Abstract: The present invention refers to a heating and air-conditioning system for one or multi-storied buildings with multi-glazed windows contained in the facade of the building. A fresh air entrance arrangement is disposed below at least one of these windows on the outside of the facade of the building. A fresh air processing device is connected to the fresh air entrance arrangement with means to filter, heat or cool and humidify the fresh air and to expel the same over a distributing cavity arranged beneath the window. The distributing cavity is connected to a window cavity between the panes of the multi-glazed windows. An entrance opening arranged at the top end of the window, connected to the window cavity, extends over a good part of the width of the window and opens out toward the room to be air conditioned. A stale air flow out arrangement controlled by valves directs stale air out of the room.