Have this damp sport just above the airvent and next to the boiler cabinet in my spare room. This happens to be the warmest room of the house, and we often hang our washing in here, tho I remember seeing this spot even before we moved in, so don't think that makes much difference! Could this simply be as wet air is being attracted to the that particular cold spot? Ive put my hand in front of the air vent and you can feel cold air come through! TIA for any help!
