Impacts of personalized environmental control systems on human psychophysiological responses to outdoor-to-indoor transitions in summer

Personalized Environmental Control Systems (PECS) offer adaptive strategies to enhance occupants’ comfort while improving energy efficiency. These systems may support the restoration of thermal comfort after spatial transitions. This study investigates occupants' psychophysiological responses after outdoor-to-indoor transitions in Florianópolis, Brazil. The experiments were designed to mimic a typical office day, in which participants transition from outdoors in the morning upon arrival and after the lunch break. Participants underwent three experimental scenarios: using a small evaporative cooler, a desk fan, or no PECS. Conducted in a university living lab with a slightly elevated cooling setpoint (26 °C vs. the conventional 23 °C–24 °C), results showed higher usage of evaporative coolers (50.0 %–87.5 %) compared to desk fans (37.5 %–58.3 %). Both PECS effectively modified near-body thermal conditions, reducing wrist-level air temperature (evaporative coolers: 1.10 °C ± 1.88 °C; desk fans: 0.96 °C ± 1.18 °C, mean ± SD), with long-term effects. Mean skin temperature (MST) reductions were higher using evaporative coolers. However, statistical modeling confirmed that the use of both PECS impacts MST. While PECS did not alter descriptive thermal comfort indicators (e.g., thermal sensation) under neutral indoor conditions, they influenced hedonic responses such as thermal preference. This suggests that thermal PECS may help reduce the preference bias toward cooler thermal sensations, commonly observed in warm-to-hot regions. Since PECS also affected physiological signals, the shift in preference likely results from a combination of physiological changes and lowered expectations for cooling. Consequently, using PECS may support higher setpoint temperatures and contribute to energy savings in buildings.