I am getting ready to remodel a bathroom. One of the walls of the bathroom is an exterior wall with Kraft faced insulation, should I remove the current insulation and replace it with non-face insulation and poly vapor barrier? The insulation or studs shows no signs of moisture or being dirty from air movement. Also the interior walls had no insulation, I was thinking of insulating them, for no other reason than sound, on these interior walls be are going to be tiling 42" up the wall. I know I need to use a water proof membrane in the shower area, but should I also put a membrane of the walls outside the shower/tube area?