Enhancing daylighting predictions in urban planning: A workflow for setting bespoke Vertical Sky Component (VSC) targets

In Sweden, urban planners are legally obligated to design neighbourhoods that allow future buildings to meet daylight requirements. However, this is challenging because planners can only define the building masses, without control over future building details such as glazing ratios, room layouts, and orientation.The Vertical Sky Component (VSC) is a well-established indicator for early daylight assessments of buildings, and it is often used by Swedish urban planners to verify daylight access for their massing designs, even though it has its limitations. A VSC target value VSC ≥ 27 % has been widely applied in the urban planning practice. However, a single universal VSC target does not necessarily guarantee compliance with daylight requirements indoors. This article proposes a workflow for setting bespoke VSC targets. The goal is to provide urban planners with more reliable tools for early daylighting predictions. The workflow uses parametric simulations to establish VSC thresholds that assure compliance with current daylight regulations, such as the Swedish building code (BBR) and the European standard (EN 17037). While this article focuses on Sweden, the workflow could be readily applied to any location with prevalence of overcast sky conditions. Some potential practical urban planning applications of the workflow are suggested.