Prognose von Verschattungen im Umfeld komplexer Bebauung

Forecast of shadowing duration in urban regions.

Purchasing condominiums or houses, preparing land-use plans or with civil lawsuits in connection with new building projects more and more frequently predictions of shadowing are required. Concerning the assessment there are no binding definitions according to planning and building regulations law with regard to sufficient duration of sunlight. In practice an assessment of calculated duration of shadowing or sunshine is primarily carried out by means of the German standard DIN 5034-1 which recommends for housings a minimum sunlight duration on 17th of January of one hour and on 21th of March of 4 hours. But also the percentage of decrease of existing sunlight duration by a building project is consulted as a criterion for the assessment of the legitimacy of the planning.
In this paper the principles of forecast of shadowing duration in urban regions are outlined. In particular the self-shadowing of buildings as well as the influence of the horizon constriction on the calculation results are explained. Furthermore the connectivity of the building dimensions with the algorithms of the calculation model is outlined. Here shades are exclusively understood as differences in brightness of directed sunlight created by buildings; that means, effects by diffuse skylight, artificial lighting, reflections etc. causing shade phenomena remain disregarded.