Passive cooling strategies were implemented in 11 school buildings in Barcelona within a pilot project to improve thermal conditions. The present study aimed to evaluate the intervention's impact on students' comfort and wellbeing at school. A quasi-experimental pre-post study based on mixed methods was conducted. Quantitative data were collected through self-reported questionnaires administrated to sixth-grade students in 21 schools (11 in an intervention group, IG, and 10 in a comparison group, CG). The authors measured changes in satisfaction with indoor temperature and indoor air quality (IAQ), the presence of bothering factors (temperature too high, temperature too low, unpleasant odours, and lighting problems), and students' well-being and performance. Difference-in-difference analysis was conducted to evaluate differences between the IG and CG in pre-post changes. Qualitative data were collected through photovoice-based sessions (59 sixth grade students) and interviews (7 teachers) in the IG. A thematic content analysis identified three main categories: changes in perceptions of indoor environmental conditions, indoor environment-related health and well-being, and indoor environment and their reported impact on learning. Quantitative findings show positive changes among the IG in perceived indoor temperature, air quality, and well-being at school, while suggest no significant changes in perceptions of temperature too low, lighting problems, and students' performance, in relation to the CG. Compared to the CG, students in the IG perceiving temperature too high significantly decreased among girls, while unpleasant odours decreased only among boys. In the qualitative assessment, participants reported that school transformations improved their indoor thermal and visual comfort, IAQ, and unpleasant odours. Participants also reported a reduction of fatigue, stress, irritability, and stifling sensation, as well as enhanced concentration. This study highlights the benefits of school passive design for student's comfort and well-being in Mediterranean climates and suggests the need to extend these interventions to other school buildings in similar contexts.
