Hi, I have got a problem with black mould on the ceiling in our smallest bedroom. It appears along the edge of ceiling where it meets with the top of the outside facing wall. I would like to know how to deal with it and what to use and also would like to know what the most likeliest cause is, i.e. could it be from poor circulation/ventilation in the room or could it be from the loft area above, perhaps from loft insulation? Any advise would be much appreciated.