It is clear that increasing urban density is a necessary strategy for cities as they move towards more sustainable futures. It should not be lost however that increasing density, if not done in an informed manner, can have catastrophic effects on daylight levels inside buildings. Daylight regulations at the building level afford a degree of protection for daylight, but an area’s zoning plan can often make compliance with such regulations difficult if not impossible from the start. Given that urban density is a particularly important determinant of daylight access, monitoring the effect of early stage planning decisions on daylight makes good sense.

Sweden presents an interesting case study, as over the past decade, a rapid increase in land prices has fueled a move towards increasingly densely planned settlements. The Swedish climate, with its dark winter months, has posed a formidable challenge however. The result has been that many recently planned settlements struggle to meet the code requirements for daylight. As a means of assessing the effects of early stage planning decisions on daylight, the metric Vertical Sky Component (VSC) has started to make its way into the planning process. Urban scale daylight modelling however is unfamiliar to most practitioners so, in an effort to establish a point of reference for this approach, a project was undertaken showing VSC results along with Floor Area Ratio (FAR) data for 40 existing urban districts. The basic idea is that planners can more easily understand and interpret results generated for new developments if they are able to compare their results with those for neighborhoods they are already familiar with.

In addition to presenting VSC and FAR results for the selected urban districts, this paper also addresses the inherent challenges and restrictions of introducing a new metric into an already complex planning process. The potential for introduction of climate based daylight metrics in the future for planning purposes is also discussed. Results show that, although urban density and VSC are clearly related, there are instances where a number of urban typologies clearly perform better than others. This suggests that urban daylight modeling does not necessarily restrict development but rather can function as a tool to optimize building form. Though somewhat outdated when compared with modern
climate based assessment methods, the Vertical Sky Component metric is conceptually simple, easy to calculate and, perhaps most importantly, relates closely to the methodologies of the current Swedish building code. As such, its use in the planning process should be considered a solid first step to protecting access to daylight.

Paul Rogers is an architect and Sustainability Coordinator at BAU Architects in Stockholm. A registered BREEAM assessor, he leads a division of three daylight specialists working with daylight certification of buildings. He is founder of the LinkedIn discussion forum ‘Svensk dagsljusberäkning’ (Swedish daylight calculation) which has nearly 300 members. Along with select members of this group, he is working to advance domestic daylight certification methodologies and to help Swedish Building code authorities modernize the country’s daylight regulations. He is also founder of an ongoing initiative which challenges Swedish urban planning authorities to better integrate daylight into municipal planning process.