Evaluation and optimization of annual light variations for visual and non-visual effects within a ground-floor middle school classroom

The quality of the luminous environment in classrooms significantly impacts the performance, physical and psychological health of teenagers. This study proposes an emerging framework and improves the metrics to concurrently evaluate the visual and non-visual effects of annual lighting performance within Chinese classrooms. The year-round spatial and temporal variations of horizontal (desk) illuminance and vertical (eye-level) melanopic Equivalent Daylight Illuminance (mel-EDI) in ground-floor classrooms in Suzhou were evaluated using the latest Lark v2 lighting simulation tool. The Chinese Standard and WELL Building Standard were used to evaluate the compliance degree of static and dynamic metrics in the classroom under two conditions: daylightonly (all blinds open) and actual use (with blinds and electric lighting). In daylight-only conditions, the middle and south areas did not meet the visual requirements (>= 450 lx desk illuminance for >= 4 h) and the middle, south and front areas provided insufficient non-visual/circadian stimulation (>= 250 lx mel-EDI at eye-level for >= 4 h). In actual use conditions the insufficiencies were even more severe due to the use of low-transmittance blinds and glazing and inappropriate electric lighting configurations. Based on an evaluation of 27 (day)lighting scenarios, glazing transmittance of 0.78 and blinds transmittance of 0.5 were recommended. Additionally, electric lighting configurations were recommended to choose direct luminaires with luminous flux below 4000 lm or bidirectional luminaires of 3500-5000 lm to meet the visual and non-visual requirements of users, while also securing visual comfort and energy conservation within a reasonable range. The results of the study can be applied to secure adequate visual and non-visual stimulation within typical classrooms in Suzhou and other cities of East China that share similar climatic characteristics and educational building types.