We have a basement flat and we suspect that the bathroom exhaust fans do not go anywhere, which causes a fair bit of damp in the flat which manifests itself as condensation on the windows in the winter.
I'd like to fit an extractor fan, or at least some sort of vent to allow the air to circulate (this should help with the condensation shouldn't it?), but don't want to drill through the wall as there is a damp proof membrane in there. Can I fit something into the window, and how do I go about cutting a hole in the glass to accommodate it? I've seen those cat-flaps that are in the windows so I assume it must be able to be done...