ok so I accepted a cold call invitiation as the first ploy of the energy saving call was externally beaded windows and security, then special thermal coating for walls, but then I have a wide bedroom window on which condensation forms at times on the room side of the glass.
The 'surveyor' came with a meter that either showed Red or Green. A window unit I know that had been recently replaced new glass showed, as it should, Green as did the very large lounge window.
The bedroom window showed Red. I joked about "Press once for Green, press two for Red" but the meter seemed genuine. So what is it and are they any use?
And any clues on the condensation on the inside (not between) the old wide window? It is on a North side wall which never gets any sun.