Window including a rectangular frame, which supports and encloses at least two panes separated at a certain distance, a slab being placed between said two panes, said slab having a width corresponding to the width of the panes but having a height which is smaller than the height of the panes, said slab being displaceable up and down by a current of air which is introduced in the frame under the slab and is let out above the slab or vice versa.
