We have an addition to the house that needs to be converted into a living space (kitchen). So far, the roof has been built with a simple boardwalk structure and roofing felt (double layer). Now we have installed exterior insulation on the roof, including everything that goes with it (photo 1).
Now we're wondering how we should/could seal everything from the inside so that we don't have a mold problem. Up until now, this has been an unheated room, and the roof itself has been well ventilated – the unplastered part + the wood (see photo 1) was only covered with wood boards on the outside. We would like to hang the ceiling inside again on the surrounding bottom beam (green) (picture 2). But now we still need to ensure that the roof structure is airtight. Currently, between the roof beams at the front we can still see the exit to the outside (picture 3).
Does anyone have any advice on the best way to build the ceiling from the inside, including sealing (key word: vapor barrier)?