The outer side of the shutter or awning has a reflective surface (1). The pivotal range of the shutter or awning w.r.t. the facade (7) is greater the 70 deg. A facade solar cell module (4) or collector is installed above the window (3). The shutter or awning can extend sideways over the module or collector. The supports (5) are pref. telescopic and operated by a compressed medium. The effectiveness of the latter can be according to a programmed control. The latter can be made dependent on the weather, a weather sensor being duly provided.
