black mould is caused by thermal bridging , the warm moist air cant escape and reaches the cold outer panels, don't know much about c,vans but guess they are cold outers with little air circulation, i get this all the time with on-suites that are not vented outside, try insulation on the outer panels or just a 12v fan to take the moisture out remember mould spoures only stick and turn black when there is no air flow hope this helps or you can call me on 07711304567 for free advice john
clarkeinteriors, July 2010
