Heating/cooling a dome on a slab or earthen floor

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Next year I will be preparing to build the geodesic dome I've ALWAYS WANTED, and had given up hopes of ever having (due to money problems). I haven't decided for sure what to do yet about heating. My choices are a masonry stove, which will take me (I estimate) about two years to build (that's two years AFTER the dome goes up, so I need some way to heat in the meantime) and hot water heat run through the slab somehow.

I'm not enthused with imbedding the water pipes directly in cement. In fact, I'm not enthused about cement at all, and would REALLY like to go with an earthen floor. THEN I wouldn't mind so much imbedding the heating coils because an earthen floor can be chipped out and repaired fairly easily. NBD.

I would still need a cement perimeter wall/foundation (extending below frost line, which is 18" to 24" here) for the dome, which will be constructed on a 5' knee wall (I need LOTS of flat wall space for bookshelves). The earthen floor would be constructed inside this foundation. The masonry stove would go smack dab in the middle of the dome, and would require its own foundation. I'm not sure how deep that foundation needs to be due to the fact that it would never freeze inside the dome (at least I hope to god it wouldn't!) so frost line is immaterial, but stability is still important. The masonry stove weighs 7 tons, that's a lot of weight that needs to NOT settle unevenly.

I can get an inline water heater (Aquastar) that will supply sufficient hot water for a system like this. Of course, if the power goes off, I have no pump, no water flow, ergo no heat, so I don't want to rely on this for heat, but I'm still interested in installing it for backup/temporary heat, and also because I'm thinking if I put a diverter in the system I may be able to run cold water through it in the summer (on its way to water the garden) to help cool the house.

I know this is kinda vague. Any ideas out there to help me pin down implementation, considerations I'm overlooking? JOJ? Got 2c to throw in?

-- Sojourner (notime4@summer.spam), August 05, 2001


I don't have alotta time now to go into any more depth but I don't think you wanna run cold water thru the floor tubing because you'll be inviting moisture problems on the floor.

-- john (natlivent@pcpros.net), August 05, 2001.

Hi, Sojourner, I've mentioned before, on various forums, how I've been kicking myself for not putting pipes in my slab at my new (ish) house. I personally LOVE concrete (cement is an ingredient in concrete, btw)

The idea here is that I could have routed all my irrigation water out of my well, at 52 degrees, here in Orygun, through the slab, cooling the slab, and preheating the irrigation water.

If I ever do another house with a slab, I'll certainly do this, since it's a win win deal imho, and there would be absolutely NO operating costs.

I agree; I don't like the idea of putting pipes DIRECTLY into the concrete, and for this reason, I'd put the pipes into (very cheap) schedule 125 pvc pipe, which is inside the concrete, and arrange things in such a way that a leaky copper pipe could be slid out of the pvc pipe from outside the building.

As far as heating the slab in winter, I know that this is thought to be a good thing to do. I honesty can't say. Intuitively it seems like a very fine idea, because warm feet = comfortable environment at a lower ambient air temperature, I would think.

I understand that the set up, with all the pumps, valves, pipe, etc, is pretty expensive. Sorry, I wish I had more data to share.

I you DO heat a slab, or in your scenario, a packed earth floor, it is extremely important to insulate VERY well around the perimeter of the house. When you get to this point, please feel free to contact me, either on a forum or at my real email address, which I believe you have, as moderator, right?

Also, if you're using hot water, or a solution of whatever in water, to heat the floor, you might want to consider a ground source (aka geothermal) heat pump to heat the water. Believe it or not, this type of heat pump is around 400% efficient. Sounds impossible, but it's not. The heat pump doesn't produce its heat, it "steals" or "pumps" heat from one place to another.

Good point about no heat if there's no power with this system. You might want to have at least a small wood heater, or something, for backup. Besides, the new wood heaters are way cool. Very efficient, and you can watch the flames dancing around in the firebox!


-- jumpoff joe (jumpoff@echoweb.net), August 05, 2001.

John, that's a valid concern. I live in an area with very low humidity (in the summer, anyway), and would not be worried about it, especially with a concrete slab. In a humid summer climate, especially with Sojourner's plan for a packed earth floor, it is worth a bit of head scratching.


-- jumpoff joe (jumpoff@echoweb.net), August 05, 2001.

I wish I'd known you wanted a geodesic dome. I've seen four or five just bulldozed here in the past year. A local and long since sold, resold and sold yet again bank built some as branches here in the seventies and eighties. With consolidations creating situations with two branches of the consolidated bank side by side, a number of those properties have been sold off and the buildings subsequently razed. I know at least one could have been had for the asking (and dismantling and hauling, of course). Oh, well... I guess that just goes to prove one man's junk is another man's treasure.

-- Gary in Indiana (gk6854@aol.com), August 06, 2001.

I've got a little more time now. I've got a radiant floor in the basement family room and shop and I love it. JOJ mentioned making sure the perimeter is well insulated and I second that. I'd also suggest insulating under the slab or floor, so the slab/floor is isolated from the cold earth beneath it. Another thing thats done is laying down a moisture barrier beneath the insulation.

I used plastic tubing that was specifically designed for radiant floor applications and did all the plumbing my self. It wasn't too big a deal but learn to sweat solder before you tackle something like this.

-- john (natlivent@pcpros.net), August 07, 2001.

John, according to the energy guidelines and requirements in the Oregon building codes, it is not necessary to insulate under the entire slab. The idea is that the ground itself has enough insulative value that it is only necessary to put insulation vertically, two feet deep, around the perimeter, or horizantally two feet under the outer edge of the slab.

This is a very simplistic explanation. A building dept, engineer, SOME good builders, or good construction manuals, can give further detail.

Careful: if the insulation in this type of construction is not installed correctly, you'll lose a LOT of heat out of the building. Make sure you do it right!


-- jumpoff joe (jumpoff@ecoweb.net), August 07, 2001.

OK, you've convinced me. I'm not going to try for the radiant heat in the floor thingy. Too complicated! Sweat soldering? I don't even own a torch! And I guess running cold water through there would be a real bad idea with an earthen floor. So much for the brilliance of my mind. LOL!

Now I'm waffling on the masonry stove/conventional wood stove issue. The result of that decision hangs on the outcome of my current waffling between the 24' and the 32' size dome. The 24' panels are smaller, lighter weight, and easier to handle, and the roof is closer to the ground. But the 32' dome has something like 75% more space, for only a little extra in building supply costs. Waffle waffle waffle - keep the syrup away from here, this is sticky enough already ...

-- Sojourner (notime4@summer.spam), August 08, 2001.

Finally! Something I can contribute to. We're building a 48' dome in NE TN (4 years already), and planned for a masonry stove so we have the foundation for it in place. The house is built on a tall 36" crawl space. Since we had neither the time or money for the masonry stove at first, we found a barrel stove and installed it on the foundation. It's a 2-barrel version with 55-gallon drums, and we had to put in a 24-foot stovepipe to reach the center of the roof. We've used this for 2 winters now, and even though it's not supposed to be a very efficient heat source, it keeps our house overly warm.

I think your idea of using circulating water to heat and cool is outstanding. Not sure where you're located, but even in this humid area, cooling the floor would make a huge difference in our comfort level. Heating a dome is way too easy, if you give some thought to air circulation. Heat goes up to the center and cooler air comes back down the perimeter. A ceiling fan helps.

If you can solve the problem of what to do when the power goes off, you'll be very comfortable.

-- Teresa (otgonz@bellsouth.net), August 12, 2001.

Sojourner I will be starting a monolithic dome in late October, it is so hard to design rooms in the round, well outside walls rounded, but the dome will start in at 7'6". I really did not want cement slab but that is the whold monlithic idea, all one big piece of concrete. I am looking for ideas for flooring to help soften the floors due chronic back pain, but I love the stained concrete floors, they are beautiful. Maybe I should just get used to not going barefoot in the house and get relief from shoes.

-- Deborah Patrick (theant00@yahoo.com), August 12, 2001.

Deborah and Teresa -

Oh goody, fellow domites! I'm waffling between the 24' and 32' dome size. I hope to go to this fellow's place and look at his 24' dome (he uses it as a workshop). Domes are very efficient to heat and cool, so I'm thinking that a masonry stove in this climate would really be overkill. If a barrel stove overheats a 48' dome, I hate to think what a masonry stove would do. I do think the condensation if I tried to cool with the infloor pipes would be a problem with an earthen floor. Also, I've talked to people who have installed these infloor systems and it sounds like way too much trouble, especially in an efficient building like a dome. So I've given that idea up. I'll take the woodstove I buy this fall (for the house I'm building now, which will become the workshop after the dome is finished) and move it into the dome when its finished. The PT will go into the dome as well. In freezing weather I can just shut the water off over there and only heat the building when I'm using it as a workshop, with propane heaters I've already got.

Of course this is all moonshine until I actually finish THAT building, and can move into it and get out of this camper. I can see the light at the end of the tunnel, and I'm pretty sure that this time it isn't a train ... LOL!

-- Sojourner (notime4@summer.spam), August 12, 2001.

Yea fellow dome lovers, check out www.zdomes.com. This is the guy that designed my dome home, 3000 sq feet. I should have airform inflation end of October and shell dried in by end of November, then we will have all winter to finish inside.

-- Deborah Patrick (theant00@yahoo.com), August 12, 2001.

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