Energy-saving reconstruction structure for external facade of old building

The utility model relates to the technical field of old building reconstruction, in particular to an old building facade energy-saving reconstruction structure which comprises a wall body, a window is formed in the wall body, and a reconstruction mechanism is installed on the wall body. The transformation mechanism comprises a back plate, a bottom plate is fixedly arranged at the bottom end of the back plate, a top plate is fixedly arranged at the top end of the back plate, and limiting side plates are integrally and fixedly installed on the two side walls of the back plate. When the light sensor detects that the sun disappears or extreme weather such as night, rain and snow, the motor is started to drive the screw rod to rotate, the screw rod is meshed with the moving rod, the moving rod moves along the limiting groove through the sliding block, the moving rod drives the solar panel, the solar panel moves along the guide groove through the rail wheel, and the solar panel is in a vertical state when descendin