Why we talk about burning dry wood

[CrappieKeith]

Have you heard the comment I mix in green wood to get a longer burn time.
It may work that way but the btu's available drop off greatly with wetter wood. Here's a chart...

http://www.google.com/url?sa=t&sour...0_-0qS_IlYF1EjYTg&sig2=1akWnaNK_uovkJQzyRDQoA

Juca also has this link that explains HHV vs LHV which may help consumers to understand ratings when purchasing a new appliance.
The Amount of Energy in Wood

Here's another set of intel that's helpful.
In the laboratory it is possible to get a heat value of 8,660 Btu/lb from wood fuel. This "high heat value" is obtained only with perfectly dry wood with 0% moisture content and in an atmosphere of pure oxygen. For laboratory use this is a useful number handy for theoretical problem analysis. But for the practical world it is unrealistic.

When wood is alive and fresh it consists primarily of water, i.e. most of the weight is actually water. After being cut to length and stacked for a year or two the average moisture content generally drops to approximately 20%.

In the combustion process water is evaporated and the temperature is raised to flue gas temperature.

Condition of Wood Approximate Combustion Values
btu/lb kJ/kg kcal/kg
Wet 4,000 9,300 2,220
Dry 7,000 16,300 3,890
6.3 lbs dry wood = 1 Boiler Horse Power
11.6 lbs wet wood = 1 Boiler Horse Power
Moisture Content and Usable Energy
Moisture Content and Usable Energy
Moisture Content
% Energy by Volume Unit
% Energy per Weight Unit
%
0 (oven dry) 100 100
20 (air-dry) 97 81
50 (green) 92 62
100 (wet) 85 42
Note that

by volume wet wood has about 85% of the energy of oven-dry wood
by weight wet wood has less than half - 42% - of the energy of oven-dry wood
One weight unit of wood has enough energy to evaporate 6 weight units of water.

John has an excellent article here that every novice should read.
http://www.hrt.msu.edu/energy/Notebook/Burning_wood_may_offer_heat_savings_by_Bartok.pdf

 

[Laird]

Have you heard the comment I mix in green wood to get a longer burn time.
It may work that way but the btu's available drop off greatly with wetter wood. Here's a chart...

http://www.google.com/url?sa=t&sour...0_-0qS_IlYF1EjYTg&sig2=1akWnaNK_uovkJQzyRDQoA

Juca also has this link that explains HHV vs LHV which may help consumers to understand ratings when purchasing a new appliance.
The Amount of Energy in Wood

Here's another set of intel that's helpful.
In the laboratory it is possible to get a heat value of 8,660 Btu/lb from wood fuel. This "high heat value" is obtained only with perfectly dry wood with 0% moisture content and in an atmosphere of pure oxygen. For laboratory use this is a useful number handy for theoretical problem analysis. But for the practical world it is unrealistic.

When wood is alive and fresh it consists primarily of water, i.e. most of the weight is actually water. After being cut to length and stacked for a year or two the average moisture content generally drops to approximately 20%.

In the combustion process water is evaporated and the temperature is raised to flue gas temperature.

Condition of Wood Approximate Combustion Values
btu/lb kJ/kg kcal/kg
Wet 4,000 9,300 2,220
Dry 7,000 16,300 3,890
6.3 lbs dry wood = 1 Boiler Horse Power
11.6 lbs wet wood = 1 Boiler Horse Power
Moisture Content and Usable Energy
Moisture Content and Usable Energy
Moisture Content
% Energy by Volume Unit
% Energy per Weight Unit
%
0 (oven dry) 100 100
20 (air-dry) 97 81
50 (green) 92 62
100 (wet) 85 42
Note that

by volume wet wood has about 85% of the energy of oven-dry wood
by weight wet wood has less than half - 42% - of the energy of oven-dry wood
One weight unit of wood has enough energy to evaporate 6 weight units of water.

John has an excellent article here that every novice should read.
http://www.hrt.msu.edu/energy/Notebook/Burning_wood_may_offer_heat_savings_by_Bartok.pdf

No good reason to burn green wood......unless you're building a signal fire.

 

[Hedgerow]

Yeah... Kinda knew that, but couldn't resist the read... Now I have a headache... Thanks Kieth...
:beat_brick:

 

[CrappieKeith]

In that last link there was a good table of oil gas btus and how much wood it would take to make the same heat.
Maybe it was an over load of info...point made, point proven.

 

[Hedgerow]

In that last link there was a good table of oil gas btus and how much wood it would take to make the same heat.
Maybe it was an over load of info...point made, point proven.

Actually, just giving you a hard time. :msp_wink: That table was indeed interesting. Just plug the values of your local wood market and your local fuel market.

 

[Oldtimer]

A chunk of "green" red oak in on top of several dry chunks of red oak = a good bed of red coals in the AM. Sometimes the goal isn't the max possible heat output, rather, the longest possible burn time..don't need the homestead to be 80* overnight, but it's nice to have a little seed left in the AM.

Also, if all you have access to is green wood, then green wood becomes the best damn thing since canned beer.
And if you know what you are doing, you can get the fire to a point where the green you put in is "dried" by the wood burning under it...and you can get massive heat out of green wood. I should know, I've done it a couple thousand times in my 40+ years of stove tending.

 

[laynes69]

Theres nothing good about burning green wood. It puts excessive moisture in the firebox which lowers the firebox temperatures and will allow for the formation of creosote in the chimney. Green wood becomes the next best thing when its been seasoned. We burn in a modern furnace which is automatically controlled by a thermostat. If the wood isn't seasoned correctly, the burn times will suffer. The fire has to cook off the moisture, which in return robs btus from the firebox. That in return calls for the thermostat to open and compensate. When the wood is dry on the otherhand, the firebox temperatures remain higher. Less air is needed to maintain a hotter fire therefore more btus are put into the home. With modern woodburners and seasoned wood burning green wood is a thing of the past. I see people do it around here and judging from the amount of wood they burn and the smoke they produce it shows.

 

[Hedgerow]

A chunk of "green" red oak in on top of several dry chunks of red oak = a good bed of red coals in the AM. Sometimes the goal isn't the max possible heat output, rather, the longest possible burn time..don't need the homestead to be 80* overnight, but it's nice to have a little seed left in the AM.

Also, if all you have access to is green wood, then green wood becomes the best damn thing since canned beer.
And if you know what you are doing, you can get the fire to a point where the green you put in is "dried" by the wood burning under it...and you can get massive heat out of green wood. I should know, I've done it a couple thousand times in my 40+ years of stove tending.

I won't disagree with this. And oldtimer gets rep for being the contrarian we know and like............ I will go on record as one who preferes dry wood... VERY dry wood... For my own reasons... Mostly, because I want to wear shorts and flip flops when I come in for the night... I want that bugger HOT!!! For coals? I throw a chunk of hedge in before retiring for the night.:msp_wink:

 

[Iron man]

I'm not picky; cant complain when I'm heating my house for free not counting the cost of collecting/cutting and splitting it.This last winter I burned wood that had been split for 3 years and it was awesome because it literally fired up with a small piece of lit cardboard.When its not seasoned as well I make sure to keep in a few pieces even if there not needed.I do like the smoke pouring out the chimney.To me its a signal saying I don't support terrorist.

 

[TMFARM 2009]

Theres nothing good about burning green wood. It puts excessive moisture in the firebox which lowers the firebox temperatures and will allow for the formation of creosote in the chimney. Green wood becomes the next best thing when its been seasoned. We burn in a modern furnace which is automatically controlled by a thermostat. If the wood isn't seasoned correctly, the burn times will suffer. The fire has to cook off the moisture, which in return robs btus from the firebox. That in return calls for the thermostat to open and compensate. When the wood is dry on the otherhand, the firebox temperatures remain higher. Less air is needed to maintain a hotter fire therefore more btus are put into the home. With modern woodburners and seasoned wood burning green wood is a thing of the past. I see people do it around here and judging from the amount of wood they burn and the smoke they produce it shows.

ok now, its more of a longer burn time then puff its done!! i agree at night time we put a little more greener wood in to lengthen the burn time.. keeps from loading the stove at night, say 3:00 am.
to each their own but it works for me.. and yes i dont care if the stove throws smoke and you can see that i am burning wood instead of paying the electric company.. i say let it smoke its a badge of honor to all that burn wood for heat..we work hard to harvest it cut split and handle it, so we like some smoke cause we aren't lazy just paying some one else for heat.....besides i like the smell of a good smoky fire..
:look_down:

 

[046]

Kieth is dead on the money in terms of heat value from dry wood vs wet.
what you burn the wood in also makes a difference.

most modern wood stoves favor dry woods and will not tolerate greed woods.
they throttle down burn rate so low, long burn times are not the issue. BTU output is.

old style stoves like my JUCA with open burn. length of burn becomes as important, if not more than BTU output of wood. one of my favorite methods is to get a fire good and hot with seasoned Oak. then switch to green Oak. have proven long ago my JUCA burns green wood very clean with almost NO smoke out of chimney.

if you can see smoke out your chimney then something is not getting completely burned. it's not rocket science. but some make it that way. all fires will smoke when getting up to temps... most if not all EPA rates wood stoves will emit next to no smoke after getting up to operating temps.

my guess is most EPA rated stoves will not burn green wood cleanly. simple test, get your stove up normal operating temps, then throw in some green wood. watch your chimney after getting the green wood burning good as it's going to. all while keeping an eye on your chimney's output. if your chimney doesn't look exactly like it does burning seasoned wood with almost no smoke. then green wood is not for you.

I've gone 4+ seasons without cleaning my chimney after burning LOTS of green wood. almost NO creosote buildup if you are getting almost complete burn. don't get me wrong I'll check my chimney each season just for safety. used to check it twice a season when first getting started burning.

A chunk of "green" red oak in on top of several dry chunks of red oak = a good bed of red coals in the AM. Sometimes the goal isn't the max possible heat output, rather, the longest possible burn time..don't need the homestead to be 80* overnight, but it's nice to have a little seed left in the AM.

Also, if all you have access to is green wood, then green wood becomes the best damn thing since canned beer.
And if you know what you are doing, you can get the fire to a point where the green you put in is "dried" by the wood burning under it...and you can get massive heat out of green wood. I should know, I've done it a couple thousand times in my 40+ years of stove tending.

 

[TMFARM 2009]

we use an older earth stove insert... its not politically correct or EPA approved to today's standards.. but it works fine and has heated this house since 1980..i dont worry about the smoke, if its smoking its not out yet...:hmm3grin2orange::hmm3grin2orange:
besides,i like to do my share of global warming..

 

[TMFARM 2009]

just look at it this way, if global warming increases then you wont have to use as much firewood to heat the house. this = less work = more beer time = a better way to spend the day...:hmm3grin2orange::hmm3grin2orange:

 

[Oldtimer]

It should be noted here that I live in a house that was built when we still had a King named George who like to tax our tea. It takes a lot of heat to keep your toes warm in this house.
I can not afford to let the fire go out, and with my Ashley "airtight" it will if I use dry wood before turning in for the night. A few sticks of green is the only way to have seed come the 3AM bathroom trip. And I drink a bottle of Vitamin water before bed for this purpose.

Back in the day when I was a young single man, I'd go to bed with a half can of pepsi on the night stand, and wake up to find it frozen solid in the morning. OLD farm house. Round field stones under the sills, no granite slabs, and certainly no concrete.
How I love it.

 

[lfnh]

It should be noted here that I live in a house that was built when we still had a King named George who like to tax our tea. It takes a lot of heat to keep your toes warm in this house.
I can not afford to let the fire go out, and with my Ashley "airtight" it will if I use dry wood before turning in for the night. A few sticks of green is the only way to have seed come the 3AM bathroom trip. And I drink a bottle of Vitamin water before bed for this purpose.

Back in the day when I was a young single man, I'd go to bed with a half can of pepsi on the night stand, and wake up to find it frozen solid in the morning. OLD farm house. Round field stones under the sills, no granite slabs, and certainly no concrete.
How I love it.

LoL. Yup. and then there's the story of the snake, the mouse; first hard frost; and the week before Thanksgiving...

 

[Iron Head]

You're scaring me oldtimer!
Would a modern high efficiency stove give you more burning time with dry wood?
You're right about burning whatever that is available.
i did it for a year but I don't like the smoke and the dirty pipe.

 

[CrappieKeith]

I bet I get slapped for this

ok now that we have heard what some do...I'll make another point.

I put a green piece on top to get the all night burn..it's not like we need the house at 80.

If you had a furnace that was electronically controlled you could turn down the stat and control it.
Stoves seem to fall into that all or nothing type of operation. the room they are in is hot as hades.
okokokokokok I know some homes are smaller or they have no ducting or whatever else the reason for a stove in lieu of a furnace....I also know a guy will do what a guy will do.
As the OP...
the main reason was to put out some info. When all stoves& furnaces are EPA listed dry wood will be imperative.

 

[mtfallsmikey]

Keith:
I'm sure you've gotten a peek inside of a Yukon after green wood is burned in it.
Real ugly! And almost impossible to totally remove the goo....

 

[gwiley]

Another vote here for judicious use of less seasoned wood.

I run an OWB and rely on less seasoned wood for longer overnight burns. Well seasoned wood produces more heat, but too quickly for some scenarios at our house.

I live in the middle of nowhere - no one to complain about smoke and chimney fires are just my way of cleaning the flue without getting dirty (OWB is not next to or in the house).

One other scenario - seems to always come up near the end of the season - run out of seasoned wood, whatcha gonna burn? Is less seasoned wood better than air? Well, some BTUs are better than none.

 

[CrappieKeith]

Keith:
I'm sure you've gotten a peek inside of a Yukon after green wood is burned in it.
Real ugly! And almost impossible to totally remove the goo....

You got that right...at .03" of water column for a draft speed you just can't burn wet wood hot enough to burn clean.
That's another reason we try to be involved in the sizing of it too. Too many guys have that Tim Allen/Tool Time mentality....more power or bigger is better. Their experiences tell them that the wood burners they are used too usually don't heat what the manufacture says it will heat so they want to oversize them...not so with a Yukon furnace. Also a smaller hotter fire is way more efficient than a large smoldering fire.