Abstract: Due to increasing awareness of the importance of energy efficiency, daylighting features such as light shelves are becoming more and more popular. A light shelf is a horizontal or inclined projection with a high reflectivity meant to increase the depth of daylight penetration into a room. Currently, a light shelf is treated as a passive design element. It is designed to maximize the average distribution of daylight during the operating hours of a building and its geometry is not adapted to the changing conditions during the day. This article discusses a methodology for the active control of light shelves. A light shelf system whose geometry can be adapted is presented. The control of this system is treated as a global optimization problem. Geometrical parameters of light shelves are computed in real time to minimize the energy required for artificial lighting. An example of an office building is taken to illustrate the hourly energy savings possible through active control. It is demonstrated that building automation and control have considerable potential for energy savings. No claim to original US government works. © 2010 Computer-Aided Civil and Infrastructure Engineering.