Does firewood still dry below 32 degrees?

Post in 'The Wood Shed' started by pro5oh, Oct 1, 2008.

  1. pro5oh

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    Just wondering if I have anything to gain by keeping the wood outside through Dec before putting it in storage. I'm assuming under 32 degrees wood doesnt dry much. HELP
     
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  2. Howard M Emerson

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    Grey,
    If the shrinking ice cubes I notice in my freezer are any indication, it may well be that moisture does leave to some extent. I'm not positive, but that's my hunch.

    HE
     
  3. savageactor7

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    Yes I was convinced by the experts here that wood will season in the winter...

    ...chapped hands and lips are the result of the dryness of winter weather. Our wood is outside and covered...of course we have a couple of cords salted away in the woodshed in case of a blizzard but for regular use we draw on our outside wood.
     
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  4. Corey

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    I think it would depend on what 'storage' is. The wood may dry some below freezing (probably through the same processes responsible for freezer burn and/or freeze drying) - but I think that amount of drying, in relation to actual 'seasoning' which takes place during a good, hot summer day, is going to be very small. So storing the wood outside in a pile versus outside in a wood shed probably won't make too much difference. Outside versus in a somewhat heated space - (ie basement, garage, etc) - you might be slightly ahead to put it in the heated space which would mean lower relative humidity in the air and hopefully above freezing, so the water is a liquid.

    Either way, it's getting pretty late in the year to think about drying wood for this burning season. Wood drying now for next season would probably be seasoned regardless of the location.
     
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  5. FireWalker

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    Keep it exposed to the sun and it will dry.
     
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  6. billb3

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    Dry air will remove moisture even from ice.
    Wind will increase this ability.
     
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  7. mikeathens

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    If we're talking 32 celcius, hell yes it will.
     
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  8. ISeeDeadBTUs

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    But which is better . . .

    1) Gaining an extra 2% MC, or

    2)Having the 180lb load of wood pre heated to say 50 deg ??
     
  9. Corey

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    Well, lets see...mathematically (and making a few assumptions:) [ wow, it's a slow day to work through this!]

    180 lbs of wood, 2% moisture = 180 lbs wood x 0.02 = 3.6 pounds of water

    Heat required to vaporize 3.6 lbs of frozen water =

    Ice @ 32F to water @ 32F = 144 btu/lb x 3.6lb = 518 btu
    Water @32F to water @ 212 F = 1 btu/lb per degree = 1 x 3.6 x 180 = 648 btu
    Water @ 212F to steam @ 212F = 540 btu/lb x 3.6 lb = 1944 btu

    So, assuming you had 180 lbs of frozen wood @ 15% MC, you'd expect about 7600 btu/lb or 180 x 7600 = 1.368 million btu. (call it 1.4 million btu for a round number) If that wood had 17% MC at the same starting temp, you'd expect (518 + 648 + 1944) = 3100 btu to be used simply vaporizing the additional water. You'd only get ~ 1.396 million btu out.

    ie - the wet wood cost you 3100 btu

    For cold wood, It looks like most hardwoods have a specific heat of ~ .287 btu/lb-F, so to raise 180 lbs of wood from 32F to 50F would take 180 x (50F-32F) x .287 = 1446 btu

    so warming the wood saved 1446 btu

    Overall, on these specific conditions, you'd be better off with dry wood versus warm wood. Though you also have to consider where the warmth for the wood came from in the first place...if it happened to be solar or some other external source, then this is truly a gain. If the heat came from simply being in the same room from the stove - then you've only moved heat from the room into the wood...you haven't really gained anything.
     
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  10. Adios Pantalones

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    It's more than that. Water is known to decrease the efficiency of the burn- as in- smoke and soot. That means that some heat is lost because it is never combusted and just goes into particles and creosote.
     
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  11. ISeeDeadBTUs

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    Now THAT is some good sheetz!! But the hydronic is in a detached building, so the heat lost off the skin of the unit is lost anyway. Now it goes into the wood. Plus it lowers the MC a bit too.

    Reminds me of the magnets they said to put on your fuel line back in the 70's. If you combine all these savings, you eventually become so efficient you have to take wood OUT of the boiler every so many hours!!
     
  12. myzamboni

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    If it's not this years wood, who cares. Oh that's right, I forgot you have an OWB and probably don't season. ;-P
     
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  13. Rockey

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    No need to season a Goodyear or Firestone. They produce the best smoke before dry rotting.
     
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  14. Corey

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    It could be - I was kind of working under the main assumption that the main efficiency loss would be from 'drying' the wood in the firebox, then the wood will combust normally after that. But I suppose if the act of drying one piece killed off the secondary burn that you could have had from other wood in the firebox, then the efficiency loss could compound.

    So, yes - as we say all along...the wood has to be dry!
     
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  15. gyrfalcon

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    I can tell you from experience that splits, at least, definitely continue to dry in cold weather. My personal opinion, though I obviously haven't done any scientific experiments, is that air is at least as, if not more important, than heat.

    Last year being my first year burning, I got the typical beginner's load of wood that was supposedly "seasoned" but turned out not to be and charred and sulked in the firebox rather than burning. This particular batch then spent the winter stacked loosly against the north wall of my barn-- ie, virtually no sun, but exposed to wind, snow, etc. By early spring, when it was still cold and I was running out of my supply of seasoned wood, I started eyeing the pile next to the barn and discovered that the pieces with the greatest exposure were well cracked on the ends and substantially lighter than they had been when I had stacked them at the beginning of winter. They turned out to burn pretty well.

    I'm not claiming the wood got totally seasoned in 4 winter months outside, it didn't, but it clearly had progressed significantly during that time.

    So I'd say, all other things being equal, if you need to squeeze every bit of seasoning you can out of your situation, yes, it will help to leave it outside as long as you can. Obviously, it will help if you can stack it so it's very loose and as exposed on all sides to as much air and sun as you can manage. You might want to be ready with a few tarps to throw on it if snowfall threatens before you get it moved inside, but by all means take the tarps off as soon as the snow stops.
     
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  16. fossil

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    You most definitely do not need to get frozen water up to melting and then up to boiling to convert it to vapor. Just google "sublimation", and you can learn about water's ability to change phase from solid to vapor without passing through the liquid phase. Anybody who lives where it stays really cold for a long time has observed this phenomenon...snow piled up begins to "go away" even when the temps stay below freezing. Yes, wood will continue to dry, but probably not nearly so quickly as during higher temperature weather. If the water in the wood is frozen, then the sublimation is likely to take place only very close to the exposed surfaces. Splits are better than rounds. Small splits are better than large splits. Surface area of exposed wood (not bark) is key. Rick
     
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  17. BJ64

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    That was GREAT!
     
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  18. BJ64

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    I'll have to pull some splits from the pile. Check the H2O and put them in the big deep freeze in the shop and check them again in a month.
     
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  19. gyrfalcon

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    Got wind in that deep freeze?
     
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  20. iceman

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    yes and no
    do we think think wood swasons better in summer ..prolly
    will it continue in winter yes
    but it location location
    we had so much rain this summer which equalled less sun and more muggy days= less seasoning time
    sept was dry low rh and sunny = better seasoning time
    so i expect to get more from sept thru dec than what i got from may thru aug!
    only time will tell!
     
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  21. Saw-dust

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    Another genius shot down by the obvious!

    (don't worry...I know that cowboy from another forum.)
     
  22. fossil

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    Freezers are ventilated...that (plus some other clever uses of localized intermittent heating & things) is how they make them "frost-free". Without ventilation, the vapor produced through sublimation just keeps re-freezing on all the cold surfaces. Remember mom or grandma having to "defrost" the freezer compartment of her refrigerator? Any modern freezer has ventilation incorporated into it. Rick
     
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  23. gyrfalcon

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    Yah, but I bet none of 'em get above, oh, say 5 or 10 mph. ;-)

    It would be an interesting experiment, but it's sure not equivalent to the wood being outside.
     
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  24. VTZJ

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    Charred and sulked? I'll be damned if that doesn't capture it! Very nice turn of phrase. Now let me guess: Underemployed English major?
     
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  25. gyrfalcon

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    Hah! Nope. Underemployed long-time freelance copy editor. Thanks for the props. It sure doesn't take long, though, before you start taking the balky behavior of the firewood personally.
     
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