In this paper external fixed shading device geometry is optimized in order to reduce the overall energy consumption in an office room provided with an extensive glazing and moveable Venetian blinds. The fixed shading device is a flat panel positioned parallel to the window and inclined by its horizontal axis. The energy consumption takes into account the energy required for maintaining internal conditions considering heating, cooling and electricity absorbed for artificial lighting. A multiphysic approach applying different simulation codes has been implemented along with RSM and genetic optimization algorithms.