How Does Building Occupancy Influence Energy Efficiency of HVAC Systems?

Occupancy (presence and number of occupants) is one of the most important factors impacting energy efficiency of HVAC systems as occupancy determines heating/cooling loads on the demand side by varying conditioning periods and settings. Despite the high volume of research activities in demand-driven HVAC controls, how and when occupancy should be linked with heating/cooling loads for sustained and maximum efficiency are still not clear as occupancy is stochastic in nature, and there exists heat transfer and balance among zones, as well as heat gain and loss through a building's envelope. There is no solution to date that can be directly applied in different buildings with different HVAC systems and occupancies. This paper systematically investigates how the occupancy influences the energy efficiency of HVAC systems. Specifically, the influence is analyzed from three perspectives of occupancy transitions, variations, and heterogeneity. The results demonstrated the energy significance of the three perspectives and provided the general ways of quantifying the influences of occupancy.