I have all vaulted ceilings on my first floor, no attic. The current insulation is faced rock wool bats which have settled over the years, (home built 1960). I plan on opening up and removing the ceiling dry wall to do some remodeling and re-wiring. I also plan or replacing the insulation. Should I also install a radiant barrier to the underside of the roof decking before installing the new insulation and dry wall? I'm in Memphis and yes the ceiling gets very warm to the touch.