Removing tub to install walk in shower

[Maveric169]

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.

 

[TomFOhio]

Can you build a false ceiling a few inches to get your pipe in it?

 

[Maveric169]

Can you build a false ceiling a few inches to get your pipe in it?

That was what I was thinking of doing, as it would keep the pipes on the warm side and reduce the risk of freezing.

Like I mentioned it is always hard to determine if I need to do the extra work of building out the ceiling an inch or not as there is so much conflicting information out there. Some say just run it directly along the ceiling, under the blown insulation, and insulate the pipe and I am good, others say no anything run in an attic space will freeze.

 

[Diehard]

The way I see it is, if you were getting condensation on bathroom ceiling on the coldest days, there's a chance it could freeze being on the other side of the ceiling. Then there's the thought that a false ceiling approach only puts the pipe one ceiling thickness away from being located under the insulation.

But if you have anywhere near the insulation you should have up there, I highly doubt it would freeze.

Then there's the chance, depending on exactly what is proposed, there would never be standing water in that line anyway.