Reality bites: measuring actual daylighting performance in classrooms

Climate-based daylight modelling (CBDM) is providing the basis for yearlong indoor daylighting performance predictions. However, evidence of long-term actual daylighting performance of indoor spaces in use is limited. Since 2013, CBDM has been a mandatory requirement for the approval of school designs that fall under the UK’s £6 billion Priority Schools Building Programme. Specifying daylight compliance of schools with CBDM metrics increases the urgency for evidence of actual performance of classrooms. This paper describes a method for long-term monitoring of classrooms in use. It also identifies the key confounding factors that make the validation of CBDM metrics in practice a daunting task. Two UK classrooms are used as case studies and are monitored daily for six months with a 10-minute resolution. Using a robust method, based on High Dynamic Range (HDR) imaging, this work makes a case for the significance of real world daylighting performance measurements. Moreover it provides an overview of the first steps toward the evaluation of the practical application of CBDM prediction methods and metrics.