Important Changes to Parts 5 and 6 of the NBC 2020

(Kevin) Hsiao-Feng Wu, Technical Advisor, Codes Canada

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Video transcript

Introduction

Hi, my name is (Kevin) Hsiao-Feng Wu 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 am 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 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.

This presentation will focus on important changes to Parts 5 and 6 of the National Building Code of Canada 2020.

NBC 2020, Part 5: Outline

Here is an outline of the significant changes introduced in Part 5 of the National Building Code of Canada (NBC) 2020.

NBC 2020, Part 5: Air leakage

The Section on air leakage was totally revamped to:

  • shift the current focus on the performance of air barrier materials to the performance of air barrier assemblies;
  • describe the expected performance of all air barriers;
  • provide a method for standardized testing of both proprietary and generic assemblies; and
  • provide guidance on air barrier systems.

The total overhaul of the Section on air leakage offers—for the first time—codification and clarification of known approaches and better reflects the current practice.

NBC 2020, Part 5: New material standards

A number of new material standards were added.

They cover:

  • spandrel glass;
  • insulated concrete forms;
  • exterior gypsum panel products for use as sheathing; and
  • asphalt-coated glass-based sheets for roofing.

These materials have been used in practice where there was no clear means of compliance in the past. Adding these references in the NBC 2020 eliminates the inconsistency in applications and reduces the workload for professionals in determining Code compliance.

NBC 2020, Part 5: Outdated and withdrawn standards

Outdated and withdrawn standards were dealt with in two different ways.

The first way is replacement with more up-to-date and relevant standards.

This was done for:

  • hardboard siding;
  • asphalt shingles; and
  • hardboard cladding.

The second way is deletion without replacement as no replacement or no adequate replacement is available or the material is covered by another standard.

This was done for:

  • light and heat-reflecting glass and wired safety glass;
  • steel sheet siding; and
  • selection of liquid-applied sealants.

NBC 2020, Part 5: explanatory Notes

The last set of changes included in Part 5 of the NBC 2020 updates explanatory Notes on:

  • resistance to deterioration to add a new guideline;
  • installation and field testing of windows, doors and skylights to harmonize with relevant standards referenced in the Code; and
  • sealing and drainage to remove ambiguous terms and provide more current information and guidance.

NBC 2020, Part 6: Outline

There are two important changes in Part 6 of the NBC 2020:

  • Ventilation requirements have been revised and clarified, and new requirements for exhaust ventilation have been added.
  • New requirements have been introduced to address the growth and transmission of Legionella bacteria in buildings.

NBC 2020, Part 6 (HVAC): Ventilation

References to ANSI/ASHRAE 62, “Ventilation for Acceptable Indoor Air Quality,” were introduced in Part 6 of Division B of the NBC 1995. The edition year of the standard was last updated in the NBC 2005 when the 2001 edition of the standard was current.

The standard’s edition year has not been updated in the NBC since then, as a comprehensive technical review of subsequent published editions in 2004 and 2007 were found to be problematic. However, the minimum ventilation rates in ANSI/ASHRAE 62-2001 are no longer applicable. In addition, the 2001 edition of the standard does not address the building’s contribution to indoor air quality.

ANSI/ASHRAE 62.1-2016 was reviewed and found to be acceptable for referencing in Part 6. This updated standard is based on current assumptions, recent technologies and current industry practice.

ANSI/ASHRAE 62.1:

  • acceptably addresses the issues previously deemed problematic in Addendum N of ANSI/ASHRAE 62;
  • addresses both primary indoor sources of contaminants;
  • deals with impact on occupant health;
  • considers outdoor air quality used for ventilation purposes (as the NBC does); and
  • introduces different methods of determining ventilation.

Thus, the 2016 edition of ANSI/ASHRAE 62.1 is now referenced in the NBC.

NBC 2020, Part 6 (HVAC): Natural ventilation

The requirements for natural ventilation were deemed to be vague and unenforceable, as well as overly and unreasonably restrictive. A review of the existing requirements for natural ventilation and those related to natural ventilation in section 6.4 of ANSI/ASHRAE 62.1-2016 led to the conclusion that referring to ANSI/ASHRAE 62.1 was more appropriate, consistent and easier to enforce. However, as in the original requirement, residential occupancies are excluded.

NBC 2020, Part 6 (HVAC): Exhaust ventilation

In addition to clarifying the requirements for natural ventilation, the updates to ANSI/ASHRAE 62.1 introduce requirements for exhaust ventilation, on which the NBC was silent.

The requirements allow for adequate ventilation of the indoor environment (that is, supply of outdoor air, amount of indoor air exhaust), which includes adequate control of humidity and/or contaminants of concern.

Consequently, the standard limits the negative effects on the air quality of indoor environments as well as adverse health effects to the occupants.

These changes to the ventilation requirements provide more efficient good engineering practice that reduces the need for outdoor air, which in turn reduces the energy consumption needed to condition the air, in turn resulting in lower operating costs.

NBC 2020, Part 6: Legionella

A number of changes address the growth and transmission of Legionella bacteria in buildings. Legionnaires’ disease is a potentially fatal respiratory illness that is caused by exposure to Legionella bacteria.

These changes are intended to minimize adverse health effects caused by Legionella and other bacteria. They represent a massive effort and partnership with Health Canada and Public Services and Procurement Canada to come up with a solution that suits everyone.

The changes:

  • clarify design requirements for evaporative equipment in different applications to address health risks—such as those associated with Legionella;
  • specify that cooling tower blowdown products must be located not less than a specific minimum distance from outdoor air intakes and be connected to the building’s drainage system;
  • include requirements that help prevent the introduction of warm discharge air and associated drifts that may contain biological contaminants to indoor environments via outdoor air intakes;
  • contain requirements that mitigate the growth and dispersion of Legionella and protect potable water sources;
  • require that evaporative equipment be provided with service platforms, access ports, fixed ladders, and restraint connections so that visual inspections, maintenance and water testing may be carried out on this equipment.

These changes involve additional costs for the manufacturer in the design of evaporative air coolers, misters, atomizers, air washers and humidifiers, representing 3% to 5% of the full system cost. These additional costs are mainly related to designs that avoid water stagnation to reduce or limit the potential for Legionella growth.

Conclusion

This concludes the presentation about important changes to Parts 5 and 6 of the 2020 edition of the National Building Code.

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 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.

Date modified: 2025-02-22