Canada's National Building Code & Climate Change: Safer Design
Climate change is bringing about shifts not only to global temperatures, but also in weather patterns, including winds, snowfall, heavy rainfall, wildfires, among others.
These changes pose an emerging risk for the structural integrity of buildings and the way engineers design and build structures in our cities – especially when the climate changes occur faster than updates to building codes and regulations.
Traditionally, structural engineers relied on national building codes to ensure safe building design. In Canada, the National Building Code (NBC) contains the rules and regulations that apply to the design and construction of all real estate projects and buildings. It is important in ensuring the safety, health, accessibility and the environment of buildings and occupants.
The challenge is that there is currently no guidance given in the building code on climate change. While that is expected to change in the future, all provisions in the code are based on the current state of weather and climate in Canada. However, without considerations of future climate patterns, including changes to extreme weather, the codes should be viewed as the bare minimum to creating resilient buildings. Resilient building design does not just mean “up to code” but it means that the structure can withstand extreme weather including from severe wind, heavy rainfall, and wildfires.
So how can you build resiliency into your building design?
Understanding the regionality of climate change and the impacts on building design
Certain weather patterns are more common in certain regions. In Canada, for instance, hurricanes impact the Atlantic provinces, while tornados primarily impact Southern Ontario and southern parts of the Prairie provinces (Alberta, Saskatchewan, and Manitoba).
Not only will a designer need to consider the environment where the building will be built, but also the long-term weather impacts of the region and the type of extreme weather events that are likely to occur there. Meteorological and historical data would be important to have here, but so too would projections of the likelihood of future such events.
The current building code provisions are based on the assumption of a stationary climate. In a changing climate it also becomes necessary to define the period of time over which the climatic variables will be evaluated. For example, should snowfall patterns and the associated impact on snow loads be evaluated for 20 years? Is 30 years better? 50? While snow loads are typically based on a 50-year return period, there are no formal requirements currently for the assessment of the base climate variables.
So how do you ensure that a building design accounts for changes to wind speed and snowfall over time when often the very nature of climate change is that it is unpredictable? A major factor is modeling climate change scenarios and what that would do to wind speeds and snowfall amount. Let’s break it down further by the type of weather event:
How can I design buildings that are resilient to wind loads?
Wind load refers to the load that is placed on the exterior of a structure by wind.
The way the National Building Code in Canada currently treats wind loads is as basic wind speed – a certain probability of wind – but this assumes no change to climate. Beyond regular wind speed loads, there is also a need to consider extreme wind events, specifically hurricanes and tornadoes.
When it comes to wind loads, it is critical to separate basic wind speed from wind events. Separating the mechanisms that create wind (i.e. thunderstorms), from both regular wind and extreme wind events (hurricanes, typhoons, tornados) is crucial as climate change will affect each of these differently. Most building codes - including Canada’s NBC - currently treat all of these the same.
Partnering with an expert in wind engineering to conduct a wind tunnel test early in the design stage is one of the best ways to reduce environmental risk, while also saving you time and money during the project.
Careful attention to the effects of wind, snow, ventilation, vibration and related microclimate environmental issues on buildings and structures are crucial. But most importantly, it can ensure a resilient design that will withstand even extreme changes to climate.
How will snowfall & snow load impact building design?
Anyone who has had to shovel after a heavy snowfall understands that any extreme changes in snowfall trends are going to impact building design.
When discussing how snow interacts with a structure, we need to consider two key terms: snowfall and snow load. Snowfall refers to a single snow event, such as a snowstorm, while snow load refers to the accumulation of snow over a period of time and the resulting downward force from the weight of snow and ice on a building's roof. Many regions prone to high snowfalls are seeing less snow loads as a result of climate change – but also more frequent and heavier snow events. With climate change, storms are getting more frequent as a warming planet means more precipitation. We are also seeing larger snowfall events in unexpected regions in the southern U.S.
Not only is there a trend toward more frequent snowfalls, there is also an emerging pattern of more melting in between snow events. This could have a significant impact on how buildings are designed as drifting snow around the building, the kind that can accumulate on rooftops, changes with temperature fluctuations. If snow goes through a thaw cycle, and then freezes, it won’t drift. In addition, melting and freezing cycles cause ice to form on top of buildings, which can fall and pose a great safety hazard to building occupants and pedestrians.
Local building codes and standards give guidance for snow loads. However, these codes are based on historical observations of snow on the ground surface and existing roofs. A building with a more intricate or larger shape or with improved thermal performance requires new interpretations. In addition, codes can’t directly address the complex, combined effects of wind and other climate factors.
A snow loading analysis can help quantify wind, climate, and thermodynamic factors to address the effects of accumulated snow on a building design. Getting the loading right at the design stage can save a lot of money in structural materials. More importantly, it ensures the structure is safe. It is important that the analysis takes into account the specifics of the local climate, surroundings, building shape and construction. This approach provides design snow loads that are “better than code.”
How can you ensure resiliency in your building design?
As the conversation around climate change and the impact on the built environment continues, designers are seeking guidance from climate engineering specialists to understand how best to design for a future state, one that takes the evolving climate – particularly related to wind and snow - into consideration.
Progressive designers and engineers understand that localized data is invaluable in the early stage of the design process. Studies that are not only site specific but also apply climate factors and changes will prove to save cost and ensure resilient and safe buildings in the long run.
Ultimately, a forward-looking approach to building design is crucial to creating resilient structures and cities in the ever-changing reality of climate change.
RWDI is proud to be working with governments at the national and municipal levels, including Canada's National Building Code, to update codes and guidelines to reflect the evolving changes to climate.
Want more information on how we can help you design for the future? Explore one of our climate services below to get started:
- Snow loading
- Falling ice and snow
- Wind tunnel testing
- Wind load effects on structures
- Wind load effects on façade systems
This post is part of our ongoing climate changed blog series. We encourage you to follow RWDI on Linkedin to stay informed of future posts and to reach out if you have a challenge you would like to discuss.