out side wall shower plumbing?

I have to set a shower control on an outside wall (East side of house in the Seattle, Washington area. it is a 2X4 wall temp get to mid 20"s a few day a year. What is my best course of action. I have no other wall to place control..Heeeelp.

Insulate the wall and pipes.

In Seattle, keep the insulation on the far side near the outside wall.

Don't let insulation get between the warm side of the wall and the pipe.
The pipes need access to the warmth of the home.