* This rationale was developed and provided by the Joint Task Group – Harmonized Variations for Mass Timber. Any question pertaining to the public comment period, the proposed changes and the related rationale should be sent by email to the Joint Task Group.

Advancing EMTC provisions

Problem

The 2020 National Building Code of Canada (NBC) has adopted Encapsulated Mass Timber Construction (EMTC) as a construction type distinct from combustible or noncombustible construction, and provisions for its use have been outlined.

With the supporting research and real-world application of this construction type rapidly expanding, the 2020 NBC provisions could already be considered unduly restrictive at the time of publication. Many EMTC buildings, both in Canada and around the world, have already been constructed which exist outside the acceptable solutions of the 2020 NBC with respect to area, height, occupancy and so forth. These buildings have demonstrated compliance with the underlying objectives of the Code.

Both the 2021 and upcoming 2024 editions of the International Building Code (IBC), have significantly expanded provisions for the use of EMTC in comparison to the 2020 NBC. The following suite of proposed code changes intends to roughly mirror the provisions contained in the 2021 and 2024 IBC editions and represents the next logical and safe expansion of existing EMTC articles in Canada.

Justification – Explanation

The attached Transferability Report contains extensive discussion on the rationale of the transferability of the IBC Type IV-A, IV-B, and IV-C provisions to the NBC. The Transferability Report, substantiated by a study on the comparative differences of the IBC and the NBC in the Fire and Structural perspectives, concluded that the NBCC can adopt the IBC Type IV-A, IV-B, and IV-C provisions with careful, and in most cases, more conservative modifications. Furthermore, research performed since the original adoption of EMTC [1][2][3][4] and a new material standard for CLT [5] supports its increased safe application.

Adoption and Uniformity

This proposed code content will act as a test case to demonstrate agile and responsive code advancement aligned with PT priorities under the new Construction Codes Reconciliation Agreement (CCRA). The code content will be offered to Provinces and Territories (PT) for early adoption, with the assumption that similar content will be incorporated into the national model codes in full during the next cycle.

Impact Analysis

EMTC buildings continue to achieve the same performance level regarding safety, health, accessibility, fire and structural protection, and environment objectives as other types of buildings addressed in the NBC 2020.

The benefits of increasing permissions for EMTC are numerous. Many of them echo those presented in the original package of code changes introducing EMTC to the NBC.

Environmentally, EMTC has demonstrated a marked decrease in its carbon impact in comparison with traditional construction materials and methods. Recent studies [6] show a 25% reduction in global warming potential in comparison with concrete buildings. Wood is a renewable resource that naturally sequesters carbon. Increased use of wood and prefabricated components in construction have therefore become key tools in combatting climate change and complying with ever more stringent requirements for energy efficiency and reduced carbon use.

Wood is also a natural insulator and has better thermal performance than masonry or concrete. Thermal bridging is greatly reduced in wood structures.

Prefabrication offers further benefits on its own: Reduced construction timeframes minimize both the cost of construction and its impact on the surrounding community; The amount of construction waste is also dramatically reduced. The reduced construction timeframes associated with prefabrication have the potential to address housing affordability.

Research into the concept of biophilia has revealed benefits to health, well-being and even productivity that comes from the proximity to natural materials attained through exposing wood in EMTC buildings. [7]

Allowing for taller buildings in the same footprint is more cost-effective and allowing for a greater range of occupancy types expands EMTC as a competitive option.

Adding enhanced prescriptive options for EMTC reduces the need for multiple alternative solutions, which are already regularly being provided by consultants.

Specifically, this proposal stands to increase the number of EMTC buildings being built and multiply the above benefits.

As this proposal only includes enabling provisions that are optional for code users, impacts are deemed to be minimal.

Even a hundredfold increase in the amount of mass timber buildings being constructed in Canada would not cause a notable disruption to the industries of more traditional construction materials or their economic viability, especially as these materials continue to be employed at least partially in EMTC projects.

Costs

This code content is enabling and does not impose mandatory requirements or new restrictions. Therefore, it doesn’t impose new costs. However, adoption of these provisions is anticipated to reduce costs and make EMTC more appealing as a construction type.

Enforcement Implications

As the proposed changes represent an extension of already existing guidelines, no unusual enforcement implications are anticipated.

Who is Affected?

Anyone concerned with the design and construction of EMTC buildings, namely architects, engineers, building owners and regulators. Further, as a renewable resource with a markedly lower carbon footprint when compared to traditional construction materials and methods for higher/taller buildings, the promotion of EMTC stands to benefit all, including the public. Public engagement process to be held and a “What We Heard” report completed in fall 2023.

Attached Supporting Material

See attached “Transferability of 2021 International Building Code” Report by GHL Consultants and Fast + Epp Structural Engineers (“Transferability Report”).
See attached “Technical Peer Review of Transferability Report” (Technical Peer Review) by Senez Consulting.

References

[1] Large-scale fire tests of a mass timber building structure for MTDFTP (2023) Su, Joseph; Gibbs, Eric; Weinfurter, Mark; Lafrance, Pier-Simon; Gratton, Karl; Frade, Andrew; Leroux, Patrice

[2] RISE Fire Research: Fire Safe Implementation of Visible Mass Timber in Tall Buildings – Compartment Fire Testing (2021) Daniel Brandon, Johan Sjöström, Alastair Temple, Emil Hallberg and Fredrik Kahl

[3] Structure Fires in British Columbia: Exploring Variations in Outcomes as a Function of Building Height and Life Safety Systems (2019) Garis, Len; Clare, Joe; Biantoro, Chris, Centre for Public Safety and Criminal Justice Research

[4] Fire Severity Outcome Comparison of Apartment Buildings Constructed from Combustible and Non-combustible Materials (2022) Zheng, Alex; Garis, Len; Pike, Ian, Centre for Public Safety and Criminal Justice Research

[5] ANSI/APA (2019) PRG 320-2019. Standard for Performance-Rated Cross-Laminated Timber, American National Standards Institute, APA – The Engineered Wood Association, Tacoma, WA

[6] Journal article: Lessons Learned from the Life Cycle Assessment and Life Cycle Costing of mass timber at UBC (2018) Teshnizia et al.

[7] The nature of wood, an exploration of the science of biophilic responses to wood (2022) William D. Browning, Catherine O. Ryan & Claire DeMarco, Terrapin Bright Green TM.

Links to the proposed EMTC changes: