Light environment in Japanese office buildings after 3.11 earthquake

The purpose of this study is to reconsider the optimal lighting conditions in office buildings with respects to the occupants' visual comfort and reduced energy use. This paper reports on how the lighting in office buildings in Japan has changed after the events of March 2011, the Great East Japan Earthquake. As the first step, nationwide questionnaire survey of the measures for saving electricity was conducted on the facility managers in office buildings. Secondly, field measurements to identify the actual lighting conditions in 13 office buildings were conducted, as well as evaluations of the lighting conditions by the occupants. The results showed that for about half or more buildings saving measures for lighting and for air-conditioning in summer season were taken. Especially for lighting, about half of the ceiling luminaires were turned off and the desktop illuminance was reduced by half compared with that before the earthquake. The occupants in the measured office space were still satisfied and evaluated their task area as rather bright.