I recently moved into a 10 year old house. The master bathroom shower is tile. Some of the grout was breaking down. As I was cleaning out the joints for regrouting, I discovered the drywall behind the tile was wet. There was no vapor barrier between the drywall and the insulation. The shower is on an outside wall. Long story short I have removed the drywall and the insulation. Do I need a vapor barrier between the Hardibacker and the insulation?