Heloo , I’ve just bought a long wheel base Citroen relay , taken all ply out as it was a work van before, My plan is to run 25mm batterns along and glue them down and use leftover rock wool scraps to insulate in between. then wondering about a breather membrane on top of that breathing inward so that the insulation/batterns have some airflow, or would it be worth using shiny foil barrier so it can’t breath but reflects more heat? does it even need that? Then something free/cheap to finish maybe just clad/ply.
Any thoughts / recommendations?