I have excessive condensation on my bedroom windows on cold frosty mornings. This is causing mould on my blinds and curtains and also the bedroom wall. I have wallpaper on one Wall (Over the bed) the corner wall has black mould forming and also around the skirting. I have the heat on in the evening and it goes off while we are in bed and comes on again in the morning. My windows are double glazed and its a bay window with a lead cover on top where the windows sits out from the tiled roof. The house is 10 years old, there is a vent in the room but i close this as its over my head. What would be causing this and how can i prevent it?