Hi, in winter there are water droplets forming in the roof void's ceiling osb board. These drip causing mould patches on the flat ceiling. Is the solution (1) add more insulation rolls/boards/foam in the roof void, or (2) add vent to the flat's ceiling (3) add mushroom vent onto the top of the roof? or a combination? I don't want to make the matter worse as in some instances adding more insulation does. I also don't want to rip off the the whole ceiling and add insulated vapour plasterboard. I know it's something to do with it being 20 degrees in the room and zero degrees on the roof. Many thanks in advance