A building’s thermal performance requirements are determined by the climate in which the building is situated. This climate can be described by Climate Zones. The projected shifts in Building Climate Zones due to climate change provide a high-level understanding of changing energy consumption patterns in buildings, highlighting that reliance on historical climate data alone for design is no longer sufficient.
Climate zones refer to a spatial or regional classification system based on certain climate characteristics. Building professionals use climate zones to specify the thermal performance requirements for their design based on the amount of heating, or sometimes cooling, required. This approach enables the development of buildings that are suited to perform adequately given the thermal environmental loads of the region while complying with the energy efficiency requirements of the Building Code.
Building codes require compliance to energy codes and standards, such as the National Energy Code of Canada for Buildings (NECB), to provide minimum energy performance requirements. These performance requirements are keyed to Building Climate Zones. The NECB’s Building Climate Zones are determined using six Heating Degree-Day (HDD) categories, shown in Table 1.
The HDD is the cumulative number of degrees Celsius that a day’s average temperature is below 18°C during an entire year. For example, if the daily average temperature is -10°C, the heating degree-days for that day is equal to 28. However, if the daily average temperature is above 18°C, the HDD value for that day is zero. HDDs are then added for every day of the entire year and averaged over a multi-year period.
The HDD metric describes the average annual heating demand for a building in a specific location. Higher HDD, or a higher Climate Zone number, corresponds to a greater heating energy requirement, which means that a higher level of enclosure thermal performance is required. For example, Climate Zone 8 is the coldest zone, so Zone 8 buildings typically require more insulation compared to buildings in Zone 4, the warmest zone.
| Zone | Heating Degree-Days of Building Location, Celsius Degree-Days |
| 4 | < 3000 |
| 5 | 3000 to 3999 |
| 6 | 4000 to 4999 |
| 7A | 5000 to 5999 |
| 7B | 6000 to 6999 |
| 8 | ≥ 7000 |
The NECB’s thermal criteria and Climate Zones are based on ANSI/ASHRAE/IES 90.1, ‘Energy Standard for Buildings Except Low-Rise Residential Buildings’. ASHRAE Climate Zones are familiar to architects, builders, and engineers. ASHRAE uses Heating Degree Days (HDDs) as well as Cooling Degree-Days (CDDs), Monthly Mean Temperature, and Monthly Precipitation to assign its zones. This means that ASHRAE Climate Zones are slightly different from NECB zones, and the classification also includes moisture definitions (moist ‘A’, dry ‘B’, and marine ‘C’). Several provinces like Ontario and British Columbia provide pathways for achieving energy efficiency compliance that can be pursued through either the National Energy Code of Canada for Buildings (NECB) or the ASHRAE 90.1 standard.
Climate Zones are used to help ensure that buildings are energy efficient. However, with global warming that has already occurred and will continue in future, Building Climate Zones based on historical climate data alone do not represent the climatic reality that buildings will experience throughout their life cycle. Reduced Heating Degree Days mean that buildings require less heating now, and in the future, than they did in the past. Many locations in Canada could shift to <3000 HDD or even <2000 HDD levels. For this reason, building designers need to consider if more cooling may be required. It is important to keep in mind that even if your location stays within the same climate zone over time, Heating Degree Days may still be changing, as Building Climate Zones are broad categories.
Without considering future climate data, overheating may be hazardous if cooling systems are absent or undersized. Even high-performance buildings will fail to perform optimally and face future climate impacts if they are designed based on historical climate data only. The transition towards using future climate data, future weather files, and climatic design values can help ensure that the sizing of mechanical cooling systems and enclosure performance requirements are optimal.
The Building Climate Zones on ClimateData.ca provide a high-level view of how some energy demands are projected to change in the future, supporting proactive steps to consider and use future climate data when designing buildings in Canada.
In Canada, the responsibility for regulating building design and construction lies with the provinces and territories within their respective jurisdictions. They have the authority to adopt and enforce the National Model Codes, such as the National Energy Code for Buildings (NECB) or develop their own codes that may have different requirements from the National Model Codes. Building designers must always consult the local jurisdiction to determine what codes and standards must be met.
If you are interested in determining and visualizing future climate zones for a specified location, the Building Climate Zones variable on ClimateData.ca can provide high-level guidance, based on statistically downscaled Heating Degree Day data. Following best practice when using future climate data, make sure to consider a range of scenarios and percentiles from the multi-model ensemble.
Additional, detailed future climate data can also support pro-active resilient building design, including:
Future Weather Files: If you are interested in using performance-based metrics for code compliance, future weather files for building performance simulations are now available through the Pacific Climate Impacts Consortium (PCIC) and the National Research Council of Canada (NRC). For guidance on which dataset to use, see “Guidance on Using Future Climate Data for Building Performance Simulation”.
Future Design Values: To meet standards of care around designing for a changing climate, future climatic design data are also available. The Design Value Explorer (DVE) tool provides future HDD and other technical projections for Table C-2 in the National Building Code of Canada (NBCC). The future DVE values were developed through a National Research Council Canada (NRC) collaboration with Environment and Climate Change Canada (ECCC).
Still have questions about which future climate data to use in building design? Contact the CCCS Support Desk.