Tipi with wood stove and radiant heat

Leighanna

Hello!

I'm in the process of making a tipi my home. It's all trial and error and imagination realized at this point.

My idea is to wrap pex lines around the flue or body of the stove and feed into the floor. I will likely go with a concrete or earthen floor, but the weather is too cold and variable out here in Montana to trust concrete right now. The whole slab could freeze and it's not unlikely that cracks would ruin pex lines. But the canvas is only a week or so out, and I'm ready to live in it now.

My ideas is this: I can set up the pex lines in a spiral leading out and back into center of tipi, since that's where the wood stove will be. I'll translate to copper pipe to wrap around the body of the stove. I'm thinking that a small solar panel and water pump (making sure hot water doesn't feed into pump) could achieve this pretty easily.

What I'm wondering is.. Can I just put some good dirt over these pex lines and walk on it as such now? Mostly because I want any floor to be temporary and easy, so I can have an earthen floor this summer. And because it's cold and a radiant floor that's so grounded and close to earth sounds incredible. I'm not sure what the thermal mass of dirt is and I likely wouldn't make any of this high tech, with controlled systems or thermometers.

Let me know if you have any ideas or tips or questions. Thanks

Ironman

I see several potential problems:
1. Wrapping tubing around a flue pipe may NOT transfer sufficient btus to heat the structure.
2. Wrapping tubing around the flue may also cause the flue gasses to condense and also produce an unwanted build up of creosote in the chimney.
3. Placing the tubing directly in the ground with no insulation under it or around the perimeter will cause the vast majority of heat to be transferred to the ground and not the structure.

Has a heat loss calculation been done to determine the load?

Zman

This sounds like an interesting project.
Wood stoves typically waste most of the heat created, so finding a way to reclaim and store it in the slab would be advantageous.

I guess the first question would be, how permanent is the tepee and what is the budget (keep it general per site rules)?

Concrete with insulation underneath would be ideal, as would a fairly elaborate control setup. This, of course, costs money. I could see a scenario where the stove could be fired for a few hours a day and provide nice even heat and domestic water heat.

You need to be careful not to pull too much heat out of the flue gas as it will cause creosote buildup and destroy the flue. You also do not want to put super hot water into a concrete slab as you can crack it and overheat the space.

If this were mine, I would start looking for a very small wood stove with an integral coil for HW. It would be cool if you could cook on it as well. It might be possible to retrofit an old cabin stove.

Leighanna

To be honest I wasn't really planning on running the flue pipe all the way up the tipi, I'm using an existing free stove that I believe has a small sleeve on the top. I'm considering that running lines around the body (maybe even through?) may work better. As is, I'll likely try just living in it on dirt and a wood stove, and see how it goes.

I can get concrete very cheap if not free, so that's not so much of an issue as the cold weather. And certainly I understand and agree that a lot of heat would be lost with no insulating barrier. I have done no heat loss calculation.

It does seem like a rudimentary approach, but people have been living this way with just a fire in the middle and no radiant heat concrete slabs for a long time. Any ideas for a more natural approach to insulation than blue board?

Jamie Hall

A lot of people lived for a lot of years in tipis -- or other structures of similar thought -- with just the fire, as you note. Nothing wrong with that at all.

You're not planning on taking the flue from the stove out of the tipi? Just ending inside, perhaps with a Plains Indian type flap arrangement at the top? That works too -- otherwise, you're going to have a major smoke problem and, depending on the wood you burn and the stove, a possible problem with hot cinders (see below).

As to insulation. Unless for some reason you really want a warm floor -- or concrete -- plain earth isn't bad. Plain earth with straw on top (but mind the potential fire hazard...) is much better. Even better is the plain earth in areas where you will be mostly standing and working, such as food prep. (easier to clean up) and fur where you might want warmth around your feet

In any event, mind your siting. The last thing you want is any possibility of rain or snow melt getting in. Ideally, if this is to be a semi-permanent arrangement (tipis usually weren't -- they were the Plains Indians approach to travel trailers!) I'd suggest building up the pad for the tipi a foot or so above any surrounding ground.

Gordy

Do what you can until the weather breaks. When it does pour a raised slab with 2” xps under it, and do 2” xps around the edges. That will give you some thermal storage in the slab that won’t go bye bye when the stove goes out. How you heat the fluid is experimental, and what SAFELY works with in your budget.

Gordy

Sounds cozy.

hot_rod

I worked with a plumber in NW Montana that lived in a tipi. He heated with a basic campfire, adjusting the smoke flaps to keep the smoke going out. Other than his clothes smelling like smoke, he was always warm and comfortable. When the fire was burning

nibs

We heat our hot tub with a wood stove with a loop inside the firebox, works fine and does not need a pump. The tub is open to the air so it does not matter if the water boils in the stove.
If you deal with the possibility of boiling the coolant, and use large enough radiant piping, you may be able to dispense with a pump.
Note that cooling the firebox and or flue, will cause difficulties with draft and, unless your firewood is very dry (under 18% moisture content), creosote.

Leighanna

Jamie: The tipi will have smoke flaps at the top, and since an open fire’s smoke is drawn up naturally, I feel fine about trying out the stove with no flue. It just seems like an eyesore to me. We’ll see though! It can all be changed.

Agreed on drainage, I think I will build it up. I have access to free sand and dirt and probably gravel… Sand and gravel would do well with any draining but I bet with raising it up I wouldn’t have any issues with good old fashioned dirt. No one wants sand in their socks.

I think the summer will be a lovely time to pursue floor ideas. I'm drawn to the idea of radiant heat in an earthen floor, and maybe some sort of clay burrito bed with radiant heat. Cozy. Fur and wool and horse blankets could do some good too.

Ahh, who doesn’t love to smell a campfire on them. Thanks hot rod, that was great encouragement.

Nibs: What size of radiant piping do you use, out of what kind of tubing? How far away from the stove would a bend/solder need to be? How large is your wood stove? I’ve thought that there must be a way for the fire to pump the water, is that basically how it works? The pressure of the boiling water moves itself along?

I’m curious as to what the hazard of creosote is. From what I understand it’s just a buildup of soot, more or less, that a chimney sweep would clean out? Can’t I just clean it when it gets dirty? Is it harmful in any way?

SuperTech

Creosote causes chimney fires. So yes it's harmful and hazardous.

Jamie Hall

SuperTech said:

Creosote causes chimney fires. So yes it's harmful and hazardous.

Quite. Creosote isn't just soot; it's sort of a tar. It has to be heated fairly hot to catch fire, but when it does it burns very quickly and very hot. It will crack masonry chimneys -- and burn right through the side of steel stove pipe. Not at all what you want inside a house, never mind a tipi. And since it burns hot, it creates a terrific draught -- I've seen chimney fire flames 20 or 30 feet out of the top of a chimney.

KC_Jones

It also depends on the wood you burn, burn soft pine and it can make creosote no matter what. Hardwood is your friend.

Creosote, yes it's soot of sorts, made up of carbon. You know what coal, and charcoal are made up of? Creosote should be viewed as fuel IMHO.

Gordy

As far as creosote build up. Intermittent Hot fires, hardwoods, and short chimney heights are your friends.

Depends a lot on your wood burner of choice also.

In your scenario with the chimney in the conditioned space that flue will be less likely to get build up so long as you do the above.

Lance

I thought the real purpose of a tipi is its mobility. If its not going to be mobile, I would build differently. Is this a camping retreat for the rich? You seem to have a lot of luxury here. I would think radiant floor with a water tank heated by the stove. Puts heat where it does the best will be well worth it. My tent was only 7 feet long & 3 feet tall at its apex and body heat was all I had. Build small uses less resources. Interesting engineering challenge.

ChrisJ

A good friend of mine tried wrapping a bunch of soft copper pipe around a wood stove pipe to heat a heat exchanger in his furnace.

It worked great until a pump failed which caused his pex tubing to fail which caused the water that was left in the copper tubing to turn to steam.


He was woken by a very loud very scary shaking banging steaming monster wrapped around the stove pipe in his living room.

He never used it again.

hot_rod

Gordy said:

As far as creosote build up. Intermittent Hot fires, hardwoods, and short chimney heights are your friends.

Depends a lot on your wood burner of choice also.

In your scenario with the chimney in the conditioned space that flue will be less likely to get build up so long as you do the above.

Moisture content of the wood should be noted also. A small inexpensive moisture meter is a good investment, or an ohm meter. Typically I try to season the wood for 1 year before burning.

Certainly a CO detector would be a wise investment.

Intplm.

@Leighanna. You surely want to do this safely.
Something you can research for is a residential flue pipe economizer.
They have been in use for many years commercially. I am not sure if they are made for what you are trying to do as your situation is quite different.
There are many safety concerns mentioned here.
The byproducts of combustion must exit the tipi safely so no one gets sick or worse.
Maybe try to find a residential economizer? Do some homework. See if you can go from there. Safely.

Gordy

it’s deff

hot_rod said:

Gordy said:

As far as creosote build up. Intermittent Hot fires, hardwoods, and short chimney heights are your friends.

Depends a lot on your wood burner of choice also.

In your scenario with the chimney in the conditioned space that flue will be less likely to get build up so long as you do the above.

Moisture content of the wood should be noted also. A small inexpensive moisture meter is a good investment, or an ohm meter. Typically I try to season the wood for 1 year before burning.

Certainly a CO detector would be a wise investment.

Yes moisture content. I left that out considering the circumstances. Pretty hard to maintain low moisture levels with wood stored outdoors. Having an indoor store is always nice. Seasoned a year is a good rule of thumb, but that depends on how it’s stacked, log sizes, type of wood etc.. most people try to burn what it is so long as it burns.
Burning hot usually keeps the flue clean, or at least no glazed creosote build up.

nibs

To heat our hot tub we use a barrel stove which we modified / insulated to keep as much of the heat inside as possible.
The in fire water pipe is 1 1/4 galvanized, but if you can afford it you can buy stainless loops. You must not burn a fire with dry galv pipe, noxious gasses will be given off. ours is all out doors so not too big a problem. we made an M shaped loop with street ells and threaded pipe that enters the back of the stove and
Passes over the fire, to use thermo/syphoning you would have to minimize headloss. You must build a system that will tolerate boiling/steam creation or you could really hurt someone.
Our system operates with about 18" of head, above the fire box and the hot water is discharged into a pipe that is submerged, so if the water is boiling or a steam water combination, no worries, just do not touch the pipe.

Jamie Hall

I can't quite figure out how one could rig things up for themosiphoning with the heat losing element below the heat creating one... works fine when the heat losing elements -- the radiators -- are above the heat creating element -- the boiler -- as witness gravity hot water heating. But the other way around? What force is there to drive circulation?

Gordy

I had that thought.......he’s saying thermosiphoning. We are thinking gravity flow. Same?

Intplm.

https://books.google.com/books?id=9oY3AQAAMAAJ&pg=PR26&lpg=PR26&dq=country+life+in+america+smoke+pipe+economizer&source=bl&ots=IN7PIfdMUw&sig=ACfU3U1miD-2wEmxfzKaM8BRRXoPvYlxCg&hl=en&sa=X&ved=2ahUKEwjU98He883gAhVlnuAKHUqgD2cQ6AEwDnoECAkQAQ#v=onepage&q=country life in america smoke pipe economizer&f=false

@Leighanna Take a look at this attachment and see if this is something that would work for you. If you use the proper materials you could add a coil of copper tubing to the inside pipe.
Be cautious as to how you do this!!!!
You say you were not considering running the flue pipe out of the tipi. You should reconsider that. You are changing the dynamics of your living area. Best to keep things safe.
Hope this old article can give you some ideas on how you might proceed.

Gordy

What they don't tell you is that by cooling the smoke pipe you create a breading ground for creosote build up in the smoke pipe. it also effects draft. Does it work? Yes with unintended consequences.

Voyager

If this is going to be a permanent dwelling, I would consider having a more substantial masonry heater in the center of the teepee. That will burn your wood more efficiently and provide more even heat in between large fires.
https://insteading.com/blog/masonry-heater/

I am not sure about natural insulation, but probably the best would be hollow clay tiles in a few layers under the dirt that will trap air and provide some insulation that way.

Intplm.

@Voyager. Thats an Idea ! I'm wondering if the stack temps will be high enough?

ChrisJ

Jamie Hall said:

I can't quite figure out how one could rig things up for themosiphoning with the heat losing element below the heat creating one... works fine when the heat losing elements -- the radiators -- are above the heat creating element -- the boiler -- as witness gravity hot water heating. But the other way around? What force is there to drive circulation?

The Ford Model T used thermosiphoning and it's radiator wasn't above the engine.

My understanding was hot water went into the top of the radiator, cooled and "sunk" to the bottom of the radiator. This pulled more hot water in the top.

Voyager

And Model Ts were famous for overheating. My grandfather told me many stories about that.

ChrisJ

Voyager said:

And Model Ts were famous for overheating. My grandfather told me many stories about that.

Not really the point....

Gordy

Thermosiphoning by definition is the same as gravity circulation. The model t example worked okay, but not well.

Voyager

ChrisJ said:

Voyager said:

And Model Ts were famous for overheating. My grandfather told me many stories about that.

Not really the point....

It is entirely the point. Thermosiphoning is a very slow way to transport heat unless you have a huge volume of fluid.

Cars have water pumps for the same reason that modern hydronic systems have pumps.

Gordy

If elevation is in the system it works quite well. Ask the dead men .

What makes it not work well is when the elevation difference, and temperature difference is closely matched.

In the case of the model T cooling system, the radiators were huge by comparison of a water pump cooling system. There was a slight elevation from the top of the heads to the top of the radiator. The issue was the bottom of the radiator where the cooler denser water would be was lower than the heads. It worked just ever so slowly.

Jamie Hall

Think about what @Gordy wrote, and think about this application. In the Model T, the water in the heat source could move up into the top of the radiator, where it was cooled (after a fashion), became denser, and moved down in the radiator. Then as the water in the engine was heated, it moved up... and so on.

In the application under discussion here, we have water in the heat source which becomes heated and less dense, so wants to move up. But... up to where? The pipes for cooling it -- if it could get there -- are lower, under the floor. The warm, less dense water, will just stay where it is, and the cold, more dense water will also stay where it is.

Sorry.

Gordy

It’s the best they could do unless the radiator was in the line of sight for driving, or on the roof.......

Voyager

Jamie Hall said:

Think about what @Gordy wrote, and think about this application. In the Model T, the water in the heat source could move up into the top of the radiator, where it was cooled (after a fashion), became denser, and moved down in the radiator. Then as the water in the engine was heated, it moved up... and so on.

In the application under discussion here, we have water in the heat source which becomes heated and less dense, so wants to move up. But... up to where? The pipes for cooling it -- if it could get there -- are lower, under the floor. The warm, less dense water, will just stay where it is, and the cold, more dense water will also stay where it is.

Sorry.

Don’t be sorry. We will get you straightened out.

You seem to be suggesting that the area being heated needs to be above the heat source. I don’t think that is correct. Let me offer an example for consideration.

Suppose you have a large swimming pool you want to heat. Suppose your heat source is above the pool. Now plumb a large pipe, say 6” in diameter in the form of an inverted U that exits one end of the pool and returns at the other end and purge it of air. Place the heat source so that it heats only one side (vertical leg) of the upside down shaped U pipe. Do you contend that no circulation will occur and that the pool temperature will not increase?

Gordy

It will siphipon, and heat the pool. Eventually..... the denser cold water in the pool will pull the less dense water down the pipe, but you will use a lot more fuel to do it than if the heat source was above the pool. The higher, and larger the temperature differential the faster the flow.

Voyager

Gordy said:

It will siphipon, and heat the pool. Eventually..... the denser cold water in the pool will pull the less dense water down the pipe, but you will use a lot more fuel to do it than if the heat source was above the pool. The higher, and larger the temperature differential the faster the flow.

Precisely. That was my point in regard to the Model T overheating. Thermosiphoning will work in a configuration as was described earlier, but it will be very slow and ineffective and hence the reason for using a pump. If the Model T had used a water pump, it would not have overheated in most circumstances.

Jamie Hall

@Voyager -- yes, that siphon system would indeed cause circulation. Quite right. The difference in density which drives the circulation is between the heated water in the one rising leg and the now slightly cooler water in the other, descending leg. Provided that the cooler water in the descending leg was warmer than the water in the pool, you would -- eventually -- get the pool warm.

However, as I understand this application, the heat source -- the stove -- is at or near the highest point of the system, and pipes go down from there to the radiant floor, and from the radiant floor back up to the stove. I suppose, thinking about it, that if you arranged the piping so that you did, in fact, have a riser from the stove and then, at some distance, a pipe going down to the radiant floor and then back up to the stove, you could drive a thermal circulation that way. But not if the heat source -- the stove -- is at or near the highest point in the system.

You could, however, probably design a heat pipe system, using an appropriate working fluid and suitable wicks... no moving parts... heat pipes are interesting systems. Or possibly a system using ammonia adsorption (a reverse of the gas fired ammonia refrigeration systems). Hmm...

Or use a small pump with solar PV and batteries.

ChrisJ

> @Voyager said:
> It will siphipon, and heat the pool. Eventually..... the denser cold water in the pool will pull the less dense water down the pipe, but you will use a lot more fuel to do it than if the heat source was above the pool. The higher, and larger the temperature differential the faster the flow.
>
>
>
> Precisely. That was my point in regard to the Model T overheating. Thermosiphoning will work in a configuration as was described earlier, but it will be very slow and ineffective and hence the reason for using a pump. If the Model T had used a water pump, it would not have overheated in most circumstances.

You need to do some research on the model t my friend. Many had water pumps.

And I believe the thermosiphon design did fine under most conditions.

Gordy

problem is any reasonable lengths of small diameter tubing used for a radiant application would hinder flow even more.

Me dig um hole for fire in ground. Putum heat exchanger in bottom of fire pit. Watchum hot water rise, and cold water fall like running deer from great white hunter......sorry had to do it

Voyager

Personally, in a teepee with wood heat, I would give up on the radiant floor idea entirely and build a circular shaped masonry heater smack in the middle and burn a couple of hot fires each day, one in the morning and one in the evening.

I have a masonry heater in my home and they work great. Mine is not large enough to heat my home as my home is a little larger than your average teepee, but if you stay within 15 feet of the masonry heater, it will keep you pretty warm even 10 hours after the last fire.