Goedjn wrote:


Tempering valves only add enough hot water to get
somewhere near room temperature. Nobody's suggesting
replacing the cold-water supply with pure hot water.

I'm glad that's being clarified, but I'd still be more confortable with
something lower-tech with no possibility of malfunction and the ensuing
rotting floor.

Insulation is good, and the best solution is dealing with the excess
humidity that will likely cause other headaches (i.e. mold). Even
putting a longer run of copper pipe outside the humid bathroom would
allow the extra cold water to get closer to room temperature before
entering the bathroom area, but that wouldn't be my first choice.