I moved into an 1850's house. In the report it highlighted the roof lining was a non breathable plastic sheeting (probably fitted in about 1986) and as such is contributing to high moisture levels in the loft. Well, that and a uncovered water tank (now done).
The report suggests adding additional tile vents. However, I would ideally like to replace the roof felt with a breathable type. The current one is fitted between the roof timbers and the tiles. Is this a difficult/costly exercise? Or in theory can this all be done from within the loft, without need for access from outside?