The invention relates to a window mounting system comprising: a building facade having an interior face and an exterior face and comprising a window opening; and a window mounting collar formed from rigid thermal insulating material, the mounting collar having at least one inside face, at least one outside face, a first open end and a second open end; wherein the window mounting collar is affixed to the exterior face of the building facade so as to surround the window opening and extend outwards from the exterior face of the facade, such that the first end of the mounting collar is proximal to the building facade and the second end of the mounting collar is distal from the building facade; wherein the system further comprises a window frame arranged in the mounting collar such that the window frame is separated from the plane of the exterior face of the building facade by at least 10 mm.