I have two large patio door/window ombos in my nice modern spacious ‘executive’ detached family home. I’m not at all sure why the developers feel that 2 such doorways were essential to make comfortable living. All around the house I have very good and presumably effective double glazed window units. I’ve never had reason to query these installations until the other year when one of the bedroom windows started showing signs of internal condensation gradually the window became completely fogged up. Eventually I looked up suppliers of windows and double glaing units and rang them for advice. Needless to say I’d been anxious about nothing – they were able to come out, check the situation and quoted me for a replacement double glazed unit. The price wasn’t too bad, all things considered. The had to remove the entire opening window, remove the double glazed element, swap double glazxed panes ad completely resdeal it all before hanging the window back into the frame