By: Shandler Kohlman
As our global community becomes more aware of the pressing need to reduce energy consumption, the requirement for optimized buildings continues to grow and is playing a significant role in the development of building codes in Canada. It can be difficult for owners to keep up with changes and for many to understand how to meet shifting requirements.
The 2011 National Energy Code for Buildings (NECB) was passed on November 1st, 2015. The 2011 NECB was the first energy code in Canada, providing requirements for the design and construction of energy-efficient buildings. An example of changing requirements is illustrated in the most recent version of the energy code, 2017 National Energy Code for Buildings, which was passed on January 1st, 2020. The latest release of the NECB has placed more importance on thermal bridging and how it interacts with buildings and their energy performance, as illustrated through energy modelling.
In the previous energy code, only thermal bridges that were greater than 2% of the building envelope area were accounted for; however, the new energy code now includes, for the most part, all thermal bridges. The new requirements in the 2017 NECB are an example of the growing demand and need to optimize buildings that impact the cities and communities in which they’re situated.
What is Thermal Bridging?
Thermal bridging occurs when heat escapes at a higher rate due to a break in a building envelope’s thermal barrier. Architectural design intent, structural requirements, as well as constructability challenges and resource availability, can all cause thermal bridges. Typically, thermal bridges are found at protruding balconies, at floor transitions, around fenestrations (windows/doors), through structural components, corner framing assemblies, canopies, and changes in wall assemblies or within cladding systems. Thermal bridging can lead to increased energy demands to condition a building, result in cold areas within a building, and potentially increase the risk of condensation and frost forming inside a building.
Materials and Assembly Selection
Given the changes in the latest version of NECB, and the desire to reduce the energy required to condition our buildings, thermal bridges should be avoided whenever possible. Where possible, the structural components should remain on the warm side of the building. Using continuous insulation on the exterior of the building helps to achieve this. Select materials that include higher resistance to heat flow, or a higher R-value. Where a thermal bridge is anticipated, consider installing a thermal break to limit the heat transfer through the building envelope. An example of this is using a fibreglass clip system to connect metal cladding to your walls instead of a steel Z-girt. Fibreglass resists heat flow at a much higher rate compared to steel.
Design
Identifying and understanding the impact of thermal bridging on the overall performance of a building in the early design stage also helps make educated decisions on a building’s design. In addition, engaging with essential consultants such as building envelope and energy modelling experts early in the conceptual and design stage of a construction project is vital. By including subject matter experts early on in the design process, strategies can be developed to limit thermal bridging while keeping the long-term building envelope performance in mind. By working together, both building envelope and energy modelling experts not only help reduce construction costs by accurately identifying and modelling specific thermal bridges on a building to meet code requirements, but they also find efficiencies in the construction assemblies and details used.
The new requirements laid out in NECB 2017 supports Canada’s energy efficiency goals and objectives for new and existing buildings. As our global society desires a more energy-efficient built environment, building owners need to be vigilant in their efforts to meet government codes and standards while ensuring that communities remain resilient and that their future is sustainable. Our extensive experience in designing energy-efficient buildings provides us with a unique perspective that enables our team to provide customers with cost-effective strategies, solutions for meeting codes and standards and designs that consider long-term durability and sustainability. Specifically, with the more considerable demands placed on the building envelope under NECB 2017, our team of energy modellers and building envelope specialists is well suited to take on this challenge.
Keeping ourselves and our customers informed of the latest developments and regulations, in addition to understanding the growing and diverse demands of various stakeholders, remains crucial to our team’s ability to deliver quality solutions that facilitate the success of our customers and their respective communities while we continue to engineer sustainable cities that are safe, inclusive and resilient.
