Fan cooling as an effective strategy to enhance thermal comfort and energy efficiency for short-term supine rest

• Optimal condition for supine rest is 29 °C with 0.4 m/s airflow in this study. • Fan cooling saves 25.3 % energy and outperforms HVAC in comfort. • Air temperature and air speed significantly affect distal skin temperature. • Fan cooling is more effective at lower ambient temperatures. Short-term supine rest commonly occurs in settings such as airport rest pods, midday breaks, and hospital wards, where conventional air-conditioning often struggles to provide efficient comfort. Fan-based personal comfort systems offer a practical solution, but findings from seated postures cannot be directly generalized to supine rest due to differences in thermoregulation and heat transfer. This study aimed to determine optimal fan conditions and clarify the physiological basis of comfort during short-term supine rest. A two-factorial experiment with 14 healthy adults tested nine combinations of air temperature (26, 29, 31 °C) and air speed (0, 0.4, 0.8 m/s). Local skin temperatures and subjective thermal perception votes were collected over 40 min. The results showed that 29 °C with 0.4 m/s airflow was the optimal condition, yielding the highest comfort and reducing HVAC energy use by 25.3 % compared with 26 °C without airflow. Both air temperature and airflow significantly influenced thermal perception and local skin temperatures, with distal body sites showing greater sensitivity to the thermal environment. Interaction effects indicated that airflow alleviated heat discomfort, but its cooling benefit diminished as air temperature increased. Overall, this study provides empirical evidence that fan cooling can enhance thermal comfort and energy efficiency in short-term supine rest, offering valuable guidance for future design standards.