North-South vs East-West: The Impact of Orientation in Daylighting Design for Educational Buildings in Bangladesh

摘要

Day lighting is one of the important environmental factors that affect the health, emotions and academic performance of the students as well as the energy consumption of the educational buildings. These days it is obvious that designer must consider both the quantity and quality of the day lighting system of the building. In educational building windows are considered as the main fenestrations to provide proper daylight and natural ventilation. Daylight coming through the window depends on some internal variables (fenestration’s size, shape, position on the wall, materials, colours, reflectance, transparency and space geometry). Besides these internal variables designer should consider some external environmental variables climate, sky condition, orientation of the building and orientation of window wall. In efficient daylight design these internal variables varies according to the external variables especially according to the orientation of the fenestration or window wall. During clear and partly cloudy conditions, each of the four cardinal orientations offers a light source that contrasts in both character and illuminance levels. But unfortunately daylighting haven’t been designed well at most of the educational buildings in our country. Some prototype window having same size, shape, materials, shedding and control are used in same position in walls at any orientation. So, either glare or duskiness phenomenon is often happens in classrooms and dependency on artificial lighting is increased. This study examines the impact of lighting distribution of the same prototype windows in different wall orientation. This study also shows how different window’s shapes, sizes, geometries and positions in different orientation respond to lighting distribution. This paper deals with light coming into the rooms through the window, where window is considered the only system to provide, control, and distribute light flux. ECOTECT and Radiance software are used to simulate the proposed window conditions. This study explores a new daylighting design method and process for educational building. This study can be used to build sustainable education buildings that are highly efficient with low running cost.