Occupant-centric experimental evaluation of fully tinted suspended particle device smart windows on thermal comfort in summer

Abstract

To enable the utilization and wider adoption of smart window technology, evaluation across multiple performance dimensions is required. However, studies on occupant comfort remain insufficient, and, in particular, the effects of smart window tinting on actual occupants remain underexplored. To address this knowledge gap, this study recruited sixteen participants and conducted experiments from July to August 2023 in rooms equipped with smart and conventional windows. Data were collected for indoor temperature and predicted mean vote (PMV), for occupants’ skin surface temperature, and for thermal sensation (TSV) and comfort (TCV), obtained from questionnaires. Perceived thermal comfort under full tinting was evaluated at two initial indoor temperatures without cooling, 26°C and 30°C. When the initial temperature was 26°C, dry-bulb, globe, and skin temperatures, PMV, and TSV in the smart window room were lower than in the conventional room, and their increases during occupancy were smaller. The differences in dry-bulb and globe temperatures, PMV, and TSV corresponded to effect sizes of at least 0.8, indicating a very large practical difference. When the initial temperature was 30°C, the same trend was observed with smaller magnitudes of increase. TCV was higher in the smart window room in all cases. Results were statistically significant for all analyses (p < 0.05), demonstrating that in summer full tinting of smart windows improves occupant thermal comfort both objectively and subjectively. These findings support the efficient operation of smart windows and the technological applicability of smart window technology toward the realization of sustainable built environments. © 2026 Elsevier Ltd