Underfloor heating from compost?

[RawMan]

Hi everyone,
I would like to build a small wooden house, or a yurt, or something along those lines. I had the idea to build it on a platform and have large slidable boxes of compost under the platform, to act as a constant heat source. I live in Ireland, so it's pretty cool and wet. I searched a bit on the net, but I couldn't find any information about this kind of system.
Has anyone ever tried this? I don't see why it wouldn't work, but I'm a newbie to all this, so maybe I'm overlooking something.
Any ideas, resources, comments would be appreciated!
Thanks,
RawMan

[Richard on Maui]

It would work, but it would be a real pain in the arse, I reckon... Might smell a bit too? Yeah, yeah, I know, a proper compost doesn't smell bad, and the USA is the worlds greatest democracy... (insert rolling eyes guy)

[Jim Bob]

Compost will typically reach temperatures of 50 deg C or so. This heat has to be transferred into your house somehow. You could do this in two basic ways, I would think.

The first is to have the exhaust vents of compost running directly into your house. This would be stinky.

The second is to have a system of ventilation shafts running from the compost boxes under the floor, heating it. They'd then run up the walls and to the roof. The problem here is that air is such a good conductor of heat - most of the heat will rise up and away from the house before it can transfer through the floor.

The other problem is that normal compost piles are mostly aerobic - they use oxygen. If you want to keep the thing's heat, then you need to close the boxes, as people do for humanure (composting your shite); you close off its air supply. If you keep it closed, then the compost becomes mostly anaerobic - the reactions don't use oxygen, but produce it. These reactions are the stinky ones.

I think that the most warmth you'd get from this system is when you're dragging the boxes out from under the house to fill and turn them. It's a fair idea in principle, but the practice doesn't look good to me.

On the other hand, you could do other things like have a seedling box sitting on top of your compost box - a little bit of heat there would help them in the cold Irish climate. The seedling box keeps the rain off the compost, keeping it dry and helping it be aerobic, and the pile warms the seedlings slightly.

[hedwig]

I used to work (a bit ) with composting plants. One of the biggest problem was the construction material. Because the compost and its bacteria will root nearly everything away, even stainless steel (I think you don't want to rebuild your house frequently?). This and the smell (and I reckon the gases are not very healthy either) are the cause why no one does it. And you need heaps of compost to heat your house. What you can do is making a compost heap well away from the house and try to transport the heat in the heap. Compost attracts rats as well, especially if it's warm and cosy and outside it's cold.

[RobWindt]

"What you can do is making a compost heap well away from the house and try to transport the heat in the heap"

Dunno how well this works in real life but looks like it's worth investigating http://www.daenvis.org/technology/Jeanpan.htm

[Douglas J.E. Barnes]

How about a straw bale home with an attached greenhouse and masonry stove? Or a separate building housing the compost and running pipes through the compost for heating?

[RawMan]

Thank you all very much for the replies.
Perhaps running water pipes through the compost and keeping it away from the house is the best idea? Is it necessary to turn the pile regularly to keep it hot/warm?
Or I could easily use a simple stove for heating, which I probably will resort to! But I just like the idea of heating without smoke.

My brother is currently renovating an old house and the biggest problem he faces is what kind of heating system to use. He is interested in masonry stoves, but knows little about them. Does anyone have any good resources on masonry stoves, or other effective solutions. He is a carpenter and has building experience (moreso than me) so he wants to build the stove/heating system himself, if possible.

I'm researching both of these topics online, but if you can help me out and save me some time, that would be nice! He wants to move into this house as soon as possible, and ordering books on the internet would be a bit slow - he wants to be finished and living there by the time the books would arrive.

Thanks again! :)
RawMan

[Douglas J.E. Barnes]

If you've got a big pile, it will retain heat and won't need turning. Municipalities that compost large piles of waste have to face the problem of piles combusting. About a month ago, I picked up some from the city of Toronto and it was still very warm despite having been started last year.

[Ev]

warmth and humidity are a termites friend in Australia I would not put anything under my house that created a better environment for termites
Do you get these little ants where you are?

[Douglas J.E. Barnes]

They're not usually trouble in either Toronto or Tokyo.

[Andrew Clarke]

Hi RawMan and all

I think I may have a solution, which is kind of along the lines you're talking about. This is to use a large pile of woodchippings from your local tree surgeon or bark peelings from a sawmill, assuming you have vehicular access to your site.

I'm fortunate in having a free supply of woodchip albeit in small quantities. One small truck load I had delivered last winter remainined warm in the core for ages... and remember that I'm only just across the Irish Sea and the latter part of this winter gone was really cold and wet at times.

There's a fantastic reference detailing this system:

Pain, Jean & Ida. 1972. Another Kind of Garden.

I bought my copy a few years ago from Permanent Publications, they may still have it.

This self published small book recounts the authors' experience with shredding forest brush in the south of France; by pumping water through layers of plastic pipes which are placed through a prupose built heap the size of a `small garage` they were able to secure free hot water/central heating for many months! Plus great quality compost and biomethane.

Unwanted guests/pests could be a problem with compost but maybe you could rig up an underfloor hot water system/radiators for your yurt using the brushwood method? I keep meaning to find out what's happening with this method, they were busy refining their system while writing the book, I'm sure there are some contemporary researchers with interesting findings. Has anyone any idea?

I'm still playing around with ideas for incorporating some kind of heating system from brushwood here, only problem is the distance from the pile/composting area to the house. It may well be incorporated into an underfloor greenhouse heating system.

Anyway, I'd be interested in finding out how you get on.

Best wishes

Andrew

[Paul Cereghino]

Old topic but...
The compost pile is just another heat source like fire or the sun, if you're looking for a low stress design, how about a trombe wall like for passive solar gain. Build a section of the north wall as a thermal mass that can be used to transfer heat from outside to inside using conduction. When it gets cold have a local tree chipper dump a load against the wall, or build a nice pile if you have a manure source. While it simmers you get a little thermal gain. When it cools you have insulation. Come spring you have mulch. A problem would be that if you don't use the wall you have a source of cold for your house.

The pile with pipes idea could use a thermo siphon to move air... pipe from bottom of house goes through the wall, up and back in higher. The heat of the pile heats the air in the pipe, causing it to rise creating a current.

Using big piles of new wood chips makes a nice smelling heap.

[sweetpea]

Raw man, beware of methane being flammable! Your house will have pilots lights, perhaps? Or even lights from candles, smokers, etc.

You would need a LOT of compost, which invites all the microbial and insect critters mentioned already, and it would put off potentially dangerous methane. Methane doesn't hurt to breathe it, unless it replaces the oxygen, like on the surface of Mars, but if collected in an enclosed space is dangerous !!!

What about passive solar? Or perhaps if you've got a lot of cloudy weather, taking advantage of the Earth's constant 50 degree temperature down below frostline by putting in piping that goes down into the earth and allows that constant 50 degrees to come back up.

I'm not finding a link right this second, but I think in Canada they are incorporating this into some housing. :)

[Dylano]

hallo there, I've been building a project that uses woodchips as a heat source to heat a polytunnel in cornwall england..
It's only in it's infancy, but the tunnel frame is up, the heating pipe is almost finished, and a massive load of woodchips was delivered today!
So if you want to keep an eye on what i'm doing check out:
http://lowarthbrogh.blogspot.com[/u]

This is a big step for me in regards to growing on such a scale, and constructing a home-made polytunnel. Any advice/comments would be appreciated.

A thing I keep wondering about now is whether 20 tons of woodchips would be more efficently used by burning in a stove or by fermentation.

On one hand burning gives high heat, when you want it. It also produces ash as a byproduct.
Fermentation gives you a lower heat for longer, gives you methane as a fuel source and of course tons of compost afterwards..
any ideas?

cheers
Dylan

[sweetpea]

Dylano, Interesting idea. Are you using fans to conduct the heat? what kind of wood chips? What do you do to them to get them to heat up?

Are you on the lookout for termites? I just had them invade my raised beds, and they found roots under my patio that is paved with bricks. They seem to be able to find their way through the smallest openings.

Burning the wood chips would be polluting, if you're concerned about that. And are you going to filter the air coming off the wood chips in case you get wood fungus in there, mold, etc, since they would need to be damp to heat up? I've had all these things happen, but not while I was using them as a heat source.

I'll check out your blog! :)

[Dylano]

Hallo,
there will be hot water in the pipes, which should conduct itself around the tunnel. The woodchips are a mixture from a local green waste company. As far as i know they need to be soaked in water for up to 2 months to really get the fermentation going.
we have no termites in cornwall lucky for us!

By using the pipes, i intend to avoid damp/mould etc. in a perfect world i'd also be tapping the methane to use asa fuel source. but small steps first!

thanks for the input..
Dylan :D

[davo]

Rawman, here's a suggestion for your Yurt thingy. It's quite involved, so I have opened a new thread for it, here: http://forums.permaculture.org.au/sutra27964.php#27964

Cheers,
Davo