Your new windows can only prove their benefits in terms of functionality, aesthetics, reduced energy consumption and optimum acoustic protection if they are fitted correctly.

Unfortunately, it often happens that many installers replace the window, leaving the old frame , it is a bad habit, very common only in Italy.

Instead of removing the frame of the old window , it is covered by hiding it .As if to say: instead of cleaning the room, you sweep the dirt under the carpet. Removing the frames requires time, effort, skill and caution to avoid damage.

It costs more and is more difficult.

Those who work by piece prefer not to do it: but the final work suffers, in terms of brightness (the glazed surface is reduced ) and thermal and acoustic insulation (the insulation is less effective), even if at first glance it is difficult to notice.

The manufacturers of PVC windows and doors have adapted by creating windows with a so-called Zeta profile or restructuring , suitable for masking the old frames, especially for the Italian market.

Generally there are 2 different installation techniques to replace a window 

Laying in “overlap” : the new window is laid over the frame of the old window which is not removed.

It is the simplest way, it takes less time and effort, it is the method adopted by the vast majority of installers: in a few minutes only the sashes of the old windows are removed and the frame is left anchored to the wall, so the frame of the new window will simply be screwed to the old frame: 2 frames !! old and new, and since the window opening is always the same it is clear that the sashes (including the glass surface) of the new window will be smaller !!!


  • It’s much simpler, it takes less time and effort.
  • The installation, for you customer, costs less (should?), Certainly costs less for installers.
  • Even the new window costs you less (should it?), Being smaller than the existing one.


  • The new window is about 8 cm narrower and about 4 cm lower, light is lost from the window, both when it is open and when it is closed: the glass surface will be reduced and a lot, especially for those narrow and high windows .
  • Poor optimization of thermal and acoustic insulation: the separation surface between the old and the new frame, along the entire perimeter of the window, cannot be properly sealed, because when installing the new Zeta frame or renovation frame it is not possible foaming between the old and the new frame. The result is that despite having purchased a window with very high thermal and acoustic performance, the actual advantages are only very limited: noise, drafts, heat, cold pass, they are not kept out of the house.
  • The old frame, with previously mentioned, is hidden with special profiles (Zeta, renovation) or with rather thick architraves: to the detriment of the aesthetic result which is not very pleasant.