We have a terraced house in London, kitchen at the rear with 10 year old wooden Double glazed french doors with double glazed window each side ( these we rarely open) we have another single side door (Half double glazed). The kitchen is cold in winter and we are looking to up grade the doors/windows.
My query is ; What if rather than replacing the doors / windows could another (2nd) double glazed window be attached to each the outside of the doors/windows as a "Secondary glazing option ?