Wood Heat

Discussion in 'General Homesteading & Building' started by Bigmike7733, Jan 5, 2009.

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  1. Bigmike7733

    Bigmike7733 Guest

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    I'm not shour if this is a good question as there may not be an exact answer but ill let you have it anyway.

    I was wondering if there was a formula for how much btu you would need to heat lets make it easy and say a 10x10 room (with wood) 65 70 degrees i don't know if im asking this question right but i want to heat a little hunting cabin me and my friend just built and also use it as a SHTF shelter if need be, we are trying to estimate how much wood we should have up there to get us threw a winter so how much btu dose a wood stove put out? or how big it needs to be? the cabin is insulated and any other questions i need to answer to narrow it down just let me know.
    Thank you,
    Mike

    P.S. sorry i have the grammar and spelling of a child
     
  2. Canadian

    Canadian Well-Known Member

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    I think there are too many variables to guess. I think you're best off to spend a day at the cabin doing some work on the place and run the stove all day and see what you burn.

    Take the # of logs and divide by the number of hours you were there = logs per hour.

    # logs per hour x 24 = how many logs you need for one day. Then all you need to do is figure out how many days worth you want to keep.

    That should do it.
     

  3. northernontario

    northernontario Well-Known Member

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    Different wood stoves have varying efficiencies. So the heat energy produced from burning one piece of wood in stove A doesn't equal the heat energy produced from stove B.

    You've got some of them listed, but the factors that affect how much wood (energy) is required to heat the cabin would be:

    -insulation value of walls, ceiling, floor, windows - No point heating a space that can't hold it in.

    -how well "sealed" your doors/windows are - air coming in means heat loss.

    -cold/fresh air supply for stove - some cheap stoves draw air from the room for combustion. This leads to a pressure differential in the building. IE... low pressure in the room with the fire place draws air from other rooms, and from airgaps in doors/windows, meaning cold air coming into the house, cooling down areas far away from the stove. A good wood stove or fireplace has the option to plumb in a cold/fresh air line directly from the outdoors. You control where the air comes in... helps prevent cooling areas far from the stove.

    -efficiency of the stove - an expensive stove with a "secondary burn chamber" to help burn all the energy contained in the wood is more efficient than a cheap stove. A better built stove has thicker steel plate, fire bricks, etc... allows the fire to burn hotter, means the stove lasts longer.

    As far as calculating the required BTU's to heat a room... that depends on the heat loss of the room. The requirement for a room with an R20 insulation value is much higher than a room with an R50 insulation value.

    Like "Canadian" says... you can do the trial & error method... run the stove for a day, or a week... calculate how much you used during that time, and work that out into wood required for the season/year. Always over-estimate.
     
  4. Magus

    Magus Scavenger deluxe

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    Sounds kind of like my situation,the room is 14x14 here,it depends a lot on the stove and the kind of wood used,I have burned two wheel barrow loads a day when its cold and wet,I normally use oak for long lasting fires and poplar for fast heat.
     
  5. Woody

    Woody Woodchuck

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    As pointed out lots of information left out, first would be what area or climate are we talking about? You’ll need more wood in northern Vermont than in North Carolina. I’ve lived in both places so know this for a fact. ;)

    With a 10 x 10 room it isn’t going to be 60 to 70 degrees in there… unless you leave a window open, have no insulation or are using a tiny stove. Wood stoves throw off some heat when they get going, it is going to be toasty warm as long as you keep the fire stoked.

    How much use it will get as a hunting camp will dictate how much wood you’ll need. I would say start with at least a full cord and work from there. It might sound like a lot but wait until it gets cold and you make a couple trips to the pile and watch it disappear. You’ll be better able to judge after a winter hunting what it will take for a full years worth. Then make sure you have more than that piled and ready to go. No matter how well you plan there is either way too much or not near enough wood every year. I always over plan and cut more than needed, it can be used for next year. Let me tell you, it really sucks going out in late winter/early spring to cut wood.
     
  6. Bigmike7733

    Bigmike7733 Guest

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    Thank you guys for all the info I think I will go up this weekend and see how much i use. Again i appreciate the help

    thank you
    mike
     
  7. Magus

    Magus Scavenger deluxe

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    Need any help on wood storage and preperation?
    wood types etc?

    I help run a wood lot. :)
     
  8. pubwvj

    pubwvj Tinker, Tailor...

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    There is a complex formula and it is possible to figure out. You need to know about thermal mass, which helps with heat retention when doors open, traffic, insulation, air exchanges, surface area and such. Basically calculate the rate of heat loss. Next comes figuring the BTU value of the wood. This too will be fairly complex and even for the same species can have a bit of variability.

    But, let me simplify and give you my experience:

    Our 14'x20' cottage uses about 1 cord per year of dry maple hardwood in our northern Vermont climate. We like our house a little cooler than some. We have a lot of windows which gives solar gain but loses heat at night. The roof insulation is not complete. I haven't made shutters or curtains yet. But that gives you an approximate idea. That's 252 sq-ft so about twice the square footage you're talking with your 10x10 room.

    All that said, a cold winter vs a warm winter will make a big difference. Another huge factor is wind - try to not have it hitting the cabin as it steals heat.

    My suggestion would be to have three cords of wood on hand. Then the rest is drying until needed next year or the following year but always there if you burn through it faster. Experience will give you real results.

    Here's the cottage if you want to see it:

    Sugar Mountain Farm: One Year Construction Mark

    Cheers,

    -Walter
     
  9. The_Blob

    The_Blob performing monkey

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    In my limited experience, a good rule of thumb is that if it grows fast it will have more water in it. That means higher dry time and lower mbtu/cord when dried. If you burn for heat, then it's a big deal. If it's for ambiance then anything dry is good.

    That is if it smells OK. ;)

    mBTU's/cord charts:

    Sweep's Library - Firewood BTU Comparison Charts
     
  10. Jerseyzuks

    Jerseyzuks Well-Known Member

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    for such a small area, a tiny potbelly stove burning small sticks will probably keep it plenty warm.