Exploring Impacts of Thermal and Lighting Conditions on Office Workers’ Subjective Evaluations, Cognitive Performance and EEG Features in Multi-Person Offices

Modern office workers spend lots of time in multi-person offices. For human-centered building design and operation, it is essential to investigate the influence of coupled physical environments on occupants' well-being and task performance. In this study, to assess impacts of thermal and lighting environments on brainworkers, experiments were conducted under 64 conditions of different temperature, correlated color temperature, and illumination in a multi-person office. Electroencephalogram (EEG) signals were collected to measure the mental state of brainworkers and neurobehavioral tests were utilized to replicate cognitive tasks. The results indicated that only the interaction between the temperature and illumination regarding the sensation of CCT was significant. Primarily, lower illumination in colder environments made subjects perceive the lighting was warmer. Furthermore, cross-domain effects influenced office workers' sensation via synesthetic effects. And the validity of the hue-heat hypothesis on thermal sensation depended on whether subjects received enough stimulation. Besides, for brainworkers, visual comfort peaked at 5000 K and 750 lux but the optimal temperature varied based on specific requirements, with 24 °C promoting overall comfort and 26 °C enhancing executive cognitive performance. The study preliminarily explored the effects among acceptable levels of T, CCT, and I on EEG features, revealing that temperature could adjust occupants’ mental load. However, the further investigation requests equipment with finer temporal granularity, cost-effective techniques and advanced analytical methods to guide office building design and operation.