Hi mongo- Thanks for your thoughts. I agree that the small pump and loop would be best, but I think too difficult at this point. Here's the situation: bathroom is over a VERY shallow crawl space (used to be about 5" between joist and dirt, but when we gutted the space my DH spent many sweaty days shoveling the CLAY soil out through a hole we cut in the wall. Ugh!) The only access to underneath the floor would be if we removed the tub and cut out the subfloor. Even then, there's only about 18-24" under there. The supply used to run in the exterior walls, and froze last winter. We (DH) rerouted the supply through the attic space (one story home). He ran it right along the sheetrock, and insulated the cold lines with that grey split stuff against summer condensation. Then he created a sort of "tent" or "tunnel" over both sets of pipes with that aluminum faced bubble-wrap type of insulation. All foamed tightly in place. On top of that is two layers of pink finerglass batt. It's certainly better insulated than it was before. Pipe is 3/4" PEX. At the interior bathroom wall, it turns down to supply shut-off valves accessible in the bathtub control panel. From there it runs under the bathroom floor, on the warm side of rigid insulation foamed tightly to the joists. I actually just got off the phone with a tech guy from one of the tankless on-demand companies. He says that the tankless option is do-able, but we'd need such an upgraded model that it wouldn't be worth it for the 30 seconds or so we'd save waiting. The only place to put it would be in the closet by the shut-offs (since that's the closest access we have). And since there's no way to add it to the sink-only plumbing (I don;t think: see below) it would have to be sized for the GPM the shower demands, otherwise even when it's not heating the water, since the hot water is running through it, it would reduce the flow at the shower too much. Since we have a showerhead AND handshower that sometimes run simultaneously, that would not do. And the higher GPM models are just too pricey. I was thinking I *might* be able to swing $125 or so by next fall if I saved. not $500 certainly. Our bath remodel and some medical emergencies have really drained us, I'm nervous about even buying fuel oil for the rest of the winter! The only space and access at the vanity itself is a 4" space between the wall and the back of the drawers. The vanity is all drawers, and was custom made, so we can't/won't modify it. I don't imagine any of the cheap heaters are like 3" deep? So, I will probably have to learn to live with it. Not a huge big deal. The shower and tub take very little time to warm up (higher GPM I guess) so its really the sinks that are the issue. We'll probably just live with it. Thanks!

floor heat is not hot enough to warm your clothes in the way that was mentioned in the first post. it is ok to warm a closet floor too. There is no danger. when you go see floor heat companies' web sites, you will see that they often place the heat cables in the middle section of the floor and not around the perimeter:: this is one way to plan it out well, so that you are not spending more and not putting heat into furniture (or boxes). BUT, the amount of heat energy is so minimal that it makes no big difference if some of the furniture base is resting on heated sections of floor. However, this statement might be untrue in one case or another, and if so, then the heat will build up a bit more than expected and perhaps cause some form of problem (like, just imagining, e.g. a stronger glue smell coming from cheap furniture). So, the companies are not going to overstate the case and advise you to install heat cables underneath fitted furniture that has closed-box bases.

Wow. Thanks everyone for your suggestions. Bishop8 - it's a fire hazard to have towels too close to a baseboard heater. I believe the distance must be 8" between the top of the heater and the bottom of the towels, which should be fine, except for people and kids who fling the towel over the bar so that it slides down almost to the floor. Billl - yes, that's exactly what I want to do, heat the floor surface not so much the air. You said infrared heater. I think of those when I think of the old-fashioned bathroom ceiling heaters you still see occasionally in motels. Are you saying they make infrared baseboard or wall heaters? Do you know any brands you could point me to? Davidro - as I mentioned in my OP, I am not going to pull up floor tile, because I would never be able to re-do the marble floor tile to match the existing marble tub surround and shower walls. Also, this bathroom is an interior ensuite to the master bedroom - i.e. they share the floor structure, and there are no outside walls in the bathroom. But the bedroom floor feels fine, because it is not marble. It is the marble that is the issue, not the floor structure underneath the marble. Birdgardner - I thought of the attic too, which is actually little more than a crawl space above the bathroom. I checked up there again, and it is quite well-insulated. As I mentioned in my OP, you can feel the marble through slippers, and I should have mentioned they are the thick slippers which are normally warm! I am thinking of chucking the whole idea of a heater (and the cost) and getting a thick rug. Maybe I'll post a new thread on this Forum to ask for suggestions for bathroom rugs. Only problems with a rug is that it won't cover the entire standing area, and I am not a fan of rugs in bathrooms because they are dust/hair/powder/sprays traps. I guess there is no ideal solution, but I must weigh the pros and cons of all the solutions provided here. Thanks so much!

I installed Nuheat in the past and found it to be SO longer to install compared to mesh system ( you have to put mortar twice!). They also are very expensive! I tried Warmly yours, Suntouch and Thermosoft. They all are much easier to install. However, Suntouch and Warmly yours are far more expensive than Thermosoft. Warmly yours also does not make it here. It is made in India. I also found that customers are looking for No EMF products nowadays, since EMF can affect health and electronics... Warmly Yours and Nuheat have huge EMF, even though they claim that they don't... Get Gaussmeter from Home depot and check it yourself... I use Thermosoft now and all my customers are happy for years already with the price, quality and NO EMF thing they have. Their product is of very good quality, good prices and made in States (not in India, Poland or China... ) . So far, I also had very good customer service with them and extra discounts for the repeated orders.