Multiscale daylight modeling for urban environments

Daylight in buildings is the natural illumination experienced by the occupants of any man- made construction with openings to the outside. The quantity and quality of daylight in buildings is continually varying due to the natural changes in sun and sky conditions from one moment to the next. In urban settings, the dynamics of daylight illumination are ampli ed by the vertical extent of buildings and the density of the built form. Traditional schema for evaluating daylight in the built environment consider only one or perhaps a few `snapshot' conditions, e.g. a single overcast sky, or a sequence of shadow patterns for selected hours. This chapter describes the application of a technique called climate-based daylight modelling (CBDM) across various urban scales { from o ce spaces to large- scale city models. Climate-based daylight modelling is the prediction of various radiant or luminous quantities (e.g. irradiance, illuminance, radiance and luminance) using sun and sky conditions that are derived from standard meteorological datasets. Climate- based modelling delivers predictions of absolute quantities (e.g. illuminance) that are dependent both on the locale (i.e. geographically-speci c climate data is used) and the building orientation (i.e. the illumination e ect of the sun and non-overcast sky conditions are included), in addition to the building's composition and con guration. The examples described in this chapter include theoretical studies and two `live' projects.