The window frame in the wall forms a niche between the ribs to which the outside wall is connected. This niche invites to make a neat frame around it and therefore making an extra wall. Although extra work, it gives the opportunity for other facilities which are illustrated below.
12 mm birch plywood is connected with rivet nuts to the wall and glued to a vertical profile in the niche of the window to make the window frame
4 plywood plates are connected with dowels and Kreg-connections to the floor forming the niche of the window.
Horizontal and vertical profiles are glued to the plywood plates and make the window frame. The parts touching the window are provided with rubber U-profiles to protect the window.