A comparative study between Daylight Factor Based Metric and other Daylight Metrics for Daylighting Design

The calculation of the daylight illuminance for a given position in a building is a key step in daylighting schemes. In order to predict the daylight performance of room space and set a scale for architects to use when comparing aspects of various daylighting schemes, there are a number of rules of thumb and design metrics. The Daylight Factor based metric is under the traditional overcast sky excluding direct sunlight. It is frequently formalized within national standards in many countries. However, such metric does not consider the dynamic variations in daylight illuminance. Recently, daylight factor calculations have been extended for all sky conditions. It means that Daylight Factor based metric is no longer static and it can take into account the building directions, solar positions and the effects of direct and reflected sunlight. This paper provides a review of the daylight factor based metric and gives an overview of the current dynamic daylight metrics. The daylight factor based metric and other dynamic daylight metrics are analysed. The findings would be useful to practitioners engaged in visual comfort, fenestration and daylighting design and evaluation.