i have tried everything to stop this mold, it is on the upstairs bedroom walls only in certain places, in the corner of my daughters room and my sons room, there is a rad in each room and the rooms are well vented, there is nothing in front of the offending walls, i have had the cavity wall checked and that is fine i have put polystyrine lining paper on the wall to warm the wall up but that did not work, it is not all over the walls just in some places, can anyone help.