Dynamic cooling: Thermal and temporal effects on cognitive load and performance in office environments

• Thermal and temporal effects of dynamic and constant cooling conditions were tested. • Performance and cognitive load were collected over 7 h in hourly intervals. • No relationship between performance and air temperature could be established. • Thermal perception results indicate that 23 °C represents an overcooling of offices. • Daily trends in performance and fatigue are better in dynamic vs constant exposure. The integration of dynamic thermal environments, characterised by time-varying temperatures within a building, can contribute to increased energy flexibility and a reduction in overall energy consumption. Recent research indicates that exposure to varying temperatures has the potential to enhance worker performance and wellbeing. This study examined the time-dependent impacts of temperature exposure on cognitive load and performance. In a simulated real-world office environment, 36 participants were exposed to automated conditions, including a conventional constant temperature cooled (CC) condition of 23 °C and a dynamic cooled (DC) condition with a constant temperature of 26 °C in the morning and a temperature change of 1.5 °C/h after lunch, resulting in a temperature of 23 °C in the afternoon. In both conditions, performance tasks, mental workload, arousal and thermal perception questionnaires were conducted at hourly intervals throughout the working day, from 9:00 am to 4:00 pm. Results showed similar performance in both conditions with no direct relation to a set-point temperature. The analysis of the time of day revealed significant effects in both conditions. In the morning, participants rated feeling significantly more relaxed and thermally comfortable in the higher temperature in DC than in the lower temperature in CC. During the afternoon, an increase in self-reported fatigue was observed in the CC condition, which could be significantly mitigated by the dynamic condition. The findings of the study challenge the practice of maintaining constant temperatures in offices, underscoring the need to consider the impact of time of day variations on workers’ wellbeing.