Addressing urban climate hazard vulnerability in Canada through building retrofit techniques and strategies

Abstract

The rapid growth of urban centers in Canada has highlighted the need for cities to improve urban resiliency to better protect the health and comfort of its residents. A key component of urban resiliency is a city’s ability to maintain occupant safety and comfort in the face of adverse climate hazards due to climate change. For many Canadian cities, the increasing prevalence of higher-than-average summer seasonal temperatures and dry conditions have led to intense wildfire seasons and the increased frequency of heatwave conditions. In response to these climate hazards, this study explored the use of building retrofit strategies to mitigate and reduce the severity of climate hazards' impacts on indoor environmental quality. To address indoor air quality challenges associated with wildfire events, this study explored the effectiveness and feasibility of wildfire-resilient mechanical ventilation systems to maintain acceptable IAQ in single-detached residences in western Canada. Outdoor PM2.5 concentration datasets during wildfire conditions were used in conjunction with IAQ mathematical models to assess the impact of ventilation and building-related input variables on indoor PM2.5 levels. A cost-benefit analysis was conducted to compare the cost of ventilation retrofit options with regional estimates of reasonable monetary contributions per resident toward health risk mitigation. Ventilation retrofit options were recommended based on IAQ simulations, model sensitivity, and cost-benefit analysis results. It was recommended that residential ventilation systems increase the minimum filter efficiency from MERV6 to MERV11 or MERV13 during wildfire operation and implement higher recirculation ratios during peak exposure scenarios. Multi-filter mechanical ventilation system configurations were recommended for residential dwellings located in regions prone to severe PM2.5 exposure. This study provides insight into the integration of wildfire resiliency in existing residential mechanical ventilation systems for IAQ improvement. This study sets the foundation for future experimental verification of the performance of ventilation strategies to improve urban safety, health and wellness during the wildfire season. To mitigate the impact of heatwave conditions on the indoor space and maintain indoor thermal comfort, this study focused on the optimization of automated shading systems to maintain indoor thermal conditions during both the heating and cooling seasons. Preliminary building energy modelling was used to develop a cold-climate optimized sensorless control strategy for automated roller shades. A mathematical model was developed to estimate shading system energy performance based on user-defined building specifications and weather-related variables. The effectiveness of the automated roller shading system as a green retrofit technology was explored by comparing season-specific energy savings and payback periods for various cold climate zones. A field study quantified the impact of roller shade operation on indoor thermal conditions. The technology exhibited a payback period range of approximately 5 – 15 years, depending on factors such as glazing type, orientation, solar exposure, and local climate conditions. Findings from both the simulation and prototype field study support the use of cold climate-optimized automated shading systems as a year-round green retrofit strategy for buildings. This study serves as a pioneering effort and justification for cold climate zone buildings to implement retrofit technologies for improved indoor thermal control during heatwave conditions while ensuring year-round technology functionality. Overall, wildfire-resilient mechanical ventilation and cold climate-optimized automated shading are effective strategies for maintaining IAQ and indoor thermal comfort within the built environment. The implementation of these technologies can improve climate change resiliency within the built environment while ensuring comfortable indoor conditions for all occupants.