Balancing thermal comfort and energy efficiency through comparative HVAC setpoint strategies: Evidence from a field experiment in an SME office building

This study investigates the relationship between HVAC operational strategies, thermal comfort, and energy performance through a field experiment conducted in a small and medium-sized enterprise (SME) office building in Tokyo during summer. Four HVAC operational patterns were implemented on two office floors with fixed-desk and free-address layouts. Indoor environmental conditions and mean HVAC power demand were monitored. Thermal comfort was evaluated using the Predicted Mean Vote (PMV) model, and thermal dissatisfaction was defined as the proportion of measurements where |PMV| exceeded 0.5. The results showed that the existing uniform 24 °C baseline operation, which represented the prevailing HVAC operation prior to the experiment, produced overcooling conditions characterised by negative PMV values and elevated thermal discomfort rates. Modified operational patterns shifted PMV values closer to the thermal comfort range and generally reduced thermal discomfort compared with the baseline condition. Statistical analyses identified significant differences in PMV across operational patterns. Variations in mean HVAC power demand were also observed; however, these differences were not statistically significant. The fixed-desk office environment exhibited more stable thermal comfort improvements, whereas the free-address workspace showed greater spatial variability associated with occupancy distribution. These findings suggest that practical HVAC operational adjustments, including temperature setpoint revision and spatial zoning, can improve thermal comfort while maintaining comparable mean HVAC power demand under the monitored conditions.