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Drying wood indoors using a dehumidifyer

Post in 'The Wood Shed' started by MOHAWK1, Sep 26, 2011.

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  1. cptoneleg

    cptoneleg Minister of Fire

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    128 sq.ft of bushes don't buy them they burn really fast

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  2. Battenkiller

    Battenkiller Minister of Fire

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    Only on the outside surface. You want all of the energy from the sunlight to get inside the plastic barrier. As I said, like a greenhouse.
  3. MOHAWK1

    MOHAWK1 New Member

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    Hello everyone and thanks for all the input on this issue, I had originally posted this on monday, that day i split open a piece of red oak that sat in the log form for 2 years and was opened up and stacked this june to test the moisture content. Th meter read 35 percent which is as high as it goes so I thought this wood will never be ready in 4-6 weeks. I had the idea of bringing the wood into the quonsa hut to finish drying, using fans a dehumidifyer and being able to control the temperature. With the ability of being able to control these 3 elements of wood seasoning I thought i would post it on here get some input and give it a try. I brought in 3 wheel barrel loads on the monday turned on 2 fans set the dehumidifyer to 35 and let it sit till today. I split open 9 random pieces and they were all between 22-25 percent mc,
  4. Swedishchef

    Swedishchef Minister of Fire

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    Hey mohawk.

    Glad to hear that it worked! That is good news!

    WHere in Ontario do you live? I am in QC.

    Cheers!

    Andrew

    PS, pics are always nice!
  5. benjamin

    benjamin Minister of Fire

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    ... @ 80 degrees F and 80% humidity. Problem is the wood won't give up water that fast at a high humidity or lower temp. I'm guessing you're better off moving it into the basement a few weeks before you burn it and letting the wood heat do the work for you.
  6. Battenkiller

    Battenkiller Minister of Fire

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    Sounds like you're going ahead with this. Glad to see you got some quick results. If it was me I would bring about a cord inside the hut, then erect a makeshift shelter around it and put the dehumidifier and fans right inside with it. No use dehumidifying the air inside the entire hut when all you want is to get the air in contract with the wood at a lower RH.

    Several pallets could be set up with tarps to enclose it all, making a real cheap but highly effective low-tech kiln. Plus, by enclosing it within a small space, the temperature will go up from the heat produced by the dehumidifier itself. That will further lower the humidity since RH is temperature dependent. This is what the big commercial dehumidification kilns do, and it will speed the process up dramatically.

    FWIW the drying rate will slow down a lot once the wood hits about 20% MC. At that point, you can bring in another cord and moved the pallets and tarps and everything over to that pile and start all over again. In my basement (which I jokingly call the "Battenkiln"), wood dries to completion from green to 20% in about 3 weeks, but that is at a very low humidity (~20-25% RH). In my case, it is the constant infiltration of dry winter air that gets heated up to about 85-90º by the stove in the basement that does the trick. You won't be able to get the RH that low using dehumidifiers, but you should still be able to get a cord dry in 4-5 weeks... maybe sooner, I have no direct experience with artificially drying firewood in any other way but the way that has worked for me for 21 years now. Dehumidification of the air - by whatever means - definitely works, and it works faster than outside in all but the driest outdoor environments.


    Below is the data and chart from last year's controlled experiment. The shape of the curve gives an indication of how slow the drying goes after a while. No use going on after that point, it just will not be cost effective.

    Good luck, and keep posting the results. Then post your electric bill when it is all dry. ;-)

    Attached Files:

  7. Heartwood

    Heartwood New Member

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  8. Heartwood

    Heartwood New Member

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    I had to speed things up a few years ago. Maybe what I did will help your process go even faster.

    Using some logic related to the sciene that Battenkiller shared about surface area, I split my splits. In my simple mind, I was just figuring that a little log will dry faster than a big one. It didn't cut the time in half (bet Battenkiller has some big formula for that), but it did get my moisture down quicker.

    You then have issues with buring smaller, faster splits. But if you're like me, I had other wood to mix in.

    PJ
  9. MOHAWK1

    MOHAWK1 New Member

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    Hello again and thanks for all the comments, to maintain 18-20 MC and not overdrying the wood, what would be the optimum temperature and RH to get the stabilized EMC of 18-20 percent,
  10. Battenkiller

    Battenkiller Minister of Fire

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    If you look back on page 2, post #34, you will see from the chart that an EMC of 18-20% would be maintained at a RH of between 87% and 90%.


    Intriguing, eh? A very good argument against long-term storage of firewood.


    The question then becomes, "How long does it take to get there?"

    I would say that for large splits (6" thick on average, 18-20" long) the wood would need to be seasoned for at least 18-24 months to get there. 4" splits only need about a year, depending on the length they were bucked to. Shorter wood seasons a lot faster.

    After that point, how long would it take to get down to as dry as it can get in your environment? Using conventional wisdom from the air-dried lumber industry, I'd hazard a guess that it would take about one year per inch thickness of the split... minus a fair bit because firewood is a lot shorter than lumber and does a lot of its drying from the ends. So maybe 3-4 years for 6" splits to get down to the EMC found in most of the continent - 12-14% MC.

    Some areas around the Great Lakes, much of Michigan for example, may never see their wood dry below 16-18% MC come burn season no matter how long it is stored. A quick look at their average monthly RH percentages will tell you why.

    Then again, you have to take those combustion efficiency charts i posted with a large grain of salt. There are a lot of variables. Large dense splits of primo hardwood at 14% MC might actually outgas a lot slower than thin pine boards at 18% MC, so the combustion efficiency and overall efficiency would be better with the drier wood. Most experienced burners like big splits or rounds of hickory, locust, beech, hard maple, and black birch that have had long seasoning times. It is really all about knowing your stove, your wood, your draft, etc. Like medicine, woodburning is based on science, but is practiced as an art.
  11. Battenkiller

    Battenkiller Minister of Fire

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    There have been at least a half a dozen rigidly controlled scientific studies over the last 30 years that show conclusively that wood that is too dry will produce more creosote in the chimney than wood that is too wet. These studies have not been well received on this forum, though. :blank:

    Consensus here is that the studies must be flawed because they contradict what folks seem to observe in their experience. Give me a flue that is accurately weighed by scientists before and after each burn session over anybody's anecdotal observations.

    "Too dry" and "too wet" are arbitrary terms anyway. The wood used in these studies wasn't oven-dry on the dry end, nor was it fresh cut on the wet end. I think the "wet" hardwood was semi-seasoned red oak at about 42% MC. Interestingly, that's just about the MC of fresh-cut white ash, and everybody knows you can cut an ash tree down and throw it right in the stove in a pinch. So, it's not like they were using oak fresh off the stump (at over 70% MC).

    That said, there are many ways to safely burn wood that is "too dry" once you really know your equipment. Split size, wood density, draft control, load size, and stove packing are some of the controllable variables that may skew the outcome.

    The most creosote I ever produced in one season was about 15 gallons!!! I did that by using kiln-dried pallet scraps from my buddy's pallet making operation. I was doing everything wrong. Splits too small, not dense wood, choking it down too far to control the fire, etc. Boy, did my sweep ever read me the riot act about that! If I ever had a runaway fire in the stove (easy to achieve with kiln-dried pallet wood) I would have likely gone up in smoke once all that creo ignited. After that experience, I would never again use - nor would I recommend - pallet wood to try to heat with (although it makes awesome kindling)
  12. My Oslo heats my home

    My Oslo heats my home Minister of Fire

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    I still can't understand the logic here. Dark colored roofs create more heat than lighter colored roofs, both the surface and the space beneath them. Dark colored cars also do the same. Even dark colored t-shirts in the sun. I still believe the space underneath a black colored platic topper will create more heat in the space beneath it vs. clear platic will.
  13. Battenkiller

    Battenkiller Minister of Fire

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    Then do it your way. ;-)
  14. maple1

    maple1 Minister of Fire

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    If you go black, the suns rays won't reach past the black. If you go clear, they will get inside and heat everything up inside radiantly and the plastic will trap the heat. The black topper will absorb heat, but not as much heat as everything inside will if the suns hits that - and even then the black will give the heat up both ways, inside and out. Also, I think dark bark on the wood that is piled inside will absorb more heat from direct sunlight hitting it than from air that has been warmed a bit by warm air between it and a hot dark overhead surface.

    A dark shirt is warm in the sun, but your skin will get a lot hotter without a shirt there. Similarily, using the car analogy, I think the air inside the car interior (where there is glass) will be a lot hotter than in the trunk, with all dark steel over it and no glass.

    Or at least that's what the seat of my pants is telling me....
  15. Battenkiller

    Battenkiller Minister of Fire

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    Your pants are very well informed. :coolsmile:
  16. RyanB

    RyanB Member

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    Getting back to the original question about the dehumidifier.... in the fall of 2008 I was forced to do this very thing. We moved to our new location that september and started cutting mostly ash almost right away. We burnt thru the wood we purcashed from the original owners (guy was cheap and wanted every last penny possible) by Christmas. And started burning our amazingly dry, dehumidified wood! Here is what I did. For starters my "hobby shop" is very well insulated and has a brand new at the time, non EPA wood stove rated for 2000 square feet. I stacked 12 face cords in the shop (floor to ceiling, stacked 16" inches appart from each other stack). The next part of the equation before the dehumidification was to get some heat in the shop! I went out and cut down a totally dead stand of poplar with a moisture content of under 20%. I put 6 face cords of the poplar in the shop away from the stacks of ash. I started burning the poplar and landed up keeping a temperature of 35 degree's celcius 24 hours a day with 3 firings every 24 hours. I then had two nice sized box fans pushing the heated air thru the piles. I then fired up my 140 pint dehumidifier with it draining into the floor drain. Starting with 100% green ash, within 3 weeks I had the entire stack down to 25%MC in the middle of splits, 2 week later I had MC down to 15% and was ready to shut it all down and take it into the house. I have yet to have any "seasoned" under normal methods burn as well that 12cord did and if it wasn't so much work to move it all into the shop prior to the house....I would be doing it all again in a heart beat!

    Ryan
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