Larger urban areas in the world experience rapid population growth. Even in highly urbanised areas in Europe this trend is noticeable. Brussels has a growth rate that is one of the highest in Europe and thus there is a strong need for extra surfaces to receive all activities including working, retail and leisure, but in particular for housing. As open space is scares in historical cities one option is to increase the density of the existing urban fabric. Higher densities are certainly a way towards more sustainable cities but there are limits that are specific for each case and climate. In very dense urban environments daylight at street level can be reduced dramatically due to multiple obstructions. This study focuses on daylighting aspects in an urban context. A methodology is proposed to estimate daylight for urban design, planning and policy purposes. The goal is to offer simple and yet efficient criteria for spatial planning, knowing that exact shape of buildings and properties of the facades are not known at this stage. The method is then applied to a high density development in Brussels where different massing arrangements are studies. The impact is investigated for each alternative and the improvements of a final amended proposal for the urban masses are checked.