Wood stove in underground emergency shelter?


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Old 12-05-13, 05:23 PM
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Wood stove in underground emergency shelter?

Husband and I are working on the construction of an emergency shelter for foul weather and power outages. During our planning, we are considering either a solar-powered electric stove, which would really eat up energy reserves, or trying to find out if a wood stove would be feasible.

If we were to use a wood stove, how would we ensure proper air flow for both the fire and ourselves, as well as proper ventilation for the smoke? Does anyone know if there is a way to make this work? A wood stove would certainly provide warmth light AND cooking capabilities along with a renewable source, but electric seems to be safer.

I have done some research on the wood-fueled cooking centers from prairie Sod houses in the US, but the sod houses were a bit less airtight than our storm shelter will have to be.

Any suggestions/insight would be greatly appreciated.
 
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Old 12-05-13, 06:25 PM
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Perhaps find a stove that has its own intake and exhaust. Gas fireplaces for example have a double vent which draws outside air for combustion and then vents it out the same pipe. Some gas fireplaces also do not need electricity to run except for a circulation fan which is optional.

The other option would be to have a make up air vent installed. Just make it small enough do debris can not get through.
 
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Old 12-05-13, 06:40 PM
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For that kind of a shelter I'd use wood or propane. Both store equally well and don't require maintenance. Due to the enclosed and restrictive nature of the shelter you probably wouldn't need to much for heat and you would keep the cooking to a minimum. I think I'd lean more towards propane.

You would have to address fresh air in as well as exhaust.

Years ago a friend of mine had an underground shelter. More like a bomb shelter. He had two lines that connected the shelter to above ground. One had a hand cranked blower for bringing in the fresh air. He knew that it wasn't really a bomb shelter as you would have to rely solely on stored oxygen.
 
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Old 12-05-13, 06:44 PM
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Actually the new trend towards air tight homes has looked at this issue in depth. What is required is what Tolyn is suggesting, a wood stove that draws its combustion air from outside. Being one who cooks on our wood stove during prolonged power outages, consideration must be given to the style you choose. Not all have sufficient flat space on top.

Google "passive house and wood stoves" or "Passivhaus".

One caution, don't plan on keeping a lot of wood stored indoors. Even dry wood will have a lot of moisture, not to mention creepy critters.
Bud
 
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Old 12-05-13, 07:08 PM
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Awesome! This is exactly the kind of information I was looking for.

Tolyn -- the idea is to have at least one fan for regular air circulation, and possibly another system for the stove. Our proposed design calls for ventilation vents shaped like an upside down "J", or like a candy cane, so that it keeps out rain water. Could a make up vent be used the same way?

PjMax, your friend's shelter sounds fairly similar to what Husband and I are planning. Completely underground on a hillside (also called earth-bermed) in order to protect from high winds, flooding, crushing debris, etc. We would like to use propane, but since he and I have both been through extended outages (I was in south bama/florida for Opal, he was New Orleans for Katrina), we know that stored propane can go quickly, and can be hard to find. Wood stoves would provide a more renewable form of fuel for us.

Bud -- Thank you for the suggestion for looking up passive housing. This is not something I had thought about, and exactly the reason why I headed to a forum to try to get answers. I am a master of campfire cooking, so interior cooking would only really be needed if it is truly foul weather, so something with a simple cooktop , suitable for boiling water, would be sufficient. Any suggestions on styles? Also, Kudos on reminding me about the critters. I wouldn't generally store more than a day's worth of fuel in the shelter itself, since we have an abundant supply in our bonfire stack.
 
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Old 12-06-13, 04:00 AM
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And once this stove is started if you choose wood how do you plan on controlling the temperature?
Plan on also having a back up generator running anyway to run the ref. lighting, water pump?
Already have gas on site?
If it's loss of power how do you plan on keeping the pipes from freezing?
 
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Old 12-06-13, 04:40 AM
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Another area to search would be "off grid cabins". It is a life style that faces many similar problems.

Bud
 
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Old 12-06-13, 11:40 AM
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Again, Bud, that is yielding excellent information. I'm finding a few things I hadn't thought of. Thanks.

Joecaption, the stove would generally only be used for cooking during foul weather, in which case it would generally only be used for boiling water to make a soup, etc, or for extreme cold weather during an emergency. Wood stoves for heating and cooking, as I have discovered, are designed to store heat, so a little fire in the morning would carry heat throughout most of the day until the evening. Better weather would have cooking outside the shelter. If you have suggestions on how to better control the temperature, I would love to hear about it.

Also, our other power source is intended to be solar power, which is actually on a separate thread. We are not planning on having gas at all. The reasons for this is that we have both experienced prolonged outages that saw the nonavailability of any gas forms, from natural/propane to gasoline. We would like to be as self-sufficient as possible should we encounter another extended outage.

As far as keeping the pipes from freezing -- I am not sure what you mean. If you are asking about water pipes, this is an earth-bermed shelter, similar to Tolkien's hobbit holes, with an already existing rainwater reclamation system that is gravity fed. We already use this system for water the flower and summer vegetable gardens. We haven't had any problems with pipes freezing yet, and it is currently 18 degrees here today. I don't know what other pipes you would be referring to.
 
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Old 12-06-13, 04:36 PM
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I haven't had much experience with wood stoves, but I know they will not hold their heat all day long from a fire in the morning. You should do a manual j calculation of your structure to determine its heat loss. You will then have a better idea of how many BTU's your heat source needs to be in the winter to keep the place warm.
 
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Old 12-08-13, 11:46 AM
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I have a spread sheet for manual J8ae -- is this the same thing?

ETA: Also, the 3 wood stoves I am considering all have ceramic/masonry "heat reflectors" that advertise holding and slowly releasing heat for up to 6 hours. In the coldest months, it would be cold enough to build another fire by then. I am aware that advertising can often be false, but even if it only redistributes heat for a few hours, that would mean a fire would not have to be burning constantly.
 
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Old 12-08-13, 12:53 PM
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I looked back quickly but didn't see it mentioned as to how large this shelter is. I suspect it is not huge and being mostly covered in earth it will not take a lot to heat. There would be heat loss to the colder surrounding earth, but that will actually hold a lot of the heat.

As an experiment I used my soccer size rock and placed it next to a hot air duct. It would heat during the on cycle and remain warm for hours. Building a partial brick surround for your wood stove will provide a lot of thermal mass to help hold the heat. But a small space with limited glass won't take much.

Moisture control and indoor air quality will be big issues and must be addressed during construction. Not related to this question but very important.

Bud
 
 

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