I've installed a rough-in valve on an outside wall that has brick on the exterior, R-13 insullation between the valve and the exterior, and drywall in front of the valve. My problem is that the valve will go through the mirror which has cut-outs for the stems/spout. I was planning on leaving a drywall cut-out around the valve, behind the mirror, for future work (if necessary), but I am concerned about condensation ruining the mirror.
Any suggestions? I was told to line the valve with visqueen (?) or an old shower curtain. But shower curtains mildew. Does visqueen? I am open to any and all help. Thanks....