Analysis of cloud distribution effect on daylighting in urban environment

The optimization of natural light is an important criterion for sustainable building in order to reduce the energy consumption due to artificial illumination. This article tackles this problem by using a simple urban case to simulate natural lighting. The main goal is to identify those parameters affecting interior daylighting. The case studied consists in a room oriented north, facing an infinite-wall across a street under an isotropic sky corrected with monthly cloud distribution of two locations at the same latitude. The computation was made using the radiosity method to determine the illuminance inside the room taking into account the sky diffuse radiation and all surfaces reflections. Results of daylighting inside the room were calculated for two values of the exterior wall coefficient of reflection. Preliminary results show that the urban color tend to influence greatly the inner illuminance, and slightly the daily number of hours with a standard visual comfort.