Thermal sensitivity and adaptive comfort in mixed-mode office buildings in humid subtropical climate

This study evaluates thermal sensitivity, expectations, and adaptability in mixed-mode ventilated buildings by subjective and objective assessments. A field study of simultaneous measurements of physical environmental parameters and right-here-right-now surveys was conducted in three office buildings from summer to winter in humid subtropical climates. The study confirmed previous findings that thermal adaptability and preferences changes as the ventilation system switches between natural ventilation (NV) and air-conditioning (AC). Occupants in this study showed more sensitivity to temperature changes than previously reported by ASHRAE Standards, yet thermal sensitivity was the same under different modes of operation. The neutral temperature was 0.5 oC higher than the predicted neutral temperature by ASHRAE 55 under both modes of operation. Thermal expectations were 1.5 oC warmer than the neutral temperature estimated by ASHRAE 55 when the building was operated by AC, while thermal expectations were almost the same as predicted by ASHRAE 55 under NV mode. Thermal comfort range was 0.75 oC wider than those predicted by ASHRAE 55 under NV operation, and the same as ASHRAE 55 under AC operation. The findings of this research provide a better understanding of mixed-mode building operations and perspectives from occupants, important for building designers and building operation managers.