Hi DJSPN,
No direct knowledge, but I have been at a concrete pouring party where they were installing the piping for radiant heat, but I have not been back to experience it in use.
At the pour they had leveled the forms all around, and then they used small "pea" gravel that was mechanically packed to level the space and to adjust the depth of the concrete. They used a gas powered packer on the whole area.
The concrete was to be thicker for the first foot or 18" (maybe 6" above the foam) around the perimeter, and thinner in the center part (I am guessing, but I would say maybe 3".
They put a layer of black plastic on the gravel, and then used blue foam to insulate under the concrete, I don't remember now, maybe the foam was 2" thick? I am sure the thermal break from the ground is very important. I think the blue foam was sort of like tongue and groove on the edges. They also had used the same blue foam cut in strips and stood it around the outside edge of the slab to totally insulate it from outside influence/exposure.
They had put stakes (1x2?) in the gravel that stuck through the insulation maybe 1" or 2", Some welded wire fencing was sitting/stapled on top of the stakes. The wire was to reinforce the concrete, so it needed to be suspended in the concrete, not just laying under it. They stapled the pipes to the top of those stakes with plastic bands they had cut from milk jugs. The wire also helped to support it.
The pipes made big "S" patterns across the whole space, and the pipe was not rigid pipe, so it did not really lay stiff, it was more like garden hose, but clear, and you could see some reinforcing cord was woven into the pipe. They told me the name of the type of plastic pipe at the time, but I can't remember it now, PECs maybe? I don't think it is important of not as long as it does not react with the concrete. I think the pipe would have been about 1" or 1.5" under the surface of the finished concrete.
They had cut some holes in the wires so the guys could walk around on the insulation, and I can remember asking after seeing a few places that their footprints were showing on the insulation, but they said that would be ok.
I remember talking at the time about needing the stakes to be set at a certain grade so it could be drained if that was necessary, but I don't remember if they had actually done it, or just saw the need for it. It would not be hard if you just added a frost free faucet at the lowest point. It could stick back into the concrete with no problems. I think this part would be easier with rigid pipe, it would not sag so much.
We were also talking at the same time about using an air compressor to blow out the
like the sprinkler guys do in cold areas to keep water from breaking all your pipes. I just can't remember what option they chose.
This has been been 6 or 8 years ago, and it was preparation for a straw bale house that a friend of my friend built back in Montana, and then he left the area a couple years later. I never saw the inside of the house, and only saw the outside before it was stuccoed, bales, wire and plastic.
I think it would be helpful to use as large diameter of piping as is practical and affordable, maybe 3/4" - 1". This should help keep your pressures down, but it would make the volume of water you would need to push more, so the pump might have to push higher volume at lower pressure.
I think I would try using a cheap fountain pump as a first try, I don't think a passive system would work as I think about the amount of pipe he had laying out on the wire screens, but I am not sure. I have not really thought about that, or looked at using any engineering to figure this out.
My parents built a (traditional) house in the mountains of western North Carolina, and installed the electric version of radiant floor
under the carpeting. It was comfortable and they were pleased with it, but that was back in the day when electricity was much cheaper. Western North Carolina isn't as cold as say, Western Montana, but it does get cold and snow, and the snow stays for a few days when it falls. East coast snow is all different from Montana snow. It has a high
content and settles a lot quicker I think.
At any case, it worked well enough for them with electricity, why shouldn't water work as well or better?
In addition, radiant heat from the floor helps with one of the big problems with yurts in cold areas. If you design your yurt to have privacy walls of any kind, those areas are blocked from radiant heat from a central source. You have to come up with some assisted air movement or secondary heat source to have heat to those areas to avoid cold spots. You can also have condensation problems where there isn't enough air movement.
I lived in Montana for 18 years with wood as my sole source of heat, and you do learn the tricks, but that was on the grid, where it was much easier to devise some method, something as simple as cheap box fan sitting on the floor blowing air out of the cold area made the warm air move much more effectively into the room since air temperature tends to laminate if it is stagnant, warm ears and freezing feet.
I can also relate just the opposite. I worked for a while (5 months) on the North Slope of Alaska (Prudhoe Bay) back in the day. Up there the situation is just the opposite. They lay out the piping for a freezer plant on the perma-frost, then they spray it with insulation, and then they pour concrete on top and build a building. Otherwise the heat of the building melts the perma-frost which turns to mud which slowly oozes out from under the slab and the building gradually sinks into the ground.
The refrigeration under the slab keeps the perma-frost frozen solid and avoids the problem, but energy is next to free there, natural gas is very explosive, so they sometimes just have to burn it to get rid of the hazard. They they used a jet engine burning natural gas to push a generator, and got rid of a problem and made good use of it at the same time.
Just my thoughts, not direct experience with using it. I am trying to be thorough and give as much information as I can remember, but there may be other questions if anyone thinks of them. Sorry that I tend to wander...
Rod
Rod
yurtlocker.com
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