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Guidance on Using Future Climate Data for Building Performance Simulation

Many designers rely on the output of building performance simulations to inform design decisions. These simulations use climatic data contained in weather files, which are normally based on historical climate from observations. To be future-ready, simulations using only historical climate data are no longer adequate and designers will need to also use future weather files. Learn about the two types of future weather datasets and their design applications for Canada.

Module

Designing Future-Ready Buildings

Format

Article

Time to completion

10 minutes

Key Messages

Using historical weather files may yield inaccurate results related to energy needs and occupant comfort. Simulations using historical files will generally underestimate cooling load, overestimate heating load, and inaccurately predict occupant comfort under future climate conditions.
To achieve climate resiliency, it is recommended to use both historical and future weather files in building simulation and design, as this enables buildings and their systems to withstand current climate conditions while also considering future vulnerabilities.
Two types of ‘future weather files’ are now available through the Pacific Climate Impacts Consortium (PCIC) and the National Research Council of Canada (NRC).
Choosing the appropriate future weather file dataset depends on the specific use: for example, future weather files should be selected based on the variable(s) that is important to users in their building energy simulation and design.

Why do we need to design for the future climate?

The shifting climate in Canada has the potential to transform weather patterns and temperature regimes in ways that could render buildings designed to the contemporary climate as inefficient, uncomfortable, or even unsafe. As Canada’s climate continues to change, buildings and their occupants face a host of challenges. These include considerable changes in energy needs for heating and cooling purposes. In addition, more frequent extreme daytime high temperatures due to climate change increase the risk of overheating in buildings during the summer months, particularly where cooling systems like air conditioning have not been required historically.

The building industry now faces an important challenge: to design buildings that are energy efficient and comfortable for all occupants in the current climate, yet are climate-resilient and continue to provide protection under future climatic conditions until the end of their design service lives.

Box 1.1 Overheating in British Columbia

Climate change impacts related to overheating have already been experienced directly through events such as the heat dome that occurred in British Columbia in 2021. The associated heat-related mortality was high with many buildings lacking cooling systems1. Climate-resilient buildings can help to mitigate negative climate change impacts on human health.

What are ‘Weather Files’?

A ‘weather file’ is used to describe the climatic conditions of a specific location and is critical input for building performance simulation. Commonly used weather files are based on a Typical Meteorological Year (TMY) method derived from historical climate observations. A TMY file represents a typical year of weather that is created by statistical selection and compilation of historical climate data from a multi-year period (typically spanning 15, 20 or 30 years). Refer to the next Learning Zone article for more information on TMY method.

While weather files have ‘weather’ in the name, actually, they are intended to capture long-term climate conditions. As many building simulations involve hourly calculations, the weather file consists of 8760 lines of data, one line for each hour in a non-leap year, for multiple variables. In Canada, historical weather files known as Canadian Weather Year for Energy Calculation (CWEC) – created using the TMY method – are the primary climate data used by building professionals in simulation and design. However, because these files are based on historical climate data, they are no longer sufficient to design future climate-ready buildings, and thus, there is a pressing need for building professionals to also use future weather files, which is becoming an increasingly expected standard of care.

BOX 1.2 Building performance simulation and the role of weather files

Building performance simulation, also known as building simulation, building energy modeling, building energy simulation, or building performance modeling, is an essential tool and required by many codes in designing buildings. Architects and engineers can analyze various building model designs on a computer under real-world conditions. To perform building simulation, two key inputs are required: a building model and a weather file. The weather file stores hourly information about building-relevant climate conditions, including dry bulb and dew point temperatures, relative humidity, air pressure, solar radiation, wind speed and direction, and cloud cover.

No matter how good your building model is, the use of a poorly representative weather file can give rise to unintended consequences. Inadequately designed buildings may have negative health impacts, increased energy consumption, and perhaps increased wear and tear on Heating, Ventilation, Air Conditioning (HVAC) systems.

Figure 1 shows the energy simulation results for a medium office building, comparing energy loads under current and future climates. The results indicate that cooling demand is expected to increase, while heating demand is expected to decrease, in both Toronto and Victoria. Additional simulation has shown this to be the case for other cities in Canada as well. These findings demonstrate the importance of designing buildings for future climate.

Figure 1

Building energy simulation of a medium office building for the selected cities using historical CWEC2016 (1998 to 2014), and PCIC’s future 2080s (2070 to 2100) weather files.

By making use of future climate data, we can ensure that buildings are designed to be energy-efficient, comfortable, and safe to use in the face of changing climate conditions. This means taking into account the potential impacts of climate change on the building’s performance and occupants, as well as designing strategies to address these impacts.

What future weather files are available?

Future weather files for various locations across Canada are now available from:

These future weather files are specifically intended for use in building simulation, like the current CWEC historical files.

What is the difference between the two future weather file datasets?

PCIC and NRC’s future weather files differ in terms of technical approaches, outlined in the next Learning Zone article. Files from the two methods offer somewhat different data availability and may be suited for different building performance simulation purposes.

PCIC’s dataset includes climate change-adjusted dry bulb temperature, dew point temperature, relative humidity, and surface pressure for a high emissions scenario, for three time periods: 2020s (2011 to 2040), 2050s (2041 to 2070), 2080s (2071 to 2100). Here, historical CWEC weather files are adjusted or “morphed” using the results from climate model projections. The PCIC dataset makes use of results from multi-model ensembles to address climate uncertainty.

On the other hand, NRC used a regional climate model (CanRCM4 LE) output to create eight weather files that include a baseline file (1991 to 2021) – produced from the modelled historical data, and seven future files representing different levels of global warming, from +0.5°C to +3.5°C. NRC’s dataset also provides the corresponding time-periods for each global warming levels: 2003–2033, 2014–2044, 2024–2054, 2034–2064, 2042–2072, 2051–2081, and 2064–2094. NRC applied the same TMY method used to create the CWEC files to produce future weather files. In addition to the TMY files, Moisture Reference Year, as well as Extreme Cold and Warm Year are provided for hygrothermal – heat and moisture – simulation and designing for extreme conditions.

Guidance on the use of these two future weather file datasets

Table 1 summarizes the data from the two different datasets, providing a comparison of key metrics. The table includes information on variables that were climate change-adjusted, time period of the future weather files, as well as the types of weather data made available for use in building performance simulation. The following bullet points offer direction to aid users in determining the most suitable dataset for their needs:

If one or more of dry bulb temperature, dew point temperature, relative humidity, or pressure are most important in your building design, you may want to consider using PCIC’s future weather files.
In the case of temperature, a statistical downscaling method (known as BCCAQv2) was used by PCIC to ensure that projected changes reflect local climate effects. They also used an ensemble of projections from the Canadian Downscaled Climate Scenarios (CanDCS), ensuring that the future climate change applied is not specific to a particular climate model.
If you are simulating a naturally ventilated building or are interested in solar radiation, you may want to consider using the NRC files that also have future hourly projections for solar radiation, wind speed/direction, and cloud cover.
NRC’s future weather file includes projections for variables such as solar radiation, cloud cover, as well as wind speed and direction that are not available for PCIC’s future weather files.
If you are concerned about peak energy loads or overheating, consider using both the TMY and “extreme” future weather files (Cold and Warm Year) produced by NRC.
To assess hygrothermal behaviour of the building assembly using simulation tools, you may want to consider using “Conditioning and Extreme Moisture Reference Year” files produced by NRC, as they include projected rainfall values.
In the case where weather files for your location are not available, you can always contact the Canadian Centre for Climate Services Support Desk for guidance.

Given the rapid evolution of climate science and services, it is expected that there will be future advancements in producing future weather files. As a result, building designers may want to periodically check for updates. We also recommend checking for updated versions of CWEC files as they become available too.

If you are interested in background information on weather files, how they are developed, and learn more about the methods used to produce each set of future weather files, refer to the ‘An In-Depth Look at Weather Files’ article.

Table 1. Summary of the two sets of future weather files developed by PCIC and NRC.

	Future Weather Files
	PCIC	NRC
Variables Adjusted	Dry Bulb Temperature Dew Point Temperature Relative Humidity Surface pressure	Global Horizontal Irradiance Direct Normal Irradiance Diffused Horizontal Irradiance Total Cloud Cover Rainfall Wind Speed Wind Direction Relative Humidity Dry Bulb Temperature Dew Point Temperature Surface Pressure Snow-Cover Flag
Emission Scenario	RCP8.5	RCP8.5
Time Periods	2011 to 2040 (2020s) 2041 to 2070 (2050s) 2071 to 2100 (2080s)	Present (1991 to 2021) +0.5°C (2003 to 2033) +1.0°C (2014 to 2044) +1.5°C (2024 to 2054) +2.0°C (2034 to 2064) +2.5°C (2042 to 2072) +3.0°C (2051 to 2081) +3.5°C (2064 to 2094)
Type of Weather Data	Typical Meteorological Year (TMY)	Typical Meteorological Year (TMY) Typical Downscaled Year (TDY) Extreme Cold Year (ECY) Extreme Warm Year (EWY) Conditioning and Extreme Moisture Reference Year (MRY)
Downscaling & Bias Adjustment	Statistical BCCAQv2	Dynamical QDM & MBCn
Model Projections	Ensemble of 10 climate models	Version 4 of the Canadian Regional Climate Model Large Ensemble (CanRCM4 LE)
Technique used for creating TMY	Morphing technique	TMY method

References

1. BC Housing. 2022. Extreme Heat and Buildings: An Analysis of the 2021 Heat Dome Related Deaths in Community Housing in British Columbia. Retrieved from: Extreme Heat Report 2022 (bchousing.org)