The window is a structural element of residential buildings, thanks to which we can ventilate rooms, as well as provide some daylight. Rows of identical windows are characteristic especially for multi-storey tower blocks and blocks of flats. Despite the fact that dimensions of a window, as well as the type of frames and sashes are unified, residents often try to decorate glass panels so that they stand out from the monotony of "squares" of the front wall of the block. However, decorative curtains, cafe-style curtains or pots of flowers are not always visible from the outside. This phenomenon can be explained by physicists. The windows set in the background of the sunny side of the building may appear black even during the day as the light coming into the room through the glass is almost completely absorbed.
