A framework to characterise operational daylighting performance in classrooms: measurement, observation and user perspectives

Research confirms that daylight is important not only for vision, but also for general well-being. Little is known, however, about how real world occupied spaces perform in terms of daylight. This holds true particularly in schools, where practicalities prevent the collection of data from classrooms in use.

The framework presented here addresses the lack of daylighting performance evidence from the real world, necessary for guiding daylighting predictions for classroom design. It describes and prototypes a methodology that achieves long-term daylighting performance monitoring in classrooms in use. This methodology also enables the observation of actions the occupants take to sustain or improve their visual comfort.

Four UK secondary school classrooms were used as case studies and were monitored for up to a year. A mixed method approach was taken in order to associate measured luminance, a physical characteristic of light, to user interaction with electric lights and blinds, as well as student subjective responses.

This resulted in two novel fine-grained year-long datasets, as well as a record of student appraisals of the luminous environment. The luminance dataset contains over a trillion measurements captured on-site simultaneously for multiple (nearly 18,000,000) points in space, at a 10-minute frequency over a year, resulting in multiple (over 62,000) points in time.

Application of the long-term monitoring method was found to be robust and useful for monitoring complex multi-user spaces for at least six consecutive months. Combining fine-grained luminance mapping, records of occupant interactions with design elements and occupant subjective views of the case study classrooms provided a better understanding of the many factors that shape operational daylighting performance. This was achieved by identifying specific parameters, examining their effect across a set of the three types of evidence and highlighting the complex relationships detected between them.

The three aspect framework presented here contributes to a philosophy of research that addresses real world challenges by combining their technical, behavioural and subjective expressions. In doing so it supports the view that sustainable and thus effective solutions are those that stem from holistic people-centred interdisciplinary research.