In an urban site, daylight strategies increasingly depend on the availability of natural light, which is influencedudlargely by the immediate surroundings of the building, particularly the presence of natural andudmanmade obstructions. Under such conditions the latitude of the site and its regional climatic conditions,udsuch as ambient outdoor daylight levels and sunshine probability are found to have diminished direct impactsudon the interior daylight potential. In these highly specific urban environments created by built-upudsurroundings, no generalised way exists to describe or predict the luminous microclimate. However, simulationudcan be used as a design tool for sustainable daylight design. Using simulation programs, this paperudexamines the significant impact of surroundings on daylight probability on urban buildings. Daylight simulationudwas performed in this study by creating the virtual urban environment based on the informationudof a true site urban office building in Dhaka, Bangladesh, a tropical location, with predominantly overcastudskies. The 3D models were first generated for computer simulation in the Ecotect program to calculateudthe amount of daylight incident on a generated grid point on the work-plane. These models were then exportedudto Radiance Synthetic Imaging software to generate realistic lighting levels and finally verified withudDAYSIM simulation program for annual performance evaluation. The results show that daylight enteringudfrom different sides of the building is affected vastly by surroundings and this influences the indoor illuminanceudand luminance distribution. This paper also demonstrates a case of decision-making between twoudmost popular configurations (vertical and horizontal) of internal blinds used in urban offices of Dhaka. Theudfocus of the paper is to highlight the importance of daylight simulation in sustainable urban office buildinguddesign, while at the same time gives a general methodology for decision-making regarding daylight designudelements.
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