Long-term monitoring of indoor environmental quality, student comfort and contextual factors in four university classrooms

Indoor environmental quality (IEQ) in university classrooms affects student comfort and learning outcomes. Long-term monitoring of IEQ, student comfort, and contextual factors was performed in four identical recently built classrooms at Politecnico di Torino with different orientation, in spring 2023 and winter 2024. The thermal, acoustic, visual and indoor air quality (IAQ) parameters were monitored using wall-mounted multi-sensors, verified against reference instruments. Concurrently, students completed online questionnaires on comfort, while contextual conditions (door opening, solar shading, use of the voice reinforcement system, etc.) were recorded. The aim was to find the best predictive models of subjective outcomes from objectively monitored data with a long-term objective and subjective assessment system. This setup is expected to support rapid adjustments to maintain optimal conditions, improve occupant comfort, and reduce manual workload for facility managers. The results show that contextual factors are essential to interpret objective and subjective data. The questionnaires showed that in winter, the overall perceived IEQ was mainly influenced by thermal comfort, while in spring it was primarily influenced by indoor air quality, which were the least rated factors in each season. The objective indexes for thermal and acoustic quality showed the best agreement with subjective comfort. The acoustic model, which is based on the minimum level of speech required to achieve an optimal signal-to-noise ratio, requires a lower threshold under conditions of good room acoustics. The IAQ and visual models should account for the position of the sensors and their layout, whether vertical or horizontal.