A Study of the Accuracy of Daylighting Simulation of Heavily Obstructed Buildings in the Urban Canyons of Athens

This paper deals with the use and evaluation of daylighting simulation tools in relation to a complex urban environment. The environment concerned is one commonly found in city centre areas where the proximity of buildings leads to the creation of ‘urban canyons’; the result of this is that assessment and simulation of daylight requires a more sophisticated approach than for other situations. In urban areas building layout is the most important factor effecting daylight, sunlight and solar heat gain reaching a building. It also affects sunlight in open spaces, ventilation, shelter and the dispersal of pollutants. In order to produce a more realistic understanding of the dynamic effects of daylight, there is a need not only for the research and development of advanced CAD and lighting simulation tools, but also of the study of possible alternative methods in their application. In the work reported in this paper, an attempt has been made to move the focus of lighting and daylighting simulation from the scale of a room to that of a whole building; the building itself being surrounded by its specific urban environment (including its microclimate). The study evaluates if there is sufficient evidence that it is possible with such complexity to reach reliable computation results after executing the simulation. The case study presented uses a 4D model of an urban canyon to investigate the sensitivity of such a complex simulation system. It can also be used to find ways to analyse and predict how daylight is reflected, refracted, scattered, diffused, polarised, diffracted and absorbed as it traverses an urban environment.