I have a classic 1930's semi, and I think I have a condensation problem in my loft. The rafters have mold on them and occasionally feel damp to the touch. The damp appears to be be seeping down from the roof side of the rafters. I am thinking about fitting LapVents but I wanted to ask about moss etc. The tiles appear to have a fair bit of moss etc on them, which occasionally comes off and falls to the ground. Could this be blocking air flow between the tiles?