Inter-Individual Variability of Human Thermoregulation: Towards Personalized Ergonomics of the Indoor Thermal Environment

Indoor temperature maintenance represents a large portion of the energy used in buildings and reducing dependence on energy-intensive thermal conditioning systems would benefit our fight against climate change as well as potentially have positive effects on human physiology/psychology. Thus, instead of conditioning spaces, the shift towards targeted conditioning of people is necessary. New technologies can now assimilate various inputs into building thermal controls with the potential to directly integrate physiological parameters from individuals living/working in the buildings. Yet the data to adequately model metabolic rate in individuals under various normal daily activities is still lacking. It is within this context that a synergistic collaborative effort between the Laboratory of Integrated Comfort Engineering (ICE) headed by Dr. Khovalyg at the EPFL and the Laboratory of Energetics and Advanced Nutrition (LEAN) headed by Dr. Ravussin at the UNIFR has been undertaken to try to integrate human physiology with building HVAC systems. The synergism between these two labs will take advantage of the ICE research facility in which the indoor environment can be controlled in a modular manner all while obtaining metabolic, physiological, and psychological data from subjects undertaking normal living/working tasks. In the first round of experiments, we examined physiological (e.g. metabolic rate, heart rate) and psychological (e.g. alertness, cognitive performance) changes during multiple normal day activities (e.g., standing up, eating a meal, low-level activity) in a “normal” population at thermoneutrality (23-24oC), cold (16oC), and warm (32oC) temperatures both during the summer and winter seasons (Khovalyg & Ravussin, Obesity, in press). Large interindividual differences amongst the subjects are demonstrated on multiple measured parameters and suggest that these differences will need to be integrated as input into future personalized temperature control systems. The second round of experiments is more office-centric and includes similar measurements while doing sitting work (typing), and standing work, while the meal is standardized. We will present our data related to these studies in terms of inter-individual variability of the metabolic rate and further overview metabolic rate models available from the literature and discuss their drawbacks when it comes to individuals’ dynamic metabolism. In addition, we will present our future outlook on how to capture humans’ dynamic metabolism using invasive and non-invasive approaches and use them to decrease the operational energy of buildings and potentially positively impact human metabolic health parameters (e.g. by impacting brown adipose tissue or creating thermal environments more conducive to higher mental concentration levels).