# Does firewood still dry below 32 degrees?



## pro5oh (Oct 1, 2008)

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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## Howard M Emerson (Oct 1, 2008)

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


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## savageactor7 (Oct 1, 2008)

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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## Corey (Oct 1, 2008)

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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## FireWalker (Oct 1, 2008)

Keep it exposed to the sun and it will dry.


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## billb3 (Oct 1, 2008)

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


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## mikeathens (Oct 1, 2008)

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


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## ISeeDeadBTUs (Oct 1, 2008)

But which is better . . .

1) Gaining an extra 2% MC, or

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


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## Corey (Oct 1, 2008)

ISeeDeadBTUs said:
			
		

> But which is better . . .
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> 1) Gaining an extra 2% MC, or
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> 2)Having the 180lb load of wood pre heated to say 50 deg ??



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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## Adios Pantalones (Oct 1, 2008)

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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## ISeeDeadBTUs (Oct 1, 2008)

cozy heat said:
			
		

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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!!


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## myzamboni (Oct 1, 2008)

ISeeDeadBTUs said:
			
		

> But which is better . . .
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> 1) Gaining an extra 2% MC, or
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> 2)Having the 180lb load of wood pre heated to say 50 deg ??



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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## Rockey (Oct 1, 2008)

myzamboni said:
			
		

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


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## Corey (Oct 2, 2008)

Adios Pantalones said:
			
		

> 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.



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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## gyrfalcon (Oct 5, 2008)

Greybeard said:
			
		

> 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



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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## fossil (Oct 5, 2008)

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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## BJ64 (Oct 5, 2008)

Rockey said:
			
		

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That was GREAT!


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## BJ64 (Oct 5, 2008)

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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## gyrfalcon (Oct 5, 2008)

BJ64 said:
			
		

> 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.



Got wind in that deep freeze?


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## iceman (Oct 6, 2008)

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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## Saw-dust (Oct 6, 2008)

gyrfalcon said:
			
		

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Another genius shot down by the obvious!

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


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## fossil (Oct 6, 2008)

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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## gyrfalcon (Oct 6, 2008)

fossil said:
			
		

> 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



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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## VTSR5 (Oct 28, 2008)

gyrfalcon said:
			
		

> ...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...



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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## gyrfalcon (Oct 28, 2008)

VTZJ said:
			
		

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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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## glacialhills (Oct 28, 2008)

How do you think your meat gets freezer burned? its the dry freezer air sucking the moisture out of it. want to stop freezer burn? freeze meat in a bag of water so it is surrounded by ice. or vacuum pack...no air circulation no burn. I would think wood  put in there would do the same. I have always thought that winter is when most seasoning occurs in the wood pile. Heck summer is so humid around here I just dont think it wicks moisture out of wood much when the rh is in the 70's.


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## mulkick (Oct 28, 2008)

I've wondered about wood seasoning in the winter also.
We all know h2o expands when frozen.
In northern IL, we get freeze, thaw cycles all winter long.
I'm guessing the expanding, contracting, would help move the water out of the wood, as would the fact that the water has larger "escape" routes.
Think this helps in the winter seasoning process?


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## chiefburritt (Oct 29, 2008)

My father in law, all of 82, would cut his sap boiling wood now through Dec. and use it in the spring. Very low moisture content, it would burn hot and fast as required for wood fired sap pans.  Cut into 32" lengths, split and stacked on the pond bank with exposure to wind and occasional winter sun would dry it out just fine  Once again 82 years of experience.   Now with that being said if you you cut today don't expect to burn tomorrow, that's left to the politicians:>)


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## DavidV (Oct 29, 2008)

Hes but much slower.    my wife dries clothes outside.  even below 32 degrees she will sometimes put towels on the porch (Covered and screened) on a rack....they freze hard but the wind pulls the water off of them and by the next day they are dry.  Cold as hell but dry.  We also dry on rackis in the living room in the evening.  The air inside is usallly so dry in the winter that the moisture is welcome.  Your wood will continue to seasopn...but again....much slower.


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## webbie (Oct 29, 2008)

Wild guess - wood creates some internal heat when it is seasoning and there is some critical mass in the pile (heat storage), so it would take a colder temp than 32 to make it stop drying....

how's that for a guess?


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## chiefburritt (Oct 29, 2008)

Like a January 20 below????


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## savageactor7 (Oct 29, 2008)

Well if you can get chapped hands and lips at 20 below I'm thinking split wood is drying out too.


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## bayshorecs (Oct 29, 2008)

Maybe some of you haven't been outside for an extended period of time on a below zero, very windy day in January.  That was the worst wind burn of my life.  Worse than any sun burn I have ever had.  It felt like 100% of the moisture was pulled out of my face.  It actually hurt to open my mouth!

The wood will still dry out in the winter...


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## chiefburritt (Oct 29, 2008)

In the coldest of winters days there is very little relative humidity!!   Even if there is a lot of snow.  Now out west they all know what a low Rh means in the summertime..  Wildfires.


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## shakermountain (Jan 15, 2011)

Hi all, I'm a new member to hearth here. Originally from northern VT, Now Southern NH.
My wood-burning background began in the energy crisis/oil embargo of 1971: My father, who was a Mechanical and Electrical Engineer and MIT Mathematician (this accounts at least in part for my inherited OCD and deep respect for the scientific method of observation) bought what was to end up being my first saw, a Stihl 024 Good saw when the fuel line wasn't cracked, which happened a lot.

Since then, I've heated partly (or exclusively) with wood over the years, first using the open fireplaces in our 1950's house (one with a "heatilator");then a Jotul mini; Hearthstone II; Hearthstone Heritage; Quadrafire mid-size, and currently a Vemont Castings Montpelier fireplace insert. 

Saws were the 024, then a Wood Boss, and now a Dolmar 510. I like this new saw a lot. Starts right up and seems to want to keep cutting wood even after I shut it down.

After learning the hard way about burning unseasoned, wet wood from our family wood lot, and after I saw one of these used in my first job at Woodbury's bowl mill in Shelburne, VT, I bought a kiln-quality Delmhorst analog moisture meter with the long probe. This is a very accurate meter.  Since the 80's I have routinely checked "control pieces" in my stacks throughout the summer and winter, both to see how they're drying, and to know the best area of the huge stacks had I felled and cut up I should next pull wood from to bring in the house. I always covered the wood enough to keep the center of the pile/stacks dry, but exposed the edges to sun, wind (and wind-driven rain/ snow). I kept some simple notes on the results.


With all that introduction stuff behind us now, and having read all the other posts in this thread, I have two observations to share here:

1) Covered, but with sides wind/sun exposed (shed roof or loose tarp, didn't seem to matter) stove-length wood drys out at a pretty regular rate, pretty evenly throughout each individual control piece, all year round (around a percent or two a month). It will reach an ambient MC of around 9 to 10 % outdoors. After six months and below a 14% MC tipping point, it will burn more readily than it will "sulk and char" (good imagery from an above post here:~)  Splitting increases the drying RATE by a half to a full percentage point or so per month, but it does not affect the MC bottom line, presumably because it allows humidity to infiltrate as easily as collected moisture to evaporate from the wood. Bringing wood dried this way indoors and left for ahwile will allow it to then  dry to about 7%, at which point it it will burn like old 2x4's.
I recommend against bringing non-stack-dried wood into a garage or house as it severely retards drying to be in unventilated space - no matter how hot it gets in summer - and there's the nasty parasite  and carpenter ant potential to think about. I never tested the drying time the one year I did this, but the wood hissed and spat all that winter, and we had to call an exterminator in January.

2) With regards to some of the math in previous posts,  My dad always said: "The more equations one adds to an earnest but theoretical formula, the more critical variables one will have missed in the ultimate field result."


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## wood-fan-atic (Jan 15, 2011)

5cordayear said:
			
		

> Hi all, a new member to hearth here who's heated with wood variously using an open fireplace with "heatilator" Jotul mini, Heathstone II, Hearthstone Heritage, Quadrafire (?) and now a VC Montpelier insert in my various homes in VT and NH since the 1960's.
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> I'm one of those guys whose owned a kiln-quality Delmhorst moisture meter since the 80's and since then have routinely checked my stacks throughout the winter, both to see how they're drying, and to know which area I should next pull from to bring in the house.
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......uh.....what...?? ;-)


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## cptoneleg (Jan 15, 2011)

My opinion is yes, seasonig wood , needs all the seasons, I have noticed that after a hard freeze, ther is more checking, (cracking) of the splits, which stimulates more circulatin.  But you know what they say about opinions, (everyon has one)


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## smokinj (Jan 15, 2011)

Webmaster said:
			
		

> Wild guess - wood creates some internal heat when it is seasoning and there is some critical mass in the pile (heat storage), so it would take a colder temp than 32 to make it stop drying....
> 
> how's that for a guess?



Pretty Good and probably not a guess at all! lol


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## oldspark (Jan 15, 2011)

Not worth a crap compared to the warmer months, think about it and do some research, much more moisture lost with the warmer temps.


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## Wallyworld (Jan 15, 2011)

In the warmer months isn't the humidity higher than when its 20 below. If you have a moisture content higher than the surrounding area its going to give it up.


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## LLigetfa (Jan 15, 2011)

Saw-dust said:
			
		

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That's not the only flaw in that test.  Nature dehumidifies air by varying the temperature.  In the Summer you see this as dew condensed on the grass.  In Winter, you see it as frost on the windshield and hoar frost on trees.

The freezer maintains a relatively constant temperature deliberately so as not to freeze dry its contents.  Yes, there are defrost mechanisms in place but the overall intent is to not dry out the food.

As for humidity Summer or Winter, it is of course relative to temperature and how much of this humidity gets squeezed out of the air will vary by region and the source of the humidity.  Around here, Summer humidity tends to be more constant while Winter humidity fluctuates a lot.

Sometimes I process my wood in Winter/Spring and leave it out all Summer.  In late Fall, I rank it up in my shed tight to the rafters and can see how much the stacks shrink over the course of the Winter by the space that forms under the rafters.

Years ago, before I got educated on the value of staying years ahead and proper stacking, I would leave my processed wood in heaps all Summer and then rank them up in the shed come Fall.  Since heaping doesn't dry evenly, as I was ranking it up, I would sort the wood into now, later, and much later stacks.  As the Winter progressed, the later stacks would become suitable to burn and by Spring, so too would the much later stacks, evidence that wood does in fact continue to dry in Winter.  Also, since I would stack  over 9 feet high in the shed, the much later stack would dry and shrink much more on the exposed face causing the stack to curve and lean, clear evidence of shrinkage.

Since I am so much smarter now, I rank my wood up outdoors right away and stay years ahead so none of this matters any more.


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## iceman (Jan 15, 2011)

This topic has been debated to the fullest...
However, yes would will dry in the winter but less than a warm breezy summer. Warm air can carry much more moisture than cold.o
Snow evaporates at about a tenth(may be 100th gotta look) of an inch a day below 32 
In Jan when the suns rays aren't strong.. 
Think of it this way ... lol if I freeze meat when it thaws its moist like before it was frozen .. maybe not as much but it is 
When you cook the meat (overcooking) it comes out dry.. no matter what temp - higher temps - less time .. lower temps more time..
I believe that the cold does help and contribute ... but I believe wind may be the most important..
There is a thread around here somewhere,  where someone stacked wood in a garage with a fan and got remarkable results.


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## LLigetfa (Jan 15, 2011)

The title of this topic is "Does firewood still dry below 32 degrees?" so why does everyone want to turn this into a debate about whether Summer or Winter is the best drying time?


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## jimbom (Jan 15, 2011)

I got my stove in 2008 and really knew nothing factual about burning wood.  So I developed the habit of marking a split with a permanent marker including the date cut, and the weight when fresh cut and immediately split.  Doing that, I started to get a little idea what my wood was doing in the summer and in the winter.  I still am not very knowledgeable, but am picking up certain information as I go.  Your wood, your climate, your storage location/conditions, your lengths, your split sizes, etc will vary so much from others that you may have to become the expert at your house.  I am finding out my oak is darn hard to dry.


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## oldspark (Jan 15, 2011)

LLigetfa said:
			
		

> The title of this topic is "Does firewood still dry below 32 degrees?" so why does everyone want to turn this into a debate about whether Summer or Winter is the best drying time?


 Well one can think how much it drys in the winter would be of interest to some.


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## LLigetfa (Jan 15, 2011)

oldspark said:
			
		

> Well one can think how much it drys in the winter would be of interest to some.


Keeping it true to the OP...


			
				Greybeard said:
			
		

> 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


How much more it will dry outside of course depends on local conditions, how it is ranked, etc.
What "putting it in storage" means is also subject to interpretation.
Addressing the assumption as well depends on local conditions and the first above.

So, with these details it really is a "how long is a piece of string" question.  Greybeard has not returned to to add any clarity so this thread runs on conjecture and local anecdotes.  At times I think some folks drop these vague "trolling" posts only to sit back and be entertained by the zeal of the respondents.


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## oldspark (Jan 15, 2011)

Well I think it was relevent so I will post as such, since when have a lot of these posts stayed on point all the time.


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## gyrfalcon (Jan 15, 2011)

LLigetfa said:
			
		

> At times I think some folks drop these vague "trolling" posts only to sit back and be entertained by the zeal of the respondents.



I love this.  (not) Here and on every other forum I've ever participated in, there are always some people who join up, ask a complicated question or plead for advice, half a dozen folks leap to help, spend time explaining whatever it is and what to do about it, ask a few questions about the poster's situation-- and the person who asked never shows up again, even take the 20 seconds to post a thank-you.

At least here at Hearth.com, at least the regular denizens manage to make an entertaining argument or two out of it and the OP is quickly forgotten.


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## iceman (Jan 15, 2011)

gyrfalcon said:
			
		

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Did you forget about me?  Already? Cmon  Lol 
We answered this in another long post that brought some real scientific facts 


But the answer is to the person who brought this thread back to life is yes.. but not as much as it would in a normal summer


I


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## gyrfalcon (Jan 15, 2011)

iceman said:
			
		

> Did you forget about me?  Already? Cmon  Lol
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You are unforgettable, Iceman.  (But you weren't the OP in this thread, so I'm not sure why yer askin'.)


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## iceman (Jan 15, 2011)

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Lmao I thought this was the one I started last year!
Wow early onset of what is that memory loss called?


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## LLigetfa (Jan 15, 2011)

iceman said:
			
		

> Wow early onset of what is that memory loss called?


LOL... IKWYM It's right there on the tip of my tongue.


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## mesuno (Jan 17, 2011)

For people who are doubting drying below freezing - that is exactly how instant "freeze dried" coffee is made, albeit under carefully controlled and engineered conditions.

What matters is the relative moisture content of the air - provided it is below 100% it still has potential to remove moisture from wood.

Some other factors are worth mentioning - water in wood is stored in two ways, as "free" moisture such as sap and "bound" moisture trapped as part of the structure of cell walls. Ice swells as it forms, potentially rupturing cell structures and freeing more moisture so it is quite possible that a good hard freeze will overall speed up drying.

Also, below freezing temperatures it tends to snow rather than rain. Snow blows off without wetting the wood so firewood can continue to dry even in a snow storm - not possible when it is raining however.

Mike


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## oldspark (Jan 17, 2011)

Mesuno said:
			
		

> For people who are doubting drying below freezing - that is exactly how instant "freeze dried" coffee is made, albeit under carefully controlled and engineered conditions.
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 So you have a vacuum chamber to put your wood in?


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## mesuno (Jan 17, 2011)

Sadly not 

But the vacuum isn't essential to the process, it just speeds it up. The question was whether or not drying happens at sub zero temps.

Interestingly, you should be able to get "0%" moisture content wood by freeze drying - I wonder how well it would burn :D


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## shakermountain (Jan 17, 2011)

Felled a 12" caliper Shagbark Hickory ten days ago cut it up and stacked it in the shade, covered top, not sides. MC 22%

It has not gone above freezing here since then and we have had a major coastal snowstorm.

Today, all the stove- length log ends are visibly checked. MC now 20%

Read my previous post. Properly stacked and covered firewood dries in winter. No vacuum chamber required. Tired of the naysayers and instigators, I am done with this thread.


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## oldspark (Jan 17, 2011)

I could be wrong but the vacuum process is very important in freeze drying, I dont get it everything dries quicker with heat so why do people seem to think fire wood dries well when it is cold, been burning for over 30 years and have never thought the wood dries very much in the winter.


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## PapaDave (Jan 17, 2011)

iceman said:
			
		

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Sometimers.


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## Mrs. Krabappel (Jan 18, 2011)

PapaDave said:
			
		

> Sometimers.


  LOL!

I hang laundry outside all year, so yup.  Sometimes it gets a little crunchy first.   Sometimes it dries better in February than it does in August.


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## Kilks (Jan 18, 2011)

Fun thread and I love all of the science!  I am a science dork at heart so I had to crank a few numbers and it turns out that ice in air that is 0C or below will always sublimate.  For ice to sublimate it has to have a temperature and pressure below the triple point of 0 C and 0.006037 atm (approximately...).  Even under the worst case scenario of 0C and 100% relative humidity, each cubic meter of air has 4.8g of water.  Convert that to moles and use the ideal gas law (of course assuming water is an ideal gas and under these conditions it would behave pretty much like an ideal gas) and you find that gives a partial pressure of 0.00597atm.  Under these conditions water will sublimate.  If you drop the temperature to say -25C and 10% relative humidity, each cubic meter of air would have 0.1g of water giving a partial pressure of 0.000113atm, far below the necessary triple point.  It is difficult to calculate the exact rate of sublimation due to the large numbers of variables involved, but the conditions are right in terms of pressure and temperature.  Studies that have looked closely at the evaporation rate of snow have found wind (flow rate) to be the greatest contributing factor, and found the greatest rates of sublimation closer to 0 C.  At -5C they were able to measure snow sublimation rates of 0.35E-6kg/s at 8SLPM flow rate, which would translate to a loss of about 1/2 pound of water sublimated in a week in a windy location.
I found it pretty interesting that ice will always want to sublimate when it is below 0C out, even at 100% relative humidity.  That surprised me for sure!  I teach chemistry, so next time we go over phase diagrams I will definitely have another cool example for my students - well at least I will think it is cool  :cheese:


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## BrotherBart (Jan 18, 2011)

OK. So a cord of ice will season if it is cold and windy enough. Right?


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## gyrfalcon (Jan 18, 2011)

Kilks said:
			
		

> Fun thread and I love all of the science!  I am a science dork at heart so I had to crank a few numbers and it turns out that ice in air that is 0C or below will always sublimate.  For ice to sublimate it has to have a temperature and pressure below the triple point of 0 C and 0.006037 atm (approximately...).  Even under the worst case scenario of 0C and 100% relative humidity, each cubic meter of air has 4.8g of water.  Convert that to moles and use the ideal gas law (of course assuming water is an ideal gas and under these conditions it would behave pretty much like an ideal gas) and you find that gives a partial pressure of 0.00597atm.  Under these conditions water will sublimate.  If you drop the temperature to say -25C and 10% relative humidity, each cubic meter of air would have 0.1g of water giving a partial pressure of 0.000113atm, far below the necessary triple point.  It is difficult to calculate the exact rate of sublimation due to the large numbers of variables involved, but the conditions are right in terms of pressure and temperature.  Studies that have looked closely at the evaporation rate of snow have found wind (flow rate) to be the greatest contributing factor, and found the greatest rates of sublimation closer to 0 C.  At -5C they were able to measure snow sublimation rates of 0.35E-6kg/s at 8SLPM flow rate, which would translate to a loss of about 1/2 pound of water sublimated in a week in a windy location.
> I found it pretty interesting that ice will always want to sublimate when it is below 0C out, even at 100% relative humidity.  That surprised me for sure!  I teach chemistry, so next time we go over phase diagrams I will definitely have another cool example for my students - well at least I will think it is cool  :cheese:



Something missing here, I think.  "a loss of about 1/2 pound of water sublimated in a week in a windy location" out of how much what?

Those of us who live in windy northern areas know wood seasons surprisingly fast in the mid-winter months, but our more southerly brethren don't believe us.   Thanks for speaking up.


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## Kilks (Jan 18, 2011)

BrotherBart said:
			
		

> OK. So a cord of ice will season if it is cold and windy enough. Right?


Just make sure it is completely seasoned (sublimated) before you put it in the stove


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## Kilks (Jan 18, 2011)

gyrfalcon said:
			
		

> Something missing here, I think.  "a loss of about 1/2 pound of water sublimated in a week in a windy location" out of how much what?


For the sample in this study they used a cylinder 7cm diameter 1cm thickness - they calculated the rate in kg/s but I just extended it out to pounds per week to get a better sense of the numbers.  Greater surface area of a sample also yields greater sublimation rates, just like evaporation rates.
Yeah, hard to beat a windy winter day for seasoning in my book.


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## Mrs. Krabappel (Jan 18, 2011)

BrotherBart said:
			
		

> OK. So a cord of ice will season if it is cold and windy enough. Right?



:lol: all this tedious science speak is giving me a head-ache.


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## rphurley (Jan 18, 2011)

5cordayear said:
			
		

> Felled a 12" caliper Shagbark Hickory ten days ago cut it up and stacked it in the shade, covered top, not sides. MC 22%
> 
> It has not gone above freezing here since then and we have had a major coastal snowstorm.
> 
> ...


I found a huge Shagbark had fallen in June, 2009. Within a couple of months I had it split and stacked in a single row.  I didn't think I would burn it until next winter.  It's proximity to the house led me to to burn some of it this season, and sure enough, it is as dry as a bone.  If this was White Oak I never would have tried to burn it.


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## bboulier (Jan 18, 2011)

cozy heat said:
			
		

> ISeeDeadBTUs said:
> 
> 
> 
> ...



That's why I belong to this forum.


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## gyrfalcon (Jan 18, 2011)

Kilks said:
			
		

> gyrfalcon said:
> 
> 
> 
> ...



OK, thanks very much.  Very much appreciate that you did your calculations-- and also uncovered the bit about the sublimation happening at below freezing.  That's really interesting, and surprising to us non-geekish types. ;-)


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## OhioBurner© (Jan 18, 2011)

I havent read through this thread but something I noticed made me think of it. My basement is the dryest it has been since installing a dehumidifier. It is saying 50% right now, if that is accurate. Its about 50 degrees. I spilled a container of water and noticed it beaded on the small peice of carpet I had there. Its been almost 2 weeks and the water is still beaded. I think having wind makes a huge difference as even in ~50 degree temps with 50% RH tiny water droplets arent going anywhere, but outside even in colder temps I am sure they wouldnt last a few hours.


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## gyrfalcon (Jan 18, 2011)

â–ºâ–ºOhioBurnerâ—„â—„â„¢ said:
			
		

> I havent read through this thread but something I noticed made me think of it. My basement is the dryest it has been since installing a dehumidifier. It is saying 50% right now, if that is accurate. Its about 50 degrees. I spilled a container of water and noticed it beaded on the small peice of carpet I had there. Its been almost 2 weeks and the water is still beaded. I think having wind makes a huge difference as even in ~50 degree temps with 50% RH tiny water droplets arent going anywhere, but outside even in colder temps I am sure they wouldnt last a few hours.



My totally unscientific observation is that wind is at least, if not more, critical to drying wood than heat per se-- especially humid heat.  Outdoors in winter (serious winter like we have in the north), I'm thinking from what the poster above says, sun matters not at all.

My first winter burning, I ended up doing the usual thing and buying a nice load of good rock maple in late fall that was ostensibly "seasoned" but was really unburnable, and I stacked it up against the north wall of my barn in complete shade.  I lucked into some very burnable firewood, but it only got me through the worst of winter, and by early spring I was flat out unless I started looking seriously at the furniture.  I went over and eyed the wood stacked against my barn, hefted a couple pieces and decided to try it.  Burned like a beaut.

Apparently, I have ideal winter drying conditions-- well below freezing all but a day here and there during four months of winter, low humidity (except when it snows) and nearly constant wind.  Seems only fair, no?


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## gyrfalcon (Jan 18, 2011)

oldspark said:
			
		

> I could be wrong but the vacuum process is very important in freeze drying, I dont get it everything dries quicker with heat so why do people seem to think fire wood dries well when it is cold, been burning for over 30 years and have never thought the wood dries very much in the winter.



Dunno Oldspark.  I don't imagine you have high winter humidity there in Iowa, do you?  Are you below freezing most of the winter?  Try sometime marking a split from your stacks and weighing it on a scale in the fall, then weigh it again in March or April and see what you think.  No question, none, that wood dries significantly over the winter where I am, so much so that I'm not yet convinced it doesn't dry faster than it does in summer.  What it does in the stove is the bottom line, though.


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## oldspark (Jan 18, 2011)

Things dry better with heat even with high humidity, not sure why people think firewwod is any different than anything else, the wood checks much much more in the summer than in the winter. 
Below freezing in winter up here, yes we are in North West Iowa so below zero a fair amount.
Not being a smart ass but the thought of wood drying more in the winter than summer is amusing to me.


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## oldspark (Jan 18, 2011)

Not sure if this is any help to any one but it makes sense to me.
"Snow and ice sublimate, although more slowly, below the melting point temperature. This allows wet cloth to be hung outdoors in freezing weather and retrieved later in a dry state. In freeze-drying the material to be dehydrated is frozen and its water is allowed to sublimate under reduced pressure or vacuum. "


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## cptoneleg (Jan 18, 2011)

Doe's firewood still dry at 32 deg. or below?  

                   !. True
                   2. False

                   Ah;  True


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## Adios Pantalones (Jan 18, 2011)

Ice sublimates.  It happens much slower than water evaporating.  Both happen slower the colder it is.

This is fact.  


Further- when ice sublimates from the outer layer of wood, redistribution (getting the water in the middle to move out to the edge so that it can sublimate) is verry sloow, so you can't just look at ice sublimating and guess how fast wood will dry.  Not even in the same ballpark.  Not in the same league.  Not the same sport.

Phase diagram is a good starting point, but it doesn't address the kinetics (rate) of the problem, which are the question here.


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## cptoneleg (Jan 18, 2011)

Adios, was that a true or false??


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## Adios Pantalones (Jan 18, 2011)

Fruese.  I mean- Talse.

I mean- it dries in the cold, but it is way slower than when it's above freezing.


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## cptoneleg (Jan 18, 2011)

Adios Pantalones said:
			
		

> Fruese.  I mean- Talse.
> 
> I mean- it dries in the cold, but it is way slower than when it's above freezing.



  Thats what I thought you said-voted Thanks


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## oldspark (Jan 18, 2011)

does not amount to a hill of beans in my book.


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## JoeyD (Jan 19, 2011)

I believe some drying happens below freezing but, try hanging some cloths out to dry when the temps stay in the 20's. I'm guessing it might take days to accomplish what you get at above freezing temperature's if they complety dry at all.


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## cptoneleg (Jan 19, 2011)

Everyone agrees;  just afew days before this was posted, I was out in woods where I had some fresh stacks and after a hard freeze it had apeared to be cracking on the ends from maybe a hard freeze, I just thought takes all seasons to fully season wood 1 yr. or more but the winter probably doesn't amount to a hill of beans.  U ever noticwe how some of the meaningless threads get the most response.


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## Mrs. Krabappel (Jan 19, 2011)

JoeyD said:
			
		

> I believe some drying happens below freezing but, try hanging some cloths out to dry when the temps stay in the 20's. I'm guessing it might take days to accomplish what you get at above freezing temperature's if they complety dry at all.



It takes 2 days.


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## moosetrek (Jan 19, 2011)

~*~Kathleen~*~ said:
			
		

> JoeyD said:
> 
> 
> 
> ...



Unless you live out here on the plains, in which case drying takes five days.  Only one to dry (due to the low humidity), and four more to find them after the wind blows them to Nebraska.


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