Storm damage repair–shower wall issue (vapor barrier?) – GreenBuildingAdvisor

I am in zone 2.  I am working on repairing a storm-damaged house that was built in about 1914 and is not air sealed. It was added onto in 2000 and no sheathing was used by the person that built the addition.  We have been adding plywood sheathing plus new insulation, siding and drain wrap (and replacing any damaged dry wall) to the walls that don’t have any exterior sheathing.  We got to a wall section with a shower on the inside and discovered mold visible from the outside on the shower substrate (some sort of tile backer board or just plain drywall).  We now need to redo the shower.

I read the following thread: https://www.greenbuildingadvisor.com/question/is-the-shower-wall-a-vapor-barrier . The responders say that the shower surround is a vapor barrier and mention being meticulous with air sealing.  We have been doing our best to seal the exterior plywood we have added to the 2000 addition, but the top of the bathroom wall appears to open into the soffit and the floor (the shower is on the 2nd floor) opens to other areas of the house that aren’t air sealed at all. We will do our best to seal the bathroom wall from the soffit on the inside.  I can’t redo everything though nor do I have access to redo everything.  The shower has 2 walls that are located on exterior walls of the house.  It also goes all the way to the ceiling and the ceiling has tile.  From reading the thread, it sounds like it will be a vapor barrier once installed correctly which we aren’t supposed to have in our zone.

It sounds like my best bet might be to air seal the area where the shower is now and not go all the way up to the ceiling with the new shower so that it isn’t a complete vapor barrier on the section of wall that makes up the shower.  My husband would prefer that the shower go all up the way up to the ceiling.

Questions:

1. Should I limit the height of the shower to keep from having a complete vapor barrier on those sections or is there a way to have it go up to the ceiling that won’t cause issues?

2. I’m open to using any materials needed to air seal the walls of the shower.  Do you have any recommendations?

3. My husband likes the Schluter Sealed System, if you have experience with it or other systems you like that you think a layperson can handle, it would be great to hear about your experience. I’ve been looking for a contractor and most have a minimum they want you to spend-this is a very small shower.

Thanks for any assistance you can provide