the minimum required insulation thickness set in the Code.
Exceptions are added to allow the trade-off path to be used in areas of the wall where there are other components such as pipes, ducts and electrical components to permit a relaxation of the effective RSI values.
The proposed reduction in insulation at plumbing (vent/drain/waste) pipes, conduits, electrical outlets and switch boxes is very small relative to the overall energy use of the building.
The relaxations are based on the assumption that the other Code requirements (such as condensation control and risk of freezing) are met.
Equipment performance requirements
Requirements and standards in Section 9.36. for HVAC and service water heating equipment did not align with the current minimum Canadian standards for manufacture, making it difficult for Code users to demonstrate compliance.
Therefore, the requirements for the performance of HVAC and service water heating equipment are updated to align with the federal energy efficiency regulations.
As many of the available products in the Canadian marketplace already meet these higher requirements, this update synchronizes Code requirements with the development of the industry, making it easier for readily available products to demonstrate compliance with the Code.
EnerGuide Rating System (ERS)
Some of the assumptions used in the NBC 2015 did not reflect the latest research in housing and were not aligned with those used in Natural Resources Canada (NRCan)’s EnerGuide Rating System (ERS). The absence of such alignment resulted in loss of benefits from access to available tools, network of energy advisors and opportunities for simplifying the use of performance modeling.
The NBC establishes ERS as an acceptable compliance path. This will reduce burden for builders by ensuring those who voluntarily use ERS for labeling will not be required to complete duplicate energy modeling to demonstrate compliance with the Code, and enabling energy modelers to use the automatically generated reference building that is part of ERS procedures, rather than manually modeling a reference and proposed building.
In addition, aligning Code with the ERS procedures for new buildings will streamline Code compliance for builders who voluntarily use the ERS. It is worth noting here that energy modeling software other than those referenced in ERS could also be used to demonstrate compliance with the Code.
Overall, these changes will reduce confusion in the industry, avoid possible barriers and facilitate energy-efficient construction.
Tiered energy performance compliance
The 2020 edition of the NBC introduces tiered energy performance compliance. This is a departure from the traditional approach of the National Model Codes establishing the minimum acceptable requirements.
Tiered energy performance compliance responds to the market needs to provide a voluntary pathway for regulators who want to go above and beyond the minimum Code requirements.
This will
- help to progressively increase overall energy efficiency of houses and buildings,
- guide proactively industry to respond to future market demands for high-efficiency solutions,
- provide a nationally harmonized metric for measuring energy performance improvement.
Tiered energy performance compliance is comprised of minimum base Code requirements and pre-determined performance levels or tiers.
Tiers are defined in terms of the percent improvement as well as energy consumption of the building. However, for simplicity, we will refer only to energy consumption of the building in this presentation.
The first tier is the same as the minimum base Code, representing the 2020 edition of the National Building Code of Canada (NBC).
The energy consumption is then reduced by a percentage in successive tiers as shown on the slide. These percentages were selected to approximate the energy-saving targets of market programs.
Tiered energy performance compliance provides predictable future energy performance requirements which are to remain fixed in time.
Different performance tiers allow builders and regulators to choose the performance level that best suits their needs.
It is recognized that some home builders might not have access to tools and expertise to conduct energy modeling and simulations. To overcome this barrier, the 2020 edition of the NBC provides a separate prescriptive path, to complement tiered energy performance compliance.
This new path is based on energy conservation measures and points. It lists a number of energy conservation measures that have energy conservation points associated with them. It allows Code users to select measures that enable them to accumulate sufficient points to achieve a desired level of tiered energy performance compliance.
Currently, this path is available for Tier 2 only and will be extended to other tiers in the 2020–2025 code cycle.
Conclusion
This concludes the presentation about important changes to energy efficiency in Section 9.36. of Division B of the National Building Code of Canada 2020.
How to get involved
To participate in the code development process, visit the CBHCC’s website to find information about upcoming events and meetings, to submit a code change request, to comment on proposed changes during an open public review, or to volunteer to participate on a code development committee.
How to access the codes
The National Model Codes are published by the National Research Council of Canada.
Visit Codes Canada’s publications web page on the NRC’s website to purchase a paper copy of the Codes or to access them in free electronic format.
Thank you.