Bone dry, but still Sizzle?

[WoodyIsGoody]

I did a quick calculation and, for one pound of oak, the difference between starting at 0F and starting at 70F is equal to about 6 percent of the heat you get from burning it. So it actually makes more of a difference than I expected.

I'd like to see your work because I got a different answer than you by a factor of 8+. And, at only about .7% of the btu value of the wood, my answer seems more intuitively correct. Here's my work:


The amount of energy required to raise the temperature of a substance 1 degree C is called the specific heat. The specific heat of firewood in this example needs two components, that of the wood and that of the water. Since we are measuring the amount of heat required to raise the firewood from 0F (-9C), it’s necessary to separate the two components because one (the H2O) will be going through a phase change (from solid to liquid) while the other (the solid wood) will not. The phase change absorbs a significant amount of energy without a change in temperature so our calculation would not be accurate without including the energy necessary to accomplish the phase change.

The specific heat of a pound of oven dried wood is roughly 1/4 that of a pound of water. If that water starts out as a solid (i.e frozen) it needs to go through one phase change transition, the change from a solid to a liquid. The amount of heat required for the phase change doesn’t involve ANY change of temperature of the water, that must be added on. It's also necessary to add in the energy required to raise the temperature of (dry) wood portion of the load to get a complete answer.

If that doesn’t have your head spinning yet, let’s look at some numbers.

Say your load is 40 lbs. of firewood w/ 15% moisture content and we will calculate how much heat energy it takes to bring that wood up to the same temperature it would be if the wood had been sitting at room temperature for a week.

At 15% moisture, a 40 lb. load contains 6 lbs. of water leaving 34 lbs. of 0% moisture "wood".

Now we’ll convert to metric to make it a whole lot easier.

6lb H20 = 2722g 34 lb. dry wood = 15,422g

First we’ll calculate the amount of energy required to raise just the water portion of the load (in this case a solid at 0F (-18C) up to 70F (21C). It takes 1 calorie to raise 1 gram of water 1 degree C. So, the heat needed to raise the water will be 39 cal/gram because we're raising it 39 degrees Celsius (from -18c to 21c). With 2722g of water, that’s 39 x 2722 calories or 106,158 calories.

To that figure we need to add the heat of fusion required (to convert 32 ice to 32 degree water). The heat of fusion (to go from solid to liquid) of water is 80 cal/g. With 2722g of water, that’s 80 x 2722 calories or 217,760 calories. Adding the temperature rise energy (106,158) to the heat of fusion (217,760) gives the total energy required to warm just the water portion of the wood. Which is 323,918 calories. You might notice that two thirds of the energy on the water side of the equation is consumed simply going from frozen to thawed (without contemplating any actual rise in temperature).

The specific heat of dried wood (0% water) is about .27 cal/gram/degree Celsius. This only varies slightly from specie to specie. This is the energy required to heat the wood without water one degree C. Since we need to raise 15,422g of wood 39 degrees C, it’s 39 x .27 x 15,422 or 162,394 calories. To calculate the energy required for the entire 40 lb. load (water and wood, we simply add the two totals together. 162,394 + 323,918 or 486,312 calories. To convert calories to btu’s we multiply by .004 which gives us 1,945 btu’s.


The accepted btu value for one lb. of wood (any species) at 0% moisture level is 8660 btu’s. Since we know our wood weight without moisture is only 34 lbs., our 40 lb. load of 15% moisture wood has 294,440 btu’s (34 x 8660) Since 1,945 btu’s will be consumed simply warming the wood from 0C-21C, we will be deficient by that amount vs. using wood already thawed and warmed to room temperature. Instead of starting with 294,440 btu’s we’ll be starting with 292,496 btu's or 99.3% of the amount that would have been available had the load been pre-warmed warmed to 21C (70F).

That's only 0.7% difference! In other words, only 0.7% of the total btu value of the wood goes to warming it up to room temperature from 0F.

So if you're looking at overall energy efficiency, I guess the trick is to bring your firewood inside on a warm day!

Good luck finding a winter day so warm that this isn't the small loss that it is (remember, these calculations are based on wood that is frozen solid at 0 degree F!) You would have to bring your entire season's worth of wood inside before it got cold in the fall to avoid this 0.7% heat loss. But you can keep this loss as low as possible by only bringing good, dry wood inside!

 

[FaithfulWoodsman]

Nice work. Without checking your values and conversions, your calculations appear correct. However, even as thorough as you've been there are still variables unaddressed. For one if pressure is constant and the air dry, which it would be, sublimation may occur on a super hot bed of coals. Don't remember specifics, but I do recall that sublimation takes considerably more energy than phasing from solid to liquid, whether provided by the coals or wood, result would still be a larger net loss. Regardless i think we are in danger of getting a little too far into the weeds with this one.
Cause.........

Good luck finding a winter day so warm that this isn't the small loss that it is (remember, these calculations are based on wood that is frozen solid at 0 degree F!) You would have to bring your entire season's worth of wood inside before it got cold in the fall to avoid this 0.7% heat loss.

1. It's been within 15° of 70° for two weeks here, 65° today
And
2. I bring 1/4 cord from the shed outside my basement at a time. It reaches 70° within hours and lasts for 7-12 days depending on the weather.
Love this forum.

 

[WoodyIsGoody]

Nice work. Without checking your values and conversions, your calculations appear correct. However, even as thorough as you've been there are still variables unaddressed. For one if pressure is constant and the air dry, which it would be, sublimation may occur on a super hot bed of coals. Don't remember specifics, but I do recall that sublimation takes considerably more energy than phasing from solid to liquid, whether provided by the coals or wood, result would still be a larger net loss. Regardless i think we are in danger of getting a little too far into the weeds with this one.

I like the way you think!

The heat of sublimation is equal to the heat of fusion (solid to liquid) + heat of 100C temperature change (from 0C-100C) + heat of vaporization. But I didn't count that because we are only going to room temperature with this exercise. However, you're right. My calculations don't take into account the energy of any moisture that evaporates from the wood (regardless if it sublimates or evaporates). If the wood dried through this process, we would no longer have 15% moisture content! So I was trying to do the calculation for the warmed wood assuming a steady 15% moisture content. And even though the amount of energy required to sublimate water is quite high, the amount of water that sublimated (or evaporated) would be very low (assuming we are just bringing the wood to room temperature).

Things get complicated real fast when we try to mathematically model the real world.

 

[Hasufel]

I'd like to see your work because I got a different answer than you by a factor of 8+. And, at only about .7% of the btu value of the wood, my answer seems more intuitively correct. Here's my work:


The amount of energy required to raise the temperature of a substance 1 degree C is called the specific heat. The specific heat of firewood in this example needs two components, that of the wood and that of the water. Since we are measuring the amount of heat required to raise the firewood from 0F (-9C), it’s necessary to separate the two components because one (the H2O) will be going through a phase change (from solid to liquid) while the other (the solid wood) will not. The phase change absorbs a significant amount of energy without a change in temperature so our calculation would not be accurate without including the energy necessary to accomplish the phase change.

The specific heat of a pound of oven dried wood is roughly 1/4 that of a pound of water. If that water starts out as a solid (i.e frozen) it needs to go through one phase change transition, the change from a solid to a liquid. The amount of heat required for the phase change doesn’t involve ANY change of temperature of the water, that must be added on. It's also necessary to add in the energy required to raise the temperature of (dry) wood portion of the load to get a complete answer.

If that doesn’t have your head spinning yet, let’s look at some numbers.

Say your load is 40 lbs. of firewood w/ 15% moisture content and we will calculate how much heat energy it takes to bring that wood up to the same temperature it would be if the wood had been sitting at room temperature for a week.

At 15% moisture, a 40 lb. load contains 6 lbs. of water leaving 34 lbs. of 0% moisture "wood".

Now we’ll convert to metric to make it a whole lot easier.

6lb H20 = 2722g 34 lb. dry wood = 15,422g

First we’ll calculate the amount of energy required to raise just the water portion of the load (in this case a solid at 0F (-18C) up to 70F (21C). It takes 1 calorie to raise 1 gram of water 1 degree C. So, the heat needed to raise the water will be 39 cal/gram because we're raising it 39 degrees Celsius (from -18c to 21c). With 2722g of water, that’s 39 x 2722 calories or 106,158 calories.

To that figure we need to add the heat of fusion required (to convert 32 ice to 32 degree water). The heat of fusion (to go from solid to liquid) of water is 80 cal/g. With 2722g of water, that’s 80 x 2722 calories or 217,760 calories. Adding the temperature rise energy (106,158) to the heat of fusion (217,760) gives the total energy required to warm just the water portion of the wood. Which is 323,918 calories. You might notice that two thirds of the energy on the water side of the equation is consumed simply going from frozen to thawed (without contemplating any actual rise in temperature).

The specific heat of dried wood (0% water) is about .27 cal/gram/degree Celsius. This only varies slightly from specie to specie. This is the energy required to heat the wood without water one degree C. Since we need to raise 15,422g of wood 39 degrees C, it’s 39 x .27 x 15,422 or 162,394 calories. To calculate the energy required for the entire 40 lb. load (water and wood, we simply add the two totals together. 162,394 + 323,918 or 486,312 calories. To convert calories to btu’s we multiply by .004 which gives us 1,945 btu’s.


The accepted btu value for one lb. of wood (any species) at 0% moisture level is 8660 btu’s. Since we know our wood weight without moisture is only 34 lbs., our 40 lb. load of 15% moisture wood has 294,440 btu’s (34 x 8660) Since 1,945 btu’s will be consumed simply warming the wood from 0C-21C, we will be deficient by that amount vs. using wood already thawed and warmed to room temperature. Instead of starting with 294,440 btu’s we’ll be starting with 292,496 btu's or 99.3% of the amount that would have been available had the load been pre-warmed warmed to 21C (70F).

That's only 0.7% difference! In other words, only 0.7% of the total btu value of the wood goes to warming it up to room temperature from 0F.




Good luck finding a winter day so warm that this isn't the small loss that it is (remember, these calculations are based on wood that is frozen solid at 0 degree F!) You would have to bring your entire season's worth of wood inside before it got cold in the fall to avoid this 0.7% heat loss. But you can keep this loss as low as possible by only bringing good, dry wood inside!

I think I figured out the problem--I was the victim of bad data. Also, I calculated for dry oak and ignored water entirely, and I think some of our physical property data might be off as well. Here's how I did the math:

H=mcT [where H = change in enthalpy, m = mass, c (actually c-sub-p) = specific heat, and T = temperature change]

I did this all in English units to keep it simple, so...

H = 1 pound X 5.73 BTU/lb F X 70 F = 401 BTU needed to raise 1 pound of oak by 70 F. The heat capacity value was for oak timber, found at http://www.engineeringtoolbox.com/specific-heat-capacity-d_391.html .

The figure I used for the heat value of oak is 6388 BTU/lb, which is a bit different than the figure you used (source = https://en.wikipedia.org/wiki/Wood_fuel but because I don't blindly trust Wikipedia I calculated a similar figure for oak at http://www.engineeringtoolbox.com/wood-combustion-heat-d_372.html .

So we have 401/6388 = 0.063 or 6.3 %.

HOWEVER, I ran the calculation in metric and came up with an order of magnitude difference...0.63 % rather than 6.3 %. I traced the problem to the heat capacity of oak, which the site I listed above gave as 5.73 BTU/lb F. The same site gave the corresponding value as 0.57 cal/g C but that should calculate out to be almost exactly the same as BTU/lb F, so it appears that the heat capacity value I used was 10 times too large. Using the smaller value, I now get a number much closer to yours.

And now that my brain hurts, it's time to go outside and play with wood!

 

[WoodyIsGoody]

I think I figured out the problem--I was the victim of bad data. Also, I calculated for dry oak and ignored water entirely, and I think some of our physical property data might be off as well.

I agree, the engineering toolbox gives a value for the specific heat of wood that is 10 times higher for the imperial measure vs. the metric. They also give values for different species of wood that vary from .31 cal/g/C (red beech) to .60cal/g/C (pockwood, a tropical hardwood) and yet they fail to state the all important factor, moisture content. I would assume the all the readings between .3 and .38 are for kiln dried wood around 10% moisture or less but that some of the other figures could be culled from different sources and represent wood with higher moisture content. To further complicate matters, the specific heat of dry wood (and most organic materials) increases linearly with temperature, from around .27 cal/g/C at 0C to .37 cal/g/C at 100C.

My calculations used .27 cal/g/C but assumed 0% moisture. If you assume 20% moisture (H2O has specific heat of 1.0) then the .27 cal/g/C that I used for dry wood becomes .38 cal/g/C for 15% moisture wood and .42 cal/g/C for 20% moisture wood.

If I were to calculate this again, I would adjust the heating value of 0% moisture wood from 8860 btu/pound to 7974 btu/pound because I forgot to adjust to account for the fact that stoves are not 100% efficient at extracting the heat. In other words, a lb. of 0% moisture wood has around 7974 btu's useable heat when burned optimally. This number, reduced a further 20% to account for water content, will correspond almost exactly with the number you used for 20% moisture wood. A good explanation of firewood btu values is offered here:

https://chimneysweeponline.com/howoodbtu.htm

In a future discussion we will need to explore the effect of water content on USEABLE heat. This will get into the heat of vaporization and the numbers are quite astounding! Without recalculating everything, I can see that the heat to bring wood from 0F to room temperature could be up to 1% of the actual heating value of that wood. And anyone who likes numbers can see that almost half of this heat is the phase change of just the water portion of the wood. And if your wood is much over 20%, thawing the water in the wood (from 32F to 32F) will take more energy than raising the temperature of the wood AND the water from 0F to 70F! Just wait until we start comparing the heat of vaporization to the relatively minor heat of fusion (melting). Now my goal is to have the driest wood possible (at least as dry as is possible here in the dank PNW).

The big takeaway here is that moisture content of your wood affects your comfort and safety in multiple ways.

And now that my brain hurts, it's time to go outside and play with wood!

Let 'er rip!

 

[FaithfulWoodsman]

The big takeaway here is that moisture content of your wood affects your comfort and safety in multiple ways.

And now that my brain hurts, it's time to go outside and play with wood!

Yes and yes. I'm a MS science teacher, so it's been fun delving into this much pyro-physics. I must know what both of your professions are as my instincts tell me they involve engineering, physics, or chemistry. Plz tell.

 

[Hasufel]

Yes and yes. I'm a MS science teacher, so it's been fun delving into this much pyro-physics. I must know what both of your professions are as my instincts tell me they involve engineering, physics, or chemistry. Plz tell.

You're very perceptive! Chemical engineer. It's rare that I get a chance to apply my (admittedly dated) knowledge on such practical matters. Although I did get a free drink at Starbucks one time because I knew Avogadro's number...

 

[WoodyIsGoody]

Yes and yes. I'm a MS science teacher, so it's been fun delving into this much pyro-physics. I must know what both of your professions are as my instincts tell me they involve engineering, physics, or chemistry. Plz tell.

Ha! I'm semi-retired from commercial salmon fishing in Alaska and Washington, carpenter, laborer and freestyler who has been a ski bum his entire life. I've made more $$ sitting on my ass in front of my monitor playing the stock market than I've ever made using my hands and back. Otherwise I'd still be fishing. Now my wife and I just manage our one beach vacation rental on Kauai and continue to invest. My dog doesn't understand what is so attractive about my laptop (considering it doesn't have good smells or seem to do much at all). He shows more interest when I fire up my Green Egg! He loves fires, the sunny spot on the carpet (even in mid-summer, go figure) and, oddly enough, following me on my skis for miles, even when the snow is above his chest, in which case he stays in my powder tracks even if they make SS's down a steep slope. This never fails to entertain others who might chance to be close enough to observe. Because it looks like he is imitating a skier (when actually he's just being practical and trying to keep his head above the surface of the snow). But I think he has more fun than I do.

The equations and conversions here made me delve into areas that hadn't been exercised much since I was in HS and college ~30 years ago because I'm more of a back of a napkin, seat of the pants thinker.

 

[Oldman47]

So why are you guys stopping at 70ºF or 21ºC? Wood cannot burn at that temperature. I am not sure where it starts but I know that even paper will not burn until 451ºF. My bet is wood would be a bit higher. By that time you have boiled off all of the moisture, latent heat of vaporization, in either case and the BTUs to heat your wood from frozen to 70F becomes insignificant compared to making that steam and heating the wood that much. If you are going to run the numbers, why not be complete about what we do know?

 

[Hasufel]

So why are you guys stopping at 70ºF or 21ºC? Wood cannot burn at that temperature. I am not sure where it starts but I know that even paper will not burn until 451ºF. My bet is wood would be a bit higher. By that time you have boiled off all of the moisture, latent heat of vaporization, in either case and the BTUs to heat your wood from frozen to 70F becomes insignificant compared to making that steam and heating the wood that much. If you are going to run the numbers, why not be complete about what we do know?

In all this thermodynamics excitement I've kind of lost track of how this started but I think the point was to highlight the difference between loading cold wood from outside directly into the stove vs. loading wood that had reached room temperature, and that difference was on the order of 0.6% of the wood's heat value. You are right that there's a lot of additional heat needed to get the wood to its ignition temperature (and boil off the water in the process) but that would be the same in both cases (0F vs 70F wood). I don't anticipate people preheating the wood to 450F and then chucking it into the stove. Doing the math, however, would probably highlight just how much energy is needed to boil off the water, and reinforce the importance of burning dry wood.

 

[FaithfulWoodsman]

Doing the math, however, would probably highlight just how much energy is needed to boil off the water, and reinforce the importance of burning dry wood.

Bingo! That's the info to change your ways. But I already burn dry and I assume most everybody on here has been educated and is working towards that goal. Knowing what you need and how to get it are two different things. I have two year CSS beech and ash right now that are in the low 20's, some lower. But I expected nothing but teens, low at that. Split to big, not enough air and tarps that really didn't do much. Water also drains to where wood is stacked, but there's nothing I can do about that. Adjustment will be made. Found half a cord of burn now (15%) cherry to add, so all is well. But I find myself saying what was said last year when I had to supplement the last month with dead standing......."next year I'll have 5 cords of super dry wood". Ironically this year this year is worst than last (middle stacks). Next year for sure.

 

[WoodyIsGoody]

So why are you guys stopping at 70ºF or 21ºC? Wood cannot burn at that temperature. I am not sure where it starts but I know that even paper will not burn until 451ºF. My bet is wood would be a bit higher. By that time you have boiled off all of the moisture, latent heat of vaporization, in either case and the BTUs to heat your wood from frozen to 70F becomes insignificant compared to making that steam and heating the wood that much. If you are going to run the numbers, why not be complete about what we do know?

I hear you. When I have more unallocated free time I would like to do just that. The heat of fusion (ice to water) is an eye-opener but pales in comparison to the heat of vaporization. And the energy loss as the water in your wood vaporizes hurts more than the lost energy would indicate. By consuming heat, the evaporation of water cools the combustion process and causes a less complete burn. So more unburnt gases escape up your chimney without contributing to the heating of your home. And some might say, that's ok, I'll burn the less dry stuff when the weather is mild and I don't need the extra heat. But that's the worst time to burn damp wood because that's when you want to be able to burn low and slow which is precisely when you don't want your combustion cooled further. Creosote city.

Here's a brainteaser that I don't know the answer to. My ski cabin is in a PNW rainforest at 1000 foot elevation. It's quite rare for the humidity to drop below 50%, at least for any length of time. Typical humidity is close to 100% (generally 80%-100%). So how is it that my woodpile ends up at 20% humidity after a couple of years? It's a mystery to me.

 

[Oldman47]

Just try telling someone who doesn't understand the math that boiling is a cooling process. They will think you have lost all of your marbles.

 

[Firefighter938]

I've noticed a big change in my wood lately. It has been warm and wet in central Indiana for several weeks. I am burning standing dead ash that has been stacked for 1.5yrs. It was probably burnable the day I stacked it, but I didn't need it.
Anyway, it has been burning great until just a few days ago. Now on cold starts(which is happening more often because of mild temps) I'm seeing some moisture come out the ends. Not for long, and it doesn't bubble, but you can see it. It is a little more difficult to start fires also.
This is all from the same tree, the same stack, and it has been sitting in a pole barn for 2 months, so it hasn't gotten rained on.
I think the constant high humidity we have had has added moisture to the wood, to the point it is now noticeable. It only lasts a few minutes and is gone, but definitely changed the characteristics of the fire.
It is possible that the wood I'm burning now was the lower portion of the tree, or the bottom of the stack when it was outside also.

 

[FaithfulWoodsman]

Here's a brainteaser that I don't know the answer to. My ski cabin is in a PNW rainforest at 1000 foot elevation. It's quite rare for the humidity to drop below 50%, at least for any length of time. Typical humidity is close to 100% (generally 80%-100%). So how is it that my woodpile ends up at 20% humidity after a couple of years? It's a mystery to me

I've noticed a big change in my wood lately. It has been warm and wet in central Indiana for several weeks. I am burning standing dead ash that has been stacked for 1.5yrs. It was probably burnable the day I stacked it, but I didn't need it.
Anyway, it has been burning great until just a few days ago

Something tells me atmospheric pressure plays a large role in determining how RH is going to affect the drying of cellular moisture and the expansion/contraction of seasoned (burn ready) wood. Any woodworker knows humidity can drastically affect the size and characteristics of wood. My current batch was questionable already, but I've noticed it has gotten even worse since the constant bombardment of moisture in the air for about a month now. Many splits sizzle for at least 10 minutes and some even have moisture escaping through the sides under the bark, visible once it lifts. I take in a week's worth at a time and things get better within a few days.

 

[Hasufel]

Here's a brainteaser that I don't know the answer to. My ski cabin is in a PNW rainforest at 1000 foot elevation. It's quite rare for the humidity to drop below 50%, at least for any length of time. Typical humidity is close to 100% (generally 80%-100%). So how is it that my woodpile ends up at 20% humidity after a couple of years? It's a mystery to me.

I think the answer is that air and wood are different substances with different properties. Moisture in your wood is not technically humidity because it's sitting there in the liquid state, whereas in air it's a vapor. Theoretically, any liquid water will tend to evaporate if it's exposed to air below 100% RH. However, in wood, there's capillary action and other processes that cause it to hold on to some of the water. So moisture in wood reaches a certain equilibrium point that depends on the RH and maybe other factors (like air pressure perhaps?). I ran some tests here and found that firewood that's not exposed to rain can still gain weight when the humidity goes up. Another factor to consider is that you have sunlight helping; that heats the wood above the air temperature and increases the vapor pressure of the water inside, which makes it more likely to evaporate. And the more wind you have, the less likely you are to have the air in contact with wood reach saturation...so that increases drying too.

 

[Oldman47]

If you really want to get into what goes on with wood moisture content try here, but only if you are very serious about it. It makes for heavy reading but does tell you that relative humidity and wood stable moisture content are very different. The wood will hold a lot less than you might think using just RH. I find that page 3 and 4 help my understanding in the broad sense.
http://www.woodbodger.com/wp-conten...Relations-and-Physical-Properties-of-Wood.pdf

 

[Hasufel]

If you really want to get into what goes on with wood moisture content try here, but only if you are very serious about it. It makes for heavy reading but does tell you that relative humidity and wood stable moisture content are very different. The wood will hold a lot less than you might think using just RH. I find that page 3 and 4 help my understanding in the broad sense.
http://www.woodbodger.com/wp-conten...Relations-and-Physical-Properties-of-Wood.pdf

That's a fantastic resource, thanks! So per the brainteaser that @WoodyIsGoody posed, Table 4-2 shows that at, say, 70F and 90% RH, you can still dry wood down to 20.5% MC. Very interesting!

 

[Sodbuster]

I've noticed a big change in my wood lately. It has been warm and wet in central Indiana for several weeks. I am burning standing dead ash that has been stacked for 1.5yrs. It was probably burnable the day I stacked it, but I didn't need it.
Anyway, it has been burning great until just a few days ago. Now on cold starts(which is happening more often because of mild temps) I'm seeing some moisture come out the ends. Not for long, and it doesn't bubble, but you can see it. It is a little more difficult to start fires also.
This is all from the same tree, the same stack, and it has been sitting in a pole barn for 2 months, so it hasn't gotten rained on.
I think the constant high humidity we have had has added moisture to the wood, to the point it is now noticeable. It only lasts a few minutes and is gone, but definitely changed the characteristics of the fire.
It is possible that the wood I'm burning now was the lower portion of the tree, or the bottom of the stack when it was outside also.

Ditto,ditto,ditto on this, with temperatures in Michigan hovering in the 40's to near 50, I've had several cold starts, all of which take hours. If I don't let the stove go cold, I have no problem, but a cold stove in this climate is a very slow start. This is using dead Ash that has be CSS for 1-1/2 years and was 12% when I cut it.

 

[WoodyIsGoody]

That's a fantastic resource, thanks! So per the brainteaser that @WoodyIsGoody posed, Table 4-2 shows that at, say, 70F and 90% RH, you can still dry wood down to 20.5% MC. Very interesting!

Good eye on that. Humidity does drop here in the summer which helps as well.

Another chapter of the same book has more relevant info:
http://www.woodbodger.com/wp-conten...3-Drying-and-Control-of-Moisture-Content1.pdf

Sadly, no discussion of how deep freezing green wood might affect it's future drying speed. Also, the drying table (4-2) doesn't extend below 30 degrees. I've often felt that some freeze/thaw cycles contribute to better drying in my climate.

 

[Ashful]

Ditto,ditto,ditto on this, with temperatures in Michigan hovering in the 40's to near 50, I've had several cold starts, all of which take hours. If I don't let the stove go cold, I have no problem, but a cold stove in this climate is a very slow start. This is using dead Ash that has be CSS for 1-1/2 years and was 12% when I cut it.

Hours? For me, a cold start in cold weather takes 6-8 minutes from lighting match to active and engaged catalytic combustor. In mild weather, when my shorter (15 feet) chimney gets lazy, it can take up to 15 minutes, but never more. The last time I spent more than 15 minutes waiting for secondary combustion was my first year burning, when I was trying to burn poorly-seasoned wood, and even then we were looking at more like 30 minutes to reach secondary combustion. If I read your post correctly, and you're belching creo for several hours waiting for secondary combustion to kick in, something is horribly wrong!

 

[Sodbuster]

Hours? For me, a cold start in cold weather takes 6-8 minutes from lighting match to active and engaged catalytic combustor. In mild weather, when my shorter (15 feet) chimney gets lazy, it can take up to 15 minutes, but never more. The last time I spent more than 15 minutes waiting for secondary combustion was my first year burning, when I was trying to burn poorly-seasoned wood, and even then we were looking at more like 30 minutes to reach secondary combustion. If I read your post correctly, and you're belching creo for several hours waiting for secondary combustion to kick in, something is horribly wrong!

Hours may be a bit long now that I rethink it. Basically with my steel stove,if I let it get stone cold, it takes a while before it's throwing serious heat. That's starting the logs, that are cold, with Fatwood. If I catch it with some hot coals the whole process is much quicker. I guess that was my poorly made point.

 

[Ashful]

Hours may be a bit long now that I rethink it. Basically with my steel stove,if I let it get stone cold, it takes a while before it's throwing serious heat. That's starting the logs, that are cold, with Fatwood. If I catch it with some hot coals the whole process is much quicker. I guess that was my poorly made point.

Save your smaller splits for those cold starts. It does take longer if you're loading all 6" or 8" square splits on top of that kindling. Nothing wrong with an occasional box of 4" splits, for getting things hot fast.

 

[venator260]

I also like to get it inside to warm up and dry out for a week before it burn it, it makes a noticeable difference.

This is what I do. My current t basement full has been processed for 1.5 years, but has been about 7-8 stacks deep in my dad's woodshed for that time. I pick a warm day and put a bunch in the basement. I get the sizzles for about 3-4 days, and then it stops. I figure that being in the basement that stays about 70-80 degrees and about 30% RH takes off enough surface moisture that it stops being an issue. At my current rate of burning, I have about 3 weeks to a month's worth in the basement currently. It's been there since last Saturday. I stopped getting sizzlers Wednesday or Thursday.

My plan for next year is to reconfigure my space and get at least 1/2 a winter's worth in there in the fall. I'll pick my best wood, but any drying that occurs will help the burn and add moisture to the house, however little it may be.

And as another poster said, I try to pick warm days to bring in wood, but that's more about short term heat loss through the window I throw the wood in through.

 

[FaithfulWoodsman]

I get the sizzles for about 3-4 days, and then it stops.

I am getting sizzle now, but wasn't with my stuff stored for several months under shed after two years CSS. Current stuff was also 2 yr CSS but wasn't under shed until few weeks ago. I can only bring in 1.5 weeks worth, but notice a big diff after a few days. Designing a better plan for the future.