You're getting brave even thinking of putting a hole in the building - roof or wall. Now the garden is big enough to get a ground source heat pump in ........... afterall you've got plenty of time to dig the garden up and lay the pipes now you're a man of leisure I think you're gonna have to fit some form of heating for Lis, after all the sound of chattering teeth can be awfy distracting, especially when there yours as youve been swapped ends for the winter Paul