Assessing self-perceived productivity from tangible aspects of indoor environmental quality (IEQ): A case study in university classrooms in a humid subtropical climate

Indoor environmental quality (IEQ) plays a crucial role in occupants’ well-being and daily performance. Understanding this relationship is important in educational buildings, as students spend significant time in classrooms. This study integrated environmental measurements – operative temperature, illuminance, CO 2 concentration and noise – with 972 student responses collected across 23 classrooms at a university in the humid subtropical climate of Southern Brazil. The dataset was structured into 100 classroom sessions and analysed using a combined framework of multiple linear regression, K-means clustering and discriminant analysis. The regression model explained 56% of the variance in perceived productivity, with temperature and illuminance showing positive associations and noise and CO 2 showing negative effects. Cluster analysis identified two statistically distinct profiles, with the higher-performing cluster exhibiting more favourable conditions, including higher operative temperature (23.23°C vs. 19.99°C), greater illuminance (326.76 vs. 231.60 lux), lower CO 2 concentration (993.73 vs. 1305.13 ppm), and reduced noise levels (53.74 vs. 57.19 dB). These differences corresponded to higher perceived productivity (48.71% vs. 46.63%), with a large effect size (Cohen's d = 0.79). Discriminant analysis achieved 96% cross-validated classification accuracy, supporting the robustness of the profiles. The findings demonstrate that distinct combinations of IEQ conditions produce measurable differences in perceived performance.