Occupant Behaviour and Thermal Conditions in Small Commercial Buildings: A Longitudinal Study Using Smart Thermostat Data

The occupant response to thermal discomforts plays a significant role in uncertainties associated with modeling and implementing building energy performance measures. In particular, for managers of small commercial building portfolios, a better understanding of the occupants' interactions with the HVAC system is necessary for managing these uncertainties and reducing discrepancies between predicted and actual energy use. In Canada, these buildings are currently underserved by energy conservation and thermal analysis tools because of their dispersion and lower payback potential. Smart thermostats, along with their centralized data collection platform, provide an efficient and low- cost solution to collect massive amounts of data from a portfolio of these buildings that can be used to improve the understanding of the occupants' behaviours and preferred thermal conditions. This paper presents the results of a longitudinal study based on the smart thermostat data from a portfolio of more than 240 small commercial buildings located in Ontario, Canada. We analysed the occupant-thermostat interactions, as well as the HVAC setpoints adjusted by the portfolio manager, to answer two main questions: 1) what contextual factors are associated with the initializing of overrides in the portfolio of small commercial buildings, and 2) how do the thermal conditions managed by HVAC schedules (that are based on seasonality and occupants' feedback) and occupant overrides reflect industry-standard criteria; specifically PMV? The results can help the portfolio managers to better understand the users' interactions with the HVAC system under various circumstances and create efficient energy conservation programs while meeting the occupants' thermal preferences and organizational productivity.