Occupant centric controls (OCC) is a key approach to smart buildings. Gathering adaptive control parameters, such as occupant or environmental data, to improve occupant comfort, energy efficiency, and other smart building objectives. The industry understands the need for OCC but numerous research studies in the past year have highlighted the fact that there have been very few real-world OCC implementations, and that means a lot of unanswered questions.
“We scanned the literature for relevant work that has been done on this topic and analyzed its different attributes in detail,” says Ouf, an assistant professor in the Department of Building, Civil and Environmental Engineering at the Gina Cody School of Engineering and Computer Science, and co-author of a critical review of field implementations of OCC . “We realized that very few researchers have been able to actually implement these control approaches in real buildings for many logistical reasons.”
The research team, led by June Young Park at the University of Texas at Austin and colleagues at Carleton University, ETH Zürich and the University of Southern Denmark, identified 120 publications on the topic but only 42 studies included any kind of field implementation. Most of the research is made up of conceptual studies or simulations. All of them skewed toward North American or European standards, and only focusing on academic or office buildings. Despite the maturity of the smart building controls discussion, OCC is still very young.
“This whole niche of occupant-centric controls is still very new and provides exciting opportunities to combine advancements in data science and artificial intelligence with building engineering,” says Ouf. However, “the field’s newness means there is still no agreed-upon definition of what the term even means. Does the control approach prioritize occupancy patterns? Or does it focus on occupant behavior and their interactions with building systems? How much physical control should an occupant have in an automated building? Which metrics — comfort or energy efficiency — are prioritized, if either?”
Energy efficiency is usually the more straightforward of the two to study, quantify, and make a case for. Compared to comfort and other human-centric metrics, energy efficiency offers a clearer cause and effect relationships. Energy management in buildings involves many predictable mechanical elements but cannot be separated from the human-occupants it balances efficiency against. A purely efficient building does not even turn on lighting, HVAC systems, or anything else. The only reason we use power in buildings is for occupants.
“Building energy management is identified as a key part of the move towards localized energy generation and control. The significant discrepancy between building energy use as designed and during actual operation shows a need to evaluate the relationship between building occupants and energy requirements,” states a 2018 study by Sophie Naylor et al. “The need to better account for the influence of occupants on building energy use has been established through post-occupancy studies, highlighting the characteristics needed for more successful building control systems.”
While energy efficiency is a key part of smart buildings, the core purpose of a smart building is to serve its occupants. Smart buildings should be designed around creating an environment that suits the activity of the occupants of that building, be that work, play, healing, or learning. From that point, buildings can then find the most efficient way to manage energy use. One March 2019 study, by Da Li of the University of Michigan, et al, proposes an integrated Motivation-Opportunity-Ability (MOA) framework which incorporates social-psychological constructs from the Norm Activation Model and the Theory of Planned Behavior to investigate the determinants of energy-saving behaviors in the office environment.
“Occupant behavior has a significant impact on building energy consumption. To reduce energy use in office buildings, various intervention strategies have been investigated to promote energy-saving behaviors among occupants. However, the influential factors of these behaviors have not been fully understood in existing studies,” explains the paper. “Results of the structural equation model (n = 612) show that opportunity has the strongest effect on energy-saving behaviors, followed by motivation and ability. In addition, motivation mediates the effect of opportunity and ability.”
The young field of OCC is maturing towards standardization through these various research projects. In March, the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) released a new Handbook—HVAC Applications, which included a new chapter on ‘Occupant-Centric Sensing and Controls.’ Chapter 65 provides a technical overview of occupant-centric sensing and control as well as supporting data collection and modeling approaches. It focuses primarily on HVAC-related controls in buildings with automatic building management systems (BMS), where zone temperature is set based on real-time occupancy and/or comfort measurements.
“In many cases, such control schemes also incorporate predictions about future occupancy and/or comfort states. Previous applications demonstrate that such occupant-centric HVAC control schemes have significant energy savings potential of 10-40% and are able to maintain or improve occupant comfort outcomes,” explains Tianzhen Hong of the Lawrence Berkley National Laboratory, et al, in a study of the new ASHRAE chapter.
This growing body of research is making it clear that energy efficiency and occupant comfort are inseparable in the smart building context. Buildings are only there as a place designed to support occupant activities, as a roof to sleep under or as a safe and productive place to work, for example. Energy efficiency is the opportunity to reduce power consumption around those occupant-centric goals. OCC is a key approach to smart buildings that can balance these various demands and take us a step closer to smart, comfortable, efficient buildings.