The purpose of this research is to study the types of fenestration for daylighting utilization in office buildings on the north and south direction. The study emphasizes on an application in sky condition and climate in Bangkok. Data namely sky luminance, radiation are collected for one year record, 1999. Then all data will be grouped into three conditions by sky ratio. Those are clear sky, partly cloudy sky and cloudy sky in order to simulate the side lighting in difference sky condition with computer program, Lightscape 3.2. The validation of computer program is audited by comparing between the estimate result of illuminance and measurement by light meter with in building. A standard room was set as a case study. The standard room was 9*9 square meters with one side of fenestration, single 6 mm. glass. The fenestration was divided into 2 types those are strip window and punch window with window wall area ratio 70%, 60%, 50% and 40%. The result of illuminance on work plane was evaluated daylight in buildings from north and south direction. The evaluate of annual electrical energy consumption on types of fenestration in this research is to compare with the reduction of energy for illumination from artificial lighting and the increasing of energy for cooling load by heat gain through window, heat gain from artificial lighting. This research shows that strip window efficiency when the window wall area has ratio at 40% to 50%. If the window wall area ratio increase 10%, the cooling load will increase about 16%-25% in the north direction and the south direction. The results of illuminance by computer calculation are conclusion that strip window gives quantity of daylight on work plane at 4.7 m. maximum with ratio daylight area of standard room area should higher punch window. If the higher part of window above work plane equally 1.95 m., the lower part of window will be increasing to 0.15, 0.45 and 0.75 m. This has an impact on the total level of window and distance of shading device are increase. This also has an impact on the reduction of interior illuminance on work plane. The increasing of opaque distance between glass of window results in the reduction of interior illuminance on work plane in north direction more than in the south direction. The conclusion of this research is that the strip window which have the higher part of window above work plane in the north direction will have higher efficiency than others. This research will work as a primary data for architects to consider the design types of fenestration in office building in Bangkok for daylighting utilization which high efficiency for energy conservation.
