CSA S500:21 Thermosyphon Foundations for Buildings in Permafrost Regions

In 2014, the Standards Council of Canada’s Northern Infrastructure Standardization Initiative (NISI) funded the Canadian Standards Association (CSA Group) to develop a standard for the design and implementation of thermosyphon foundations to support buildings facing changing and unstable permafrost conditions as a result of climate change. The Canadian north is experiencing several building engineering problems which need to be addressed now to avoid worsening problems in the future. Infrastructure is being affected by climate change impacts like permafrost thaw, coastal erosion, and changing temperatures and precipitation patterns. With growing concern of climate change and the warming of the planet, thermosyphons are one way to ensure the ground under buildings remains stable and safe. Originating in Alaska in the 1960`s, and coming to Canada in the 1970`s, the opportunity to apply this technology is well-suited to respond to and counter the concerns of degrading permafrost damaging building foundations. Previous to this standard, entitled CSA 500 Thermosyphon foundations for buildings in permafrost regions, there were no national standards for the design, construction, and maintenance for thermosyphon supported foundations. The standard is supported by another northern-specific guide – CSA Plus 4011 Technical Guide – Infrastructure in permafrost: A guideline for climate change adaptation – that was developed with funding from NISI to provide northern designers with an understanding of how to adapt infrastructure to a changing climate.

Identifying Actions

The clear need for thermosyphon foundation guidelines led to the Standards Council of Canada’s NISI to work with its Northern stakeholders to outline a set of needs for a new thermosyphon standard. They then funded CSA Group to develop a new standard, with the help of northern building experts, on the topic. Established in 2011, NISI is an initiative that works with communities, standards development organizations, and experts primarily from across northern Canada to support the development of standards that are effective in addressing climate change impacts to northern infrastructure design, planning and management. Each standard helps building owners and operators, as well as those responsible for public and community infrastructure, build and maintain infrastructure in a changing climate. NISI is guided by a Northern Advisory Committee (NAC) that is composed of representatives from each of the territories that have a role in community and public infrastructure. This standard was developed by the CSA Group-run Subcommittee on Thermosyphon Foundations for Buildings in Permafrost Regions under the jurisdiction of the Technical Committee on Northern Built Infrastructure. The Subcommittee and Technical committees are composed of government, academia, engineers, and consultants. The NAC outlined the need for this standard, and SCC worked with the NAC as well as other stakeholders to develop a “wish list” for a new standard. The development of National Standards of Canada (NSCs) makes use of international standard development best practices and safeguards the interests of Canadians. Steps in the NSC development process include:
  • identifying the need for the standard
  • reviewing the existing standards landscape
  • engaging affected stakeholders
  • notifying the public at the project start
  • developing the standard (by technical experts)
  • publicly consulting on the proposed standard
  • disposition of comments and revision as applicable by the technical committee
  • vote and approval by the Technical Committee of the NSC
  • prompt publication
  • maintenance of the NSC
The maintenance cycle of NSCs means that every five years, the standard must either be updated, confirmed as is, or withdrawn. As a result, the standards are continuously reviewed to include the latest knowledge and technology, making them a strong tool for northern communities.


The CSA S500:14 Thermosyphon foundations for buildings in permafrost regions standard was developed in compliance with Standards Council of Canada requirements for National Standards of Canada and was published as a National Standard of Canada by CSA Group in 2014 and updated with a new edition published in 2021. This Standard provides requirements for all life-cycle phases of thermosyphon foundations for new buildings on permafrost, including site characterization, design, installation, and commissioning phases as well as for monitoring and maintenance phases. It is meant to ensure the long-term performance of thermosyphon-supported foundation systems under changing environmental conditions due to climate change. The objectives of this Standard are to:
  1. specify performance expectations for thermosyphon foundations together with monitoring requirements necessary to support an appropriate maintenance program;
  2. specify the materials to be used in thermosyphon foundations;
  3. foster an awareness and understanding of application technology, with a focus on factors that could compromise the functionality of foundation systems reliant on thermosyphons;
  4. describe the typical phases of the life cycle of thermosyphon foundations for buildings on permafrost, including design, installation, commissioning, monitoring, and maintenance;
  5. provide guidance to maximize the long-term viability of thermosyphon-supported foundation systems under changing environmental conditions
This standard is applicable to new buildings on permafrost sites. It is not intended to provide guidance for initial selection of the most appropriate foundation type for any particular structure on a permafrost site. It is assumed that a thorough review of alternative foundation systems has been undertaken and that that the site has been categorized as potentially thaw-unstable.
Exclusions: This Standard does not cover
  • abandonment/demolition of buildings with thermosyphon foundations;
  • thermosyphons in areas of non-permafrost or retrofitting thermosyphons to existing buildings; and
  • thermosyphons used for infrastructure other than buildings.
However, aspects of the Standard could be useful in these applications.

Outcomes and Monitoring Progress

The first edition of CSA S500 may be referenced in the 2020 edition of the National Building Code of Canada (to be confirmed following publication later this year). It was also referenced in the Société d’Habitation du Quebec’s Housing Construction in Nunavik – Guide to Good Practices, as well as in the Northwest Territories Good Building Practice for Northern Facilities requirements.
Arctic Foundations of Canada Inc., the manufacturer of thermosyphons in Canada, ensures that CSA S500:14 (the first edition) is followed on every building related installation they have performed since 2014 (adherence is specific to their portion of the work i.e. final review, modelling, design, manufacturing, and installation).
Further, the first edition of this standard is referenced in CSA S6:19 Canadian Highway Bridge Design Code, CSA S6:19 Commentary to the Canadian Highway Bridge Design Code, and in the new Yukon Government Design Standards Manual. The standard was used in the following projects:
  • Qikiqtani Correctional Healing Centre Expansion – Iqaluit, NU
  • Arctic Bay Fire Hall – Arctic Bay, NU
  • Kugaaruk Fire Hall – Kugaaruk, NU
  • Rankin Inlet Airport Maintenance Garage – Rankin Inlet, NU
  • Igloolik High School – Igloolik, NU
  • Tununuk Apartments (Thermopiles) – Inuvik, NT

Next Steps

CSA 500:21 Thermosyphon foundations for buildings in permafrost regions was updated in 2021 to include new information on climate change, clarify the thermal analysis discussion, and clarify the distinctions and engineering considerations between various types of thermosyphons. The standard can be downloaded at no charge here.

Climate change is continuing to impact northern communities, and communities need tools to adapt. To date, thirteen standards and technical guides have been funded under NISI to support building in permafrost, dealing with extreme weather (like high winds), design with climate change and risk in mind, and to support the design of community systems like solid waste sites and drainage systems.

NISI provides practical, on-the-ground solutions that are written by experts in the field and specifically geared for the north. The standards have been written to recognize the geographic isolation, climatically hash nature of the region, and the need for efficiency and resiliency.

Once new standards are published, SCC works with its project partners to provide in-class training, free of charge, easy-to-understand guides, and online training modules such as webinars to introduce northerners to the standards.