The impact of changes in daylight illuminance levels on architectural experiences in office environments using virtual reality and electroencephalogram

This study investigates the influence of varying daylight illuminance levels on architectural experiences in a virtual office environment. Integrating subjective assessments and electroencephalogram (EEG) data, we aim to comprehensively understand how illuminance impacts emotional and neurophysiological responses. The experiment exposes participants to nine illuminance levels, ranging from 66 to 1500 lux, to discern optimal conditions for different architectural experiences. Subjective evaluations, gathered via questionnaires, required participants to rate the perceived pleasantness, interest, excitement, calmness, and spaciousness. Simultaneously, EEG data was recorded to analyze neurophysiological changes associated with different illuminance conditions. The results showed that the power of the alpha and theta band at channels in the parietal and centro-parietal regions had statistically significant differences under nine daylight illuminance levels. Illuminance changes activated brain regions associated with cognitive functions. The relative power of alpha band at the parietal region were negatively correlated with the subjective evaluation, and was relatively low at levels between 300 and 900 lux, indicative of heightened pleasantness, interest, spaciousness, with the peak experience occurring in the 700-900 lux range. Illuminance exceeding 1300 lux, conversely, correlated with increased absolute power of the alpha band, suggesting heightened arousal, while levels below 300 lux led to decreased arousal and increased calmness. By integrating neurophysiological measures with subjective evaluations, we gain a nuanced understanding of how illuminance affects emotional and cognitive responses. This research may provide a reference for the selection of office illuminance levels for employees during high- intensity mental work and rest.