[nanomonkey]

I think you could get away with two insulated reservoirs (frozen and hot water) and then use something like glycol, alcohol or water to shuttle hot and cold to your shower, under floor heating/cooling. Frozen water can be mechanically stirred (like a slushy machine) to keep it from freezing solid, allowing you to pump it through pipes. Water can also be mixed with salts or alcohol to alter it's freezing temperatures, with allow you to move cold from your freezer to the refrigerated areas (fridge, computers or living spaces). You can also use air as a working fluid. Any excess can be dumped to the outside environment with a radiator as a last resort.

Modern cars are already doing this with heat pumps to manage batteries and the cabin temperatures.

It's pretty easy to see where building technologies will go by looking at car technologies...