heating for bathtub bottom surface?

As winter approaches, I'm reminded of how I hate to step into the bathtub in the morning to shower. Until the hot water warms it up, the bathtub "floor" is very cold. My bathtub is over an unheated basement, currently with no insulation, and even if it was insulated I'm not sure it would be much better. We let the house get pretty cool at night. I'm in Atlanta, so most of the year everything's nice and warm ...
I'm about to gut that bathroom, including the floor structure, and completely rebuild it. It occured to me one recent cold morning that while I'm replacing the bathtub, I could get some sort of heating pad or coil affixed to the bottom surface, and rig that to a switch or a timer or something.
I've looked on the net and I can find no such product. All I'm finding is A) jacuzzi tub water heaters and B) radiant floor heating systems. I don't want to make a science project out of this and rig up something myself, because, among other reasons, I bet there's some code issues to worry about with putting an electrical heater directly below a bathub.
Has anyone seen some kind of product that heats the bathtub bottom from below?
- Chris
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snipped-for-privacy@pobox.com (Chris Campbell) wrote:

you could wear some neoprene scuba booties to keep your feetsies warm for that 60 seconds it takes for the tub to get warm.
you think you've heard it all...
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(Chris Campbell) wrote:

That or move the tub indoors for the winter.
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Chris Campbell wrote:

Well, you can have a heater on a timer (safest would be an oil-filled electric radiator-type heater), so the bathroom is warmed up in advance. Or you could insulate. or you could put in warmer floor materials.
So the house is on a timed thermostat? Why can't you start the morning warm cycle earlier?

OK, what about (B) didn't appeal to you? It looks like exactly what you're talking about here.
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Either that, or flip it upside down. Run the heater from say, 8PM to 8AM. It shouldn't cool down as much during the day. No more cold tub. -Dave
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I live in Hawaii so cold bathroom fixtures are not an issue... but, on a winter trip to Japan I experienced a heated toilet seat. True luxury after a few earlier chilly encounters. [The Japanese generally use furos - not showers - so not likely to have a solution for the cold feet.]
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The easy way out is to turn the shower on first and let the hot water do the warming.
If you have hot water heat, a loop under the tub should help.
When I redo my shower, I intend to try and figure out how to warm the outside wall a bit. I am now thinking of tiling the floor, running heat under the floor and feeding off that system under the shower and up the outside wall.
I would be hesitant to use anything electrical to heat the tub.
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Better, IMO, to do what I did. I used Styrofoam panels to exactly come out to the edge of the studs. No heat lost, no colder walls serving as a condensate site for shower water in the winter. No mold accumulation, at all, in the bathroom since the renovation. And whatever the inside house temperature is running, that's going to be what that outside wall is going to be. Sure is a big difference from before, when you could watch the wall 'sweating' moisture on it from the chill on the outside.

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You can install hot water radiant loops under the tub (and the floor of the bathroom for that matter). If the basement is not sheetrocked, it can be done fairly easily and use your domestic water heater as the heat source (through a heat exchanger).
I'm in the Atlanta area and have done these before.

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On 25 Oct 2003 17:34:24 -0700, someone wrote:

Insulated between the joists under the tub and it will be MUCH better.
What you are saying is like saying "my walls are not insulated at all and my house is cold, but I'm not going to insulate because it might not be much better."
Insulate now.
When you rebuild, raise the floor under the tub a few inches and sandwich some solid foam in there between the existing subfloor and the new layer.
Or run radiant, but that is a whole 'nother system if you are not already circulating heating fluid. Many people like radiant for the whole bathroom because they find their tile floor cold, you would just be running it under the tub also.
-v.
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At another house, I put styrofoam 'popcorn' into the access under the tub, blew it around to settle under the tub. Then kept adding more.

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snipped-for-privacy@pobox.com (Chris Campbell) wrote in

Tuck (not pack) fiberglass insulation around the uderside of the tub. Use an acrylic tub rather than cast iron, as they warm up much faster.
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I have just seen a Home Depot ad that had a floor heater (called Warm Tiles) advertised that fits under tile. It's an electrical cable type heater. For a 20 sq ft floor, it costs $80
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