Unfortunately, I need to watch my budget carefully and build as cheaply as possible. I have now received a quote from a roofer for roof insulation. He suggested installing 12 cm (5 inches) of mineral wool between the rafters and adding 6 cm (2.5 inches) of wood fiber insulation on top of the roof. He believes a vapor barrier is unnecessary because the attic is already fully finished, and the layers of drywall, cement board, and wood-cement panels already act like a vapor retarder. If moisture should condense on the insulation, it would dry out quickly.
Is this correct? Can I really skip a vapor retarder?
Is this correct? Can I really skip a vapor retarder?
5 answers and 5 different opinions. Unfortunately, this is exactly the same among roofing companies. But I do not skip installing a roof membrane. In our old building, I also installed the roof membrane as a foil. There is simply no gap between the boards, so moisture cannot escape. Therefore, a roof membrane is necessary for me.