Daylighting Metrics: Is there a relation between Useful Daylight Illuminance and Daylight Glare Probabilty?

The establishment of climate-based daylight modeling within research and practice has led to a fundamental reassessment of both the basis and purpose of daylight metrics. Whilst there is no consensus yet on the precise nature of the metric(s) that should replace the daylight factor, it is generally agreed that these should be founded on climate-based daylight modeling (CBDM). In this paper we examine the relation between the predicted annual occurrence of glare and one of the candidate CBDM metrics that has been proposed, called useful daylight illuminance (UDI). The purpose is to determine if one or more of the UDI metrics (predicted for the horizontal workplane) could serve as a proxy for the probability of daylight glare (i.e. a measure of vertical illuminance received at the eye). For glare we use the simplified daylight glare probability model. The setting is a residential building which we use as a ‘virtual laboratory’ in two design configurations, each evaluated under all 32 combinations of 8 European climates and 4 building orientations.