[hvacman]

There are tradeoffs between floor slabs and crawl spaces. I've lived in both. I'll typically take a house with a "well-built" crawl space over a slab. A good wood floor feels so much better, with it's slight "spring", but they just don't build crawl spaces"right". Usually they don't put in a rat-slab for you are crawling around on rough dirt/rocks, etc and have insufficient clear height to comfortably crawl around under them. That said, at least in a pinch, you CAN access under the floor to inspect plumbing, pull new cabling, etc. With a slab, you may not know you have that small water leak in a bathroom wall until the bottom plat rots out and the wall literally crumbles. Plus try modifying a drain line with a slab floor. A royal PITA.

[efarmer]

The input wattage of the electric heater all turns into heat, in a fan forced one the frictional
losses of bearings, and motor core losses come out as heat as well but slower than the air
going across the heating element. In my case with gas furnace heat, I choose to run the thermostat
down to 60 during the night and do not want a fan forced heater whirring in the bedroom. I also
dislike the formerly common event of either of us going out to the loo or kitchen to allow the warm air to tumble out of the top of the door opening while cold air rolls in across the floor in response and
then wait for the heater blower to bring the air back to set point. So I use an oil filled heater run
on the 600W setting, (900W setting if inside to outside diff. is 55F or more) (5/7.5 amps at 120VAC) and put it right on the opening side of the door. This makes heat rise up like a passive air curtain, plus the oil has thermal mass and can use it's oil stored heat to dump back into the air and recovers faster than a fan forced heater. I have not done a bunch of science on this, just me in my undies, trying both, and feeling the thermal effects on my balding head as a precision temperature sensor when I stay in the rack and she goes out and comes back in. If you are lucky enough to have a snuggler, they can overcome much of the temporary discomfort, but I also have to stick my head under the covers and I worry about potential undesired heating effects via the Dutch Oven phenomena. So far this hasn't happened to me, because I am the guy, and we normally do that sort of horrible stuff, and then wonder why we are out on the porch with the dog, and no heat at all...

Another method, is if you have a cat, let him sleep in the bedroom a couple of nights, and when you wake up he will have found the best place where the drafts are minimal and the air is warmest. Then you move and sleep in that spot, but you have to kick him out after that, or else he will sleep in the next best spot and look at you up there snoring on top of the dresser like you are an axe murderer and make groans and plaintive noises all night to get even. It might even poop in your slippers, but they will generally stop short of scratching or biting, because they know they would risk getting fed the next day.

[Peak_Yeast]

I completely concur with Pops description of floor heatings virtues. I also plan to put floor heating in our bathrooms - that is waterborne floor heating not electrical.

For insulating floors I believe that polystyrene is the best choice - together with a moisture barrier. Personally I would not put concrete on top - but just a moisture barrier, aluminium plates for spreading the heat and then a "real" wooden floor. None of those glue-boards that IKEA loves or anything similar.

[AndyA]

micro heaters cut 87% off my electric heat bill
I am not a cold hardened person. Some people have suggested that I can tolerate the cold better than most. And there might be a little truth to that. But only a little. Without the little personal electric heaters, I get uncomfortable at 65 degrees F. In other words at 65 degrees F, my fingers get stiff and I cannot type. Plus I just feel so cold that I cannot concentrate. And that is with a sweater on.

My optimized system ended up with two parts: my desk and my bed. The key is that when I am inside, I spend 99% of my time at my desk or in bed. I have had people comment on how this does not solve anything for families, or for people that are watching TV, or for people that live a life that does not follow this pattern. I think that this position has a lot of truth to it, but is not absolutely true. I think that the key point here is that I focused on heating people instead of heating all of the air of all of the house. I think that this general approach can do great things for nearly every situation. Although it could take some time and thought for each situation. Maybe some situations will be able to save only 50%. And others will be able to save only 70%. Maybe somebody will have a situation where they were able to save 95%.

http://www.richsoil.com/electric-heat.jsp
The gist of the article is heating people not air, I think underfloor heating is terribly inefficient, but that's just my opinion, and the opinion of people who have had it, and stopped using it because it was too expensive.

[Pops]

Which people? I loved mine.

Of course the guy saved 87% of his bill, he only heated 13% of his house - he could have saved 100% by not heating it at all.

Hydronic Infloor heat is designed with - or at lest I designed mine - with zones that can be adjusted permanently or even with valves that operate on a thermostat or in the case of a concrete floor with a lot of mass, a timer.

[Peak_Yeast]

We have already saved 95%.

This old farmhouse was built in 1880. When I restored it I ripped everything inside out thus exposing the original walls.

They was not only layered with many types of wall-paper - but underneath all the wall paper was engraved and painted flowers/plants onto the bricks itself.

It suggested to me that 1 layer of brick was all the insulation the house had originally.

[vtsnowedin]

My daughter has a house with radiant heat in all the floors both wood and concrete. It works very well and can keep a room within one degree of target setting. That said I find it hard to believe that it is efficient to distribute heat uniformly to every square foot of every room. After all most rooms end up with furniture or cabinets around every wall. Do you really need to heat under your cellar work bench or the living room couch? I would think the first heat loop should be at least three feet from the walls so it heats the area you are actually occupying not your closets and dresser drawers.

[Pops]

One of the advantages of radiant is exactly that it heat things instead of air. When you sit down in that big Nauga-Leather power recliner it is all cozy and warm instead of cold and clammy as a dead nauga. Heated towell racks are quite a luxury and now that you mention it, there is a lot to be said for a heated underwear drawer. LOL

Since you can only get so much heat out of a loop of tubing before the water cools, you necessarily must use more than one loop to heat a large area or entire house, so each loop can be controlled and usually has at least a flow restricting valve. In fact there is nothing stopping you from making as many loos (zones) as you like. Each zone can be adjusted, tempered, timed, thermostated or what have you as much as you like. You could even plumb it so sometimes it transfers heat from one zone to another or gets heated water from a sunspace and sometimes a wood fire and sometimes a storage tank and sometimes a rooftop collector if you wanted. Since it is radiant heat it is naturally limited in effective distance as opposed to heated air which may or may not go where you want it.