In the building of 'Hokkaido northern regional building research institute', daylight is used for indoor lighting positively. In the winter, so much daylight reflected on snow come into the room. The rolling screens are closed in the case of the vertical illuminance out of window is over 100001x, and the artificial lights are switched on in the case of it is under 200001x, gradually by human. More than half of daytime, illuminance on main desks is over 10001x. Electric power consumption for lighting is very small in this building.
