Does the firewood split size matter?

[Stubby]

Our wood stove is small...a Vermont Castings Resolute, but it heats our small home very well. Because it's small, I tend to split the firewood kind of small...personal preference.

I've wondered, though, if this makes a difference overall.

Hypothetical situation...all logs are 16" in length, same age, etc. If I split a 12"x12"x16" (rectangular) log into four 6"x6"x16" rectangular logs vs. sixteen 3"x3"x16" rectangular logs, overall, what difference would it make, burn-wise?

I'm thinking that if I wanted to get a fire going faster, the 3x3's would do that. If I wanted a slower burn, the 6x6's would do that.

But, if I didn't care about any of those things, doesn't it all come down to BTU output? A stove full of 3x3's would burn hotter, producing more BTU's for a shorter duration than a stove full of 6x6's.

In the end, let's say that I burned twelve of the 6x6's, or forty eight of the 3x3's (so, same volume of wood..).

Without changing any of the stove's adjustments, would there be a total BTU difference between the different size cuts?

Just curious, that's all....

Rich

 

[NSEric]

I can get more wood in the stove when I use some small ones, with all larger wood I can never get the stove completely full.
I care more about that than btu per stick so I split some of my wood up pretty small.
All small wood is fine but to save some time splitting, I dont split it all up to about 3x3, I mix it up size wise, as long as I can get the stove full so it goes all day when im gone im happy.

 

[Stubby]

Yes...3x3 is small, I just used that size for the conversation. I also mix whatever sizes and throw them in the stove...

Rich

 

[LawrenceK]

I think the btu output from one piece of wood will be the same no matter how you slice it. The difference will be in how long it takes to spend that btu. The smaller you split it up, the faster it emits its btu load by burning really hot for a short time. The same piece of wood in larger form will emit the same btu load at a slower rate while not burning as hot. No matter how you burn it or under what conditions, it can't put out any more or any less than its potential. My stove is pretty small (Jotul 602N), too. The fire usually ends up with a bed of hot coals and two large pieces when fully loaded. I never really think about btu output. That would drive me crazy. I have a thermometer on the stovepipe and I worry more about over-firing, which seems to be the tendency with the little Jotul. When you're heating all winter with a wood burner, it's like your married to the darn thing. But I guess it wouldn't be any fun if all you had to do is light it and leave it alone.

 

[Stubby]

I don't focus on BTU's. That was just part of the conversation to help describe my question in the first post.

I only posed the question because when I'm splitting the wood, I wonder to myself, if I'm wasting time splitting a lot of the logs an extra time, for what reason, exactly.
Like, I'll have a 6x6 split log, look at it, and split it once more. I know it's fine as a 6x6, but....

Rich

 

[Patrick62]

I tell my customers, I split wood in 3 sizes...
(does this sound like the 3 bears?)
OK, I pick up a round... and in a brief instant decide to either split it half, or thirds. Based upon knots, size, etc.
I pick up a larger round, it goes to thirds... some of the time. SOmetimes I rotate it 60 degrees and push it again
Making it into 6 pieces... (it's a triangular wedge on splitah)
Ok, the result is 1/3 of them are smaller, like 3 inch stuff, 1/3 of them are middle size stuff 5 inch ish.
And 1/3 of them are what I call "large" like 6 inch one way and sometimes 7 to 8 the other way.

Unless I know the customers stove. Small stove, and reduce the overall size some.

Madness sets in after about a thousand cords and nothing to do but lift, split, toss. Greener stuff? little smaller.
Interesting that if you position it a knot will break right down the middle. Some knots are fun to send the blade right across it, with greener stuff. Breaks more fibers, makes a nice burning chunk.

Then I pickup a block that is a bit long... drop it across the beam, 22 tons and sever the thing! split and toss, call it "kindling"

There are no stupid questions.
but the answers could be

 

[Stubby]

I tell my customers, I split wood in 3 sizes...
(does this sound like the 3 bears?)
OK, I pick up a round... and in a brief instant decide to either split it half, or thirds. Based upon knots, size, etc.
I pick up a larger round, it goes to thirds... some of the time. SOmetimes I rotate it 60 degrees and push it again
Making it into 6 pieces... (it's a triangular wedge on splitah)
Ok, the result is 1/3 of them are smaller, like 3 inch stuff, 1/3 of them are middle size stuff 5 inch ish.
And 1/3 of them are what I call "large" like 6 inch one way and sometimes 7 to 8 the other way.

Unless I know the customers stove. Small stove, and reduce the overall size some.

Madness sets in after about a thousand cords and nothing to do but lift, split, toss. Greener stuff? little smaller.
Interesting that if you position it a knot will break right down the middle. Some knots are fun to send the blade right across it, with greener stuff. Breaks more fibers, makes a nice burning chunk.

Then I pickup a block that is a bit long... drop it across the beam, 22 tons and sever the thing! split and toss, call it "kindling"

There are no stupid questions.
but the answers could be

I feel that splitting wood is kind of therapeutic and somewhat boring (at least the one-log-at-a-time, homeowner version...), which gives the mind a chance to ponder things.

You are a testament to that, as well...

Rich

 

[ElevatorGuy]

My VC stove isn’t huge but not small either. First year or two after we installed it I had pretty much all smaller splits. 6-8 splits in a typical full load, had trouble maintaining a fire for 8 hours. I changed how I split wood and now a full load is 4 or 5 splits, lasts much longer.

I do split some junk wood small for starter kindling, This year it was a poplar tree I took down. 3-4 small 2x2x18 or so gets it going quickly and establishes a nice draft.

 

[farmer steve]

For myself I make a mix of all sizes. Some smaller to get the fire going and some for overnighter. For my selling wood I try and make uniform splits. Nothing overly large. Must work because I get positve comments on the sizes.

 

[Stubby]

I know that when we started burning wood, mid 1980's, there were times that I bought firewood.

It appeared that the seller would take whatever diameter log and run it through a 4-way splitter. Done.

So, a lot of the splits were a lot larger ( diameter-wise) than I preferred. And I didn't have a log splitter, so I had to hand split the ones that were too fat.

Takes a lot of the convenience out of buying it split and delivered.

Rich

 

[Rich 07830]

We have a Napoleon 1400 that came with the house. It's not great for long burns. Loading it with bigger chunks definitely works better!
What shape splits do people strive for? I like mostly rectangular, big splits.

 

[firekindler]

Our wood stove is small...a Vermont Castings Resolute, but it heats our small home very well. Because it's small, I tend to split the firewood kind of small...personal preference.

I've wondered, though, if this makes a difference overall.

Hypothetical situation...all logs are 16" in length, same age, etc. If I split a 12"x12"x16" (rectangular) log into four 6"x6"x16" rectangular logs vs. sixteen 3"x3"x16" rectangular logs, overall, what difference would it make, burn-wise?

I'm thinking that if I wanted to get a fire going faster, the 3x3's would do that. If I wanted a slower burn, the 6x6's would do that.

But, if I didn't care about any of those things, doesn't it all come down to BTU output? A stove full of 3x3's would burn hotter, producing more BTU's for a shorter duration than a stove full of 6x6's.

In the end, let's say that I burned twelve of the 6x6's, or forty eight of the 3x3's (so, same volume of wood..).

Without changing any of the stove's adjustments, would there be a total BTU difference between the different size cuts?

Just curious, that's all....

Rich

Despite the size of the stove, I usually aim to have most of my wood fit easily on a bed of coals. Much less splitting, more burn time, and many of the pieces get smaller as because they split themselves smaller as I go. In other words, sometimes I'll get three pieces inadvertently when trying to make two. Then I have enough smaller pieces to mix in. Keep in mind I also live in a milder winter climate than many. It usually only dips below freezing a few times each winter, and usually not very much. I usually use Douglas fir limbs and bark that has sloughed off the seasoned pieces (stored in boxes) to help take the chill out in the mornings so don't usually need much smaller hardwood.
Keep in mind that fatter pieces take longer to season fully than smaller ones.

 

[Mad Professor]

Little stuff on the top big stuff on the bottom. Depending on stage of the fire you need both. Also to pack the stove full when you need to. My stove takes 30" splits.



I also keep a big plastic tote full of broken up sticks/branches ( tiny to ~ 2") to start fires or get the coals going again, along with a trash can of dried white pine cones.

Stoves are not as fussy to size (big) if the wood is fully dried

 

[pdqdl]

I think the btu output from one piece of wood will be the same no matter how you slice it. The difference will be in how long it takes to spend that btu.

Close, but not quite. Thermodynamic rules apply, even when burning wood.

1. More heat is extracted (in general) from a burning peice of wood when it is combined perfectly with the right amount of oxygen. So... keep that firebox HOT. This will reach the necessary combustion temperature to break down all the wood molecules and get them to shake hands favorably with the oxygen. Cold fires are smoky fires! Smoky fires lose a lot of efficiency. In my experience, it can me damned difficult keeping the box hot with only a few big logs in it. It's nearly impossible to do at startup, as we have all discovered.
2. When the combustion chamber is hottest and the exhausted gas temperature is the lowest, only then will the maximum heat be captured. A roaring hot fire with a box full of small kindling might be burning efficiently, but an unnecessary amount of heat is likely to be going up the flu instead of heating your house.
3. Even the ratio of carbon monoxide to CO2 plays a role in the final energy capture, so choking back a hot fire with the damper might not produce any smoke, but there will almost certainly be more carbon monoxide expelled, and measurably less heat released. If there is too much fresh air entering the combustion chamber, the fire burn ratio will yeild more CO2, but any excess air will cool the chamber and otherwise reduce the chamber temperature. The hotter the box, the more rapidly the heat will be transferred into the room holding the firebox. Provided, however, that you don't make more heat than can be captured by the heat exchanger.

Getting the burn exactly right is rather challenging. Too big or small of sticks, too much or too little, and all of a sudden, that stove isn't throwing quite as much heat as you know it can do.

 

[9050LX]

Been burning a lot of sweetgum this year. After curing the bark falls off. Makes good starter kindling, along with buckets of noodles from a year or so prior.

 

[Chainsaw Pete]

I think @pdqdl did a good job of answering your question but he indirectly answered:
"In the end, let's say that I burned twelve of the 6x6's, or forty eight of the 3x3's (so, same volume of wood..). Without changing any of the stove's adjustments, would there be a total BTU difference between the different size cuts?"

The answer is Yes, because different size chunks will require that fine tuning to provide the right amount of air. You nailed it that small pieces will burn hotter - more surface area is exposed to the incoming air but a fast burning fire will require more operator attention than a slower fire. And as pdq said, large pieces of your log will burn cooler and less efficiently. Your job as the stoker is to choose the right size for your stove in order to maximize the heat and minimize your labor.

 

[JRM]

One thing not mentioned, which is likely obvious to everyone here is the larger pieces will take longer to properly season. This isnt an issue if you get out ahead of your stack by at least 1.5 - 2 years.

 

[Stubby]

Speaking of dampers...I was having a discussion with a guy (Steve), years ago, about burning wood. I will say, that I'm not the guy that studies all the science behind every aspect of this subject..most of my "knowledge" is from trial and error.

Once I have a nice fire going, and a bed of coals established, in my mind, I feel that I get more heat out of the stove with the damper closed.

Steve disagreed with me. He felt that with the damper open, more air can be brought in (through the thermostat, etc..) to allow for a hotter fire.

I get that, but, I also feel that heat is going up the chimney. With the damper closed, it stays in the stove, emanating into the room. He wasn't convinced...

Thoughts?

Rich

 

[Tim in NY]

I always try to find the biggest pieces I can when its really cold overnight. No science to back this up, but to me it seems that the larger pieces, especially unsplit rounds last the night through better. I do not care about heat output as much as having coals left in the morning to refill and quickly get the stove hot again. And I try to cut a couple ironwood trees every year and stack them strategically so I can get to them by middle of January. I do have to keep moving those until I need them, but it just makes me feel better. I have 2 large ironwood pieces left I did not need this year. They will go on top of the 2nd row in the woodshed this spring and probably bet moved 3 or 4 times before I use them.