Comparative review of occupant-related energy aspects of the National Building Code of Canada

Given that human behavior is increasingly recognized to play an essential role in building energy use, the validity of occupant-related assumptions in the building code and in the energy performance modeling tools used for demonstrating code compliance is a central concern. This paper investigates the current occupant-related assumptions in the National Building Code (NBC) of Canada compared to new and emerging data sources, along with their potential energy and design impacts. Six parameters were selected: setpoint temperatures, domestic hot water (DHW) use, appliances lighting and plug (ALP) loads, internal heat gains, mechanical ventilation, and the number of occupants. For each parameter, available data sources were compared against the NBC assumptions. Our analysis indicates that several code assumptions are substantially different from findings in recent measurement-based studies. For the temperature setpoints, the mean heating and cooling setpoints are approximately 1.5 degrees C cooler than the current NBC specification (21 degrees C and 25 degrees C, respectively). For DHW, the total daily volume is highly dependent on the number of occupants; hence, the current assumption of NBC (225 L/day) may not reflect the typical current use. Moreover, the hourly schedule for DHW use specified by NBC is significantly different than all data sources found (primarily in the timing and magnitude of morning and evening peaks in usage). For internal heat gains, the available data suggests a similar profile as NBC, except for that absence of a morning peak. Therefore, the findings presented in this study illustrate a need for revising the current building standards/codes.