Designing for future thermal comfort
It is important to keep in mind that although buildings may meet thermal comfort demands today, they may not be thermally comfortable in the near future. Due to global warming, outdoor temperatures have been increasing, and this trend can be expected to continue. This is concerning because overheating in buildings can result in dangerous conditions for occupants. Prolonged exposure to temperatures above 26 C (79 F) can increase risk of premature mortality and emergency medical service calls (Read “Towards establishing evidence-based guidelines on maximum indoor temperatures during hot weather in temperate continental climates” by Glen P. Kenny, Andreas D. Flouris, Abderrahmane Yagouti, and Sean R. Notley (2019)).
Considering the effects of global warming, it is imperative buildings are designed with future climatic conditions in mind. However, how does one design for unknown conditions? Currently, energy modelling guidelines require the use of Canadian Weather year for Energy Calculation (CWEC) 2016 weather file, which takes 12 ‘typical’ meteorological months selected from a database of 30 years. Past weather files are not a good guide for a rapidly changing future. Fortunately, groups such as the Pacific Climate Impacts Consortium (PCIC) are developing future weather-shifted data representing potential scenarios. Nationally, future climate files are being developed for the National Building Code (NBC), and requirements may be included as early as 2025.
Although future weather files will give a better indication of what design features will be necessary to avoid overheating, there are still limitations. Future weather files are based on ‘average-year’ CWEC data, and, therefore, will not account for extreme weather events. Global warming will result in a wider range of conditions than before. Therefore, it is essential to design buildings with passive systems that have been proven to increase resilience to extreme temperatures.
With the uncertainty of future climatic conditions and the limitations of weather files, it important to design for worst-case scenarios so that if overheating occurs, systems capable of combating harsh conditions are in place. By implementing both passive and mechanical strategies, it is less likely temperatures will exceed thermal comfort acceptability limits, even in hotter and more extreme conditions.
Thermal modelling analysis is under-utilized in the building industry despite the importance of thermal comfort for the health and productivity of occupants. Without further analysis and design alterations, it is unrealistic to expect a building to deliver thermally satisfying conditions for the majority of occupants. Thermal comfort modelling and analysis is the approach to optimize the design of a building for the satisfaction of future occupants while conserving energy and minimizing expenses. After all, buildings are nothing if not for the people who live and work within them.
Marc Trudeau, P.Eng., Architect AIBC, BEMP, CPHD, LEED AP, is the principal and team lead for building performance modelling at AME Group. He enjoys participating in projects to establish strategies for energy, greenhouse gas, thermal comfort, and sustainability performance. Trudeau can be reached at firstname.lastname@example.org.
Madeleine Lunde, EIT, LEED GA, is a building performance engineer at AME Group. She focuses on achieving energy and sustainability targets for buildings through energy modelling. She can be reached via e-mail at email@example.com.