Adaptive resilience of indoor thermal comfort in a mixed-mode office: An assessment under anomalous climatic conditions

Climate anomalies linked to a changing climate increasingly challenge buildings to maintain comfortable indoor environments without excessive energy use. This study assessed physiological, behavioral, and perceptual responses of occupants in a mixed-mode office during an anomalous year in a subtropical region, which caused hotter-than-average conditions in typically mild seasons. In a year-long living-lab experiment, indoor environmental variables, HVAC use, clothing insulation, thermal perceptions, and physiological signals of 21 participants (12 females, 9 males) were monitored to examine adaptations to these anomalous conditions. Hotter-than-average days elicited higher mean and localized skin temperatures, particularly during outdoor exposure during lunch breaks. Occupants also adopted behavioral strategies, mainly reducing clothing insulation and adjusting building systems to reach higher air velocity levels. Indoor thermal perceptions varied under hotter outdoor conditions; however, the magnitude of this shift depended on the analytical direction adopted in the regression modeling. When thermal sensation was treated as the response variable to indoor conditions, the analysis indicated a notable reduction in neutral SET (-1.12 °C) during hotter days, whereas treating indoor conditions as the response to thermal sensation resulted in a minimal shift (+0.12 °C). Overall, the findings suggest that buildings can maintain comfortable conditions under climate anomalies when occupants are provided with meaningful adaptive opportunities. Incorporating building interfaces that enable adaptive opportunities, promoting flexible clothing adjustments, and applying adaptive comfort principles are essential for enhancing both building and human resilience in a warming and increasingly variable climate.