Abstract
Nowadays different indices are used for the assessment of the visual discomfort related to glare, such as Daylight Glare Index, Daylight Glare Probability, and Vertical Eye illuminance. Regardless of their effectiveness in detecting glare perception, all these indices are intended to be local and instantaneous, not summarizing the long term glare perception through the space (Carlucci et al. 2015). In this work, a set of metrics able to express both the time constancy, i.e. availability, and the spatial uniformity, i.e. usability, has been used for detecting discrepancies and inconsistencies between the glare indices when dealing with time and space distribution. Results confirm that different glare indices can lead to different conclusions not only when considering point and instantaneous values but also when analysing availability and usability. Moreover, the availability and usability representations, indirectly confirm themselves effective in providing a global assessment of the confined space analysed, even when visual comfort is concerned.