Here's the concept: For the hot water usage in a bathroom, does it make more sense to put heat into the shower water, or to heat the shower stall?

So with all this talk about drainwater heat recovery, it got me thinking. If you had all the walls and floor of a shower stall with radiant heating, could you create a more comfortable experiance with lower shower water temps? Is it more efficient to heat the room and bodies within it than the water that will be going down the drain?


Thoughts?

I can't say the idea is mine, but at a hotel we stayed at had a large walk in shower with a swing door. The unit had a steam option and if you turned it on 5 minutes before the show it was nice and toasty warm when you stepped in. So when we built we basically enclosed the shower and it takes very little time for the whole shower to become comfortably warm and if my wife takes a shower first it is really nice and warm when I get in. I do leave the door open once were done taking showers to dry it all out. The other HUGE advantage is I can shave while my wife is in the shower since the mirror doesn't fog up.

So it's not exactly what you’re talking about, but having a closed space is great.

I have heat lamps in the shower. I think it heats more evenly and allows slightly cooler water. Heating air or surfaces is far less expensive than heating water. Warm walls also makes sense, at least in the winter.

Would enough radiant heaters + reflective surfaces allow comfortable showers without heating the water? Maybe.

How hot do you think the surfaces of a three sided tile shower would be comfortable?

I like the idea of closing in the glass door panels to create a mock steam room, would eliminate any drafts.

Ahhhhhh, the most comfortable, I think, is to have heated walls and floor and the same, or very slightly cooler, water temp!!! That's the way my shower is.

I have a totally enclosed tiled shower with a built-in bench and a custom sized bifold glass door. I used Warmfloor brand low voltage heat mats in the walls, the floor, and the bench. The shower is 5' x 5'-6" and the heat mat load is 500 watts. The heat turns on about 2 hours before shower time and I can feel the warmth radiating from the walls when I step in there. The walls are not so much warm as they are not cold. The mats are self regulating and won't go over about 85°F.

The cost of installing and operating (~$0.07/hr) the heat mats is the price I pay for hedonistic comfort. Energy efficiency wasn't part of the equation, as it was in all the rest of the house design! I did have the insulating contractor spray foam all the shower walls and bench from the backside so they are well insulated. I plan to put rigid foam under the shower floor. I am trying to figure out how to do drain water heat recovery in the presence of a crawl space only. I do believe though, the heat mats cost less than the hot water that otherwise would be used to heat the shower walls and floor.

P.S. I also have stereo speakers in the shower so I can listen to news while showering! I figured if I'm going to spend over $300k to build a house I can do at least this much for pure self enjoyment!

From a practical view,
Perhaps you should heat the floor so when you use the bathroom the room will be warm, wether or not you are in the shower. Your heated floor will not affect the delivered water temp spraying on your head.
If you do not have pipe in the floor the floor will quickly warm as the water hits it.
Will you save on more water down the drain thru your copper pipe heat recovery gizmo,? I suppose so, maybe, maybe not.
But if the shower pan is warm, hit with pipe when you do the infloor heating it will aid in heating the room when the shower is not running, and your naked toes will not get cold.
Good luck,
Dan