I'm remodeling a bathroom and planning to use tIle over hardibacker around the tub/shower. From other posts I know I need to use a 6mil vapor barrier behind the hardibacker. However, the house Is a duplex and one wall is shared with the other unit. I'd like to insulate between them to cut down on the noise transfer, so should I use unfaced insulation here, rather than have two vapor barriers?
Also, I wanted to tile up the wall about 3-4ft in areas outside the shower like behind the toilet and vanity. So would I use the same poly vapor barrier behind the hardibacker here and then faced insulation behind the greenboard above it?
There were major moisture problems before so I'm just trying to avoid repeating the situation. Thanks for your help.