The effect of urban density on compliance with indoor visual and non-visual daylight targets: A Dutch case study

The high density of the urban fabric poses a real challenge for adequate daylight design in residential buildings. European and national building standards do not provide sufficient guidelines on if and how to consider the urban context at design stage. This study assessed the impact of simulating different urban densities on the indoor daylight performance of typical Dutch apartments. Results showed that not including the surrounding environment when designing a new building leads up to an 85% overestimation of daylight performance, causing an insufficient daylight provision for most apartments built at the lower floors. Furthermore, settling for daylight target values any lower than the minimum standards specified by EN17037 (median illuminance of 300 lx) will lead to insufficient melanopic light levels. In this regard, two new metrics are introduced to compare the non-visual performance between apartments: Melanopic Autonomy and Melanopic Isotropy. These metrics enable the characterisation of non-visual performance of an entire space, rather than of a single occupant position. Last, the analysis explored the relationship between indoor daylight performance and urban density indicators; while the results are limited to the sample considered in this study, a promising relation was noticed for the floor-space index and for the open-space ratio.