Abstract: The invention relates to a window having a channel between its glasses, through which channel circulation and/or fresh air is brought into a room. The object is to provide a new window which can function as the only heating element of the room. This object is achieved by providing the glass facing the room with an electrically conductive layer, whereby the said glass functions as an electric heating element, and by providing the inwards facing surface of the outer glass with a coating reflecting the heat radiating outwards from the heating element almost entirely back into the room. To make the recovery of heat more effective, a fan with actuating and regulating devices is preferably arranged in the window structure.