Let there be daylight? Assessing actual daylighting performance of a classroom in use

Daylight is a non-depleting energy source with the potential to reduce building energy consumption and contribute to the health and wellbeing of building occupants. The increased reliance on daylight simulation tools, for the prediction of indoor daylighting performance, calls for sound benchmarking based on data from actual spaces in-use. However, due to practicalities such data are limited especially in the case of classrooms. The mixed method study presented here took a user-centred approach to investigate the relationship between three aspects of evidence collected from the real world: monitored illumination data; observed user interactions with the space and its systems (visual display technologies, electric lights, blinds); and user subjective responses. A UK classroom was used as a case study and was monitored for three months between September and December. High Dynamic Range (HDR) imaging was the technique used to provide (at a 10-minute interval) physical measurements of the luminous environment and data on the actions users took to maintain or improve visual comfort. A questionnaire (n=117) recorded the students’ subjective responses to the luminous environment. Findings from the combined study of these datasets lead to a deeper understanding of the occupants’ current visual needs and their perception of daylight, which is necessary for the development of realistic daylighting performance – and subsequently whole-building energy predictions.