The National Research Council (NRC) is currently conducting research to generate information for the development of guidelines to address overheating in buildings arising from extreme heat events as may occur from a changing climate. Such events put the health of vulnerable populations such as the elderly, the sick and the young at risk. This information produced by the NRC will help building designers and practitioners implement revised design approaches where building mass, appropriate insulation levels and types of windows, as well as the choice of shading devices will all be considered as possible measures to prevent overheating of interior spaces during extreme heat events.
Given few studies have been completed that describe approaches to evaluate the effects of overheating on the comfort and health of building occupants, the NRC undertook a comprehensive review of this topic. As part of this work, a methodology was developed to generate reference years based on historical weather data to analyse the risk of overheating of building occupants. The methodology is based on changes in the heat stress index – which is an index of occupant comfort to surrounding temperature and relative humidity conditions of building occupants that accounts for local environmental conditions in proximity to a building (i.e. temperature, relative humidity, wind speed and solar radiation) as well as the amount of clothing worn, and the activity level of occupants. Through this, the NRC generated three types of reference years: extremely long, extremely severe, and extremely intense.
The NRC then analyzed the risk of overheating resulting in heat-related health effects on building occupants using these three reference years during shorter or longer periods of exposure to extreme heat events. Afterwards the NRC applied the methodology to a Canadian city and compared the methodology with existing temperature-based approaches to generate reference years. The results determine that using average weather years, as is typically done for completing building-energy simulations is not suitable for overheating analysis.
Christopher Pezoulas, Business Advisor