Most thermal comfort standards and guidelines currently in use do not consider occupants' adaptive capabilities associated with real-world situations when predicting occupant thermal comfort in mechanically conditioned buildings, although the adaptive approach is commonly applied to naturally ventilated buildings. These standards are generally based on results derived from experiments conducted in climate-controlled chambers. In some cases, this can lead to overcooling of buildings while still not satisfying most of occupants. One common method to reduce peak electricity demand is via temporarily increasing cooling temperature setpoint during peak hours. However, the potential negative impacts on occupant thermal comfort and wellbeing calls for further study on this. This paper describes a study conducted on a university campus in the United States that investigated occupants' thermal sensation, acceptability, and preferences corresponding to increased cooling temperature setpoint in parts of the building that are temporarily occupied. The results revealed a potential for at least temporarily increasing cooling temperature setpoint (at least 2 °C) across this campus without impairing occupant thermal comfort. For operative temperatures between 22 and 24.5 °C, the average Actual Mean Vote (AMV) for the class sections remained in the ASHRAE comfort range and the self-reported thermal acceptability was above 80%. Occupants’ thermal acceptability dropped to less than 80% when the temperature was increased to more than 24.5 °C, and the AMV values increased to more than 0.5 (on ASHRAE 7-point scale). The percentage of occupants who were involved in some sort of adaptive behavior did not considerably change with room temperature. •By temporarily increasing indoor operative temperature in campus classrooms from 21 to 25 °C, thermal acceptability remains above 80%.•At 23.5 °C, occupants' mean thermal preference and their actual mean votes equals zero, while thermal acceptability is above 90%.•Occupants' adaptive behavior in this study, with limited adaptive options, is not a function of the operative temperature.•Heat balance model under-predicts the percentage of dissatisfied occupants at environmental conditions warmer than neutral.