Thanks for all the input; it's been really helpful. Shanghaimom, I did a 'step test' with a 12x12 marble sample I had on hand, and you're right; it is so much colder than the tile. That has convinced me to install floor heat, even if it's only a secondary source. I had no idea that hydronic toekick heaters existed; the quotes I got all mentioned 'electric fan toekick heaters', and I didn't want to go that route. When discussing with my contractor last evening, he was very supportive of the hydronic solution; now I just have to make sure that the unit will fit under the 'door' side of my vanity (will need to access it for service, so it really shouldn't creep into the drawer side of the cabinet.) Fingers crossed! Mongo, thanks! I'll do my homework on the BTU calculations; thanks for pointing out what to look for. Lynneblack, thanks for the vent/fan/light combo idea. I've read on the boards that the Panasonic is a great unit, but one of the two items I'm keeping from the current bathroom is my Nutone melon vent fan/dimmable light.

First timers need to know what to look at. First timers in heated floors need to know that heat is related to your insulation and your building's structure. The thing to consider (and to express in your first post) is your subfloor material, how well insulated it is from your building envelope, and what you will be expecting from a warm floor. It is entirely possible that you will get a great warm floor that heats up fast, and it is ALSO possible that you will get a weak warmth that underperforms. The choices you make about everything other than the membrane are the factors. The membrane is "topical", on top, above the heated floor. The specific membrane you choose is not relevant to any discussion about heating. Focus on the bigger subjects.

I think ours is Laticrete brand. Our shower is curbless and the radiant floor heat covers wet and dry areas. I had already perused the John Bridge tile forum where they talk a lot about radiant floor heat so I knew I could have it under the wet area as well. My contractor did ask me initially so this probably helped him decide which product to use. And we LOVE the open shower concept. No door to mess with. Adds a lot to the relaxation of a shower. This post was edited by elphaba on Mon, May 27, 13 at 23:34

no matter whether one person or a number think that it won't "really" heat an area of thicker concrete, just do it. How much is "really" in scientific terms ? How much is "really" in subjective terms? It doesn't matter. It's your house. Any additional heat is good not bad, warmer not colder, more comfortable to users and not less so. Heat transfer happens. The thicker parts like the sloped floor or the curb still DO warm up, and this can be proved with measuring instruments (thermometers), and it can be FELT by people who feel the temperature differential (note 1) and later you might say it isn't "much" of a difference. So what. Heat / cold is a funny subject. A lot depends on perception of differences, not absolutes. Why deliberately plan to have a cold place in your house? Why make it the shower? No need to overthink it, no need to ponder, no need to pay a professional for his time to discuss this with him, just do it and only reasonably so, because we do all agree that at some point one does have to stop perfecting heat distribution. If you want to read more, see wikipedia : heat transfer ; read one article and see the links to others. You'll see that heat always spreads into cooler areas no matter how much Mass is in the way, no matter how slow the spread if there are insulators. Heat transfer Heat sink Conduction (heat) -- Heat conduction Thermal mass Thermal conductivity Thermal insulation Building insulation Building construction Thermal contact conductance Thermal contact note 1: the temperature differential is a gradient in a vector field, if you wish to use math to explain it. If heat were like particles or electrons, then a temperature gradient would produce a current of heat particles flowing to the cooler area -- this current is the difference you feel, continuously. One can choose to ignore it, consciously or automatically. Or you can design your radiant heat to reduce the gradient so there is less current flowing across the shower space from the get go. This is comfort.