I am going to be renovating my master bathroom in a few months but have gotten some conflicting information so I need help. I am removing the current tub/shower combo and going to be installing a walk in shower. My wife would like to have a 2 rain head shower heads from the ceiling or one on each side of the shower. The problem is that the opposite wall from the current shower head is an exterior wall (#1 in the image), and above the ceiling (#2)is the attic with blown insulation. I have read that I both can and cannot run the plumbing in those 2 spaces. I live in northern Indiana, so our winters do get quite cold. When I do the remodel I was planning on using pex, but I can sweat copper if it matters. So my question is, can I run the plumbing in the attic space and/or into the exterior wall, or would it be better to build a 1" bulkhead and just run the plumbing in there instead? Additionally, because of the scope of the work I will need to get a homeowner permit, so I need to be careful about what is allowed by code.