Originally Posted by charlie1025
Question: if so, what are the possibilities of finding a 'finished' (like wallpaper) surface facing the living space? Question: is it necessary to apply a skim plaster coat or retardant paint over the product?
To my knowledge, no such product exists, at least from a commercially reputable supplier. I am not a code expert, but I believe most areas require the insulation be mounted behind a thermal or ignition barrier such as plaster or drywall if the space below is occupied. If you want to insulate to solve your problem, you should prepare yourself that this will be a fairly expensive retrofit. That cavity is going to have to be opened from one side or the other to get a suitable amount of insulation into that roof.