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The purpose of this study is to reduce discomfort caused by the change in the brightness of windows by changing the speed of the slat rotation. In order to identify the degree and the frequency of the change in luminance of the windows with blind controls, a numerical simulation was carried out by using weather data. An experiment was carried out in a test chamber to identify the effect of the change in the window brightness on the subjective response. The results of the experiment showed the effect of slat-rotation speed and the change in window luminance on "Discomfort caused by the change in the window brightness" rated by the subjects. In this study, the method for determining slat-rotation speed of blinds was proposed based on "Discomfort caused by the change in the window brightness" obtained from the subjective experiment.

In order to utilize the gradation blind more effectively, three algorithms have been added to the original control algorithm. The first algorithm calculates the area of the shadow of surrounding buildings and exterior solar shading. It can reduce lighting energy use and obtain a clearer outside view. The second algorithm determines the target slat and its optimal angle. The third algorithm minimizes the sum of the lighting energy and the air-conditioning energy. A survey was carried out in a building using the gradation blind with the new control system. The results show that the new control system can achieve better human comfort and energy saving.

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This study explores the transition of illuminance of Japanese office environment as well as subjective evaluation toward brightness by reviewing existing scientific literatures of over half century. In total 484 data of illuminance of actual office and 28 literatures which studied the relation of lighting environment and subjective evaluation were extracted. In the last over half century, the illuminance of office environment have been increasing along with the recommended level of illuminance of JIS. Before 1980s, the actual illuminance level of Japanese office was higher than the recommended level of JIS, and then it became to be settled on or less than the recommended level of JIS standard. The subjective evaluation of illuminance also have been changing since 1950s. Before 1970s, people satisfied lighting environment less than 300 lx, and people became to be unsatisfied of 300 lx after 1980s. On the other hand, illuminance level of 750 lx has been evaluated positive consistently since 1970s.