MODELLING WEATHER FUTURES Weather – A Foundational Input The fundamental purpose of a building is to protect occupants from exterior conditions. Historically, this has meant designers – architects and engineers – look at typical climate conditions in the project’s location and develop building systems to meet these conditions. In the face of climate change, however, the industry has a new challenge: designing buildings that adapt to unknown future changes in the exterior environment, while providing occupants with thermal comfort and protection against today’s elements.
25 years old. These CWEC (Canadian Weather for Energy Calculations) files are available for free download from Environment Canada. Using Toronto, Ontario as an example location, Figure 1 shows that the historical heating degree day trend has shifted an entire ASHRAE climate zone over the past 60 years. This clearly illustrates that using a weather file representing the time period from 1959-89 no longer provides a valid representation of current climate conditions in Toronto. In 2016, Environment Canada released an update to its CWEC weather files. The new files, termed CWEC2016, represent typical climate conditions over the years 1998-2014 – a more appropriate approximation of Toronto’s current climatic conditions, as shown in Figure 1. While use of these new weather files is increasing, the industry can help spread adoption by requesting that CWEC2016 be used for all new building energy models.
By Mike Williams and Jennifer Harmer
Building energy simulations estimate the annual energy performance of a proposed building design under a given set of exterior climate conditions. These simulations use a set of input climate parameters known as a “weather file.” Results from these energy models can inform the design of heating, ventilation and air conditioning (HVAC) systems, or determine the effect of different design strategies on overall building performance. Intuition coupled with recent academic research suggests that selecting an appropriate weather file is perhaps the most important foundational input into any energy performance analysis. Despite this, the most commonly used weather files for buildings in Canada describe typical climate conditions between the years 1959-89 – data over FIGURE 1: ANNUAL HEATING DEGREE DAYS (BASE 18°C), TORONTO, ON 1953 - 2016.
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