Why Dry Wood?

[Trooper]

I've been lurking here a while in prep for the purchase of my first-ever stove. Great forum.
What is clear to me is that most problems are caused by unseasoned wood. I've also read that dry wood is required because of the newer "EPA" stoves.

Why do the newer stoves require seasoned wood?
Can wood ever be too dry?

Thanks,
Dan

 

[fabsroman]

I've been lurking here a while in prep for the purchase of my first-ever stove. Great forum.
What is clear to me is that most problems are caused by unseasoned wood. I've also read that dry wood is required because of the newer "EPA" stoves.

Why do the newer stoves require seasoned wood?
Can wood ever be too dry?

Thanks,
Dan

Nope, wood can never be too dry. Just spent the last 15 minutes trying to get a fire started with less than optimally dried wood. What a pain. Once I get my new garage built, I am going to get years and years ahead of this stuff because burning even 25% moisture content wood SUCKS.

 

[Lumber-Jack]

I've been lurking here a while in prep for the purchase of my first-ever stove. Great forum.
What is clear to me is that most problems are caused by unseasoned wood. I've also read that dry wood is required because of the newer "EPA" stoves.

Why do the newer stoves require seasoned wood?
Can wood ever be too dry?

Thanks,
Dan

Although the older non-EPA stoves also benefit greatly from well seasoned wood, the newer EPA stoves are designed with the ability to run much cleaner and more efficiently, but they can only reach their full potential if they are run properly and the firewood is within the designed moisture content parameters. You can burn poorly seasoned wood in EPA stoves, people do it all the time, you just can't expect to reap the benefits that they are designed to give, like 70% lower particle emissions, longer burns, and the ability to heat the same space with 1/3rd less wood.
In old smoke dragon stoves the only way to get long burns is to get the fire going good and choke them right down so the fire is smoldering. This will give you longer burns, but you greatly reduce the amount of BTUs the stove can produce because much of the woods fuel is lost up the chimney as smoke without being burnt and consequently the particle emissions also go through the roof.
In and EPA stove you start the same way, get the fire going good, but when you shut down the main air supply there is still a secondary air supply that feed either the Catalytic converter, or the re-burn tubes, and much of the un-burned fuel that would normally be lost up the chimney gets re-burned and generates heat that would have otherwise been lost. However for these things to work you must maintain a certain temperature in your stove, and if your firewood is too wet the moisture evaporating from the wood robs heat from the secondary fire or cat and they will fail to work properly, and you will have lost any benefit that these improved designs can give you.

As for wood being too dry, it can happen, but it's not that common as most wood dried in the open air just doesn't get that dry. Basically if you did have wood that was too dry it would be similar to burning too much kindling in your stove, as the fire got hot the wood could start to off gas quicker than the secondary burners could supply oxygen and you would again get a lot of un-burned smoke going up the chimney and loose some efficiency, and if you opened the main air control to supply the extra oxygen necessary to cleanly burn the extra fuel getting off gassed you could possibly over fire your stove.

Anyway, that's how I understand it.

 

[tigeroak]

You get more heat out of dry wood than green . No wood can't get to dry to burn. Just here the other day a guy/woman burned some stuff that was , if I remember right, was 25 years old and burned just fine

 

[Trooper]

Anyway, that's how I understand it.

Thanks LumberJack, what you say makes good sense. My question about wood being too dry comes from my being in Arizona...things can get pretty dry here!

 

[Woody Stover]

My question about wood being too dry comes from my being in Arizona...things can get pretty dry here!

I saw that and was wondering the same thing. It looks like your average equilibrium moisture content could be well down into the single digits, whereas mine is around 13%. I wonder if there are certain stoves that would work better with drier wood; Models that perhaps allow less combustion air, while still allowing adequate secondary air to burn the smoke completely. Seems like a stove with a separate secondary air control, like my Dutchwest 2460, would be advantageous (you could modify the primary air intake to be able to cut it more.)

(broken link removed)

 

[Lumber-Jack]

I also live in a dry climate, the standing dead lodgepole trees I cut are <20% MC at the bottom and way drier at the tops, often showing no reading at all on my moisture meter, so I have had to deal with wood that is "too dry". Of course getting it to burn is not the problem, but getting it to burn cleanly without over firing the stove is the trick.
I first realized that wood could be too dry when I would load it up with some of this dry wood burn as usual and end up having smoke come out the chimney because the wood was off gassing too quickly. If I tried to opening the primary air more the smoke would disappear, but stove would start getting too hot, so I'd have to turn it back down again and just live with a bit of smoke coming out the chimney.
There is a way I could cleanly burn this very dry wood without over firing the stove though, and that was to simply not load up the box so much. Smaller loads is the key. With smaller loads the fire in the box wouldn't get as hot, and I even with the main air shut right down the secondary air is able to supply enough oxygen to keep up with the smaller fire and burn cleanly (no smoke). It's sort of ends up working more like a pellet stove with a small hot fire. The down side it you get shorter burns and less BTU output, so it's sort of a compromise.
So, it's not that dry wood won't burn, it's just that you have to burn it a little differently if you want it to burn cleanly and not over fire the stove, like I said earlier, you have to treat it like burning kindling, or kiln dried wood.

 

[Trooper]

It looks like your average equilibrium moisture content could be well down into the single digits, whereas mine is around 13%. (broken link removed)

Thanks for the EMC data, Woody! This confirms my perception that my wood is pretty dry, even immediately after cutting. And I'm guessing that after one summer here most of it would be seasoned. I have a moisture meter on order to verify this.

Is there any way to add moisture to CSS wood?

 

[Jon1270]

Really well put, Randy.

Is there any way to add moisture to CSS wood?

Aside from throwing it in a pond, you might store it in a cool, shady area rather than in the sun.

 

[Backwoods Savage]

I've been lurking here a while in prep for the purchase of my first-ever stove. Great forum.
What is clear to me is that most problems are caused by unseasoned wood. I've also read that dry wood is required because of the newer "EPA" stoves.

Why do the newer stoves require seasoned wood?
Can wood ever be too dry?

Thanks,
Dan

Welcome to the forum Dan.

Good to hear you've been lurking for a while and gathering information before your first purchase. Most parts of Arizona are indeed very dry as we learned after wintering there for 5 winters. No doubt the wood will dry much faster there not only because of the dry air but the intense heat too.

Why do the newer stoves require seasoned wood? Well now, I'm going to tell you that even 50 years ago stoves required seasoned wood. That is, dry wood. However, just because they required dry wood did not mean most folks burned dry wood. Some old time "wisdom" or supposed wisdom has been passed down year after year and still is being passed down. Then some folks are amazed when they also find that junk printed in books and reports! Yes, we see it all the time, just like the supposed "wisdom" that one should not burn pine in a wood stove. This is why it is bad for some folks to get a little knowledge and then think they know right. After all, some of this information comes from universities and almanacs. No matter because most of it is still pure baloney.

For wood to burn right in any stove requires it to be relatively dry. The pros say less than 20% moisture. The Backwoods Savages says that every one should be 3 years ahead in their wood supply and then not worry if the wood is ready to burn or not; it will be. It will solve over 90% of all wood burning problems and you'll use less wood to get the same or more heat. That also means you save dollars but the biggest benefit is that you have a warm house and that is the ultimate goal in wood burning.

If wood can be too old or too dry, I have not yet seen it. We regularly burn wood that is from 3 to 7 years or more in the stack. We keep our house 80 degrees or more all winter and we rarely clean our chimney. Thanks to dry wood and a super clean burning stove, we keep nice and warm.

 

[PapaDave]

Dennis should package and sell this spiel/mantra.
He'd make a fortune.

 

[Trooper]

Welcome to the forum Dan. Good to hear you've been lurking for a while and gathering information before your first purchase.

Thanks Dennis! I've been finding that this lurking is making me smarter than some of the dealers and installers I have been talking to.

Yes, we see it all the time, just like the supposed "wisdom" that one should not burn pine in a wood stove.

Prior to my joining the forum, I was victim of the "Don't burn pine" advice. This worried me, as we have a LOT of pine where I am. Now I don't worry so much.

 

[mywaynow]

Keep to larger splits if the wood is "too dry". Burns slower which may offset the low mc.

 

[Backwoods Savage]

Keep to larger splits if the wood is "too dry". Burns slower which may offset the low mc.

What is "too dry" wood?

 

[mywaynow]

Hence the quotes around the term. Not sure I have ever touched a piece that is too dry.

 

[Scols]

It seems like most stove dealers and some manufacturers and others in the biz preach that hardwoods only need a year to season. Thats why I always thought I was ahead of the game.

 

[Lumber-Jack]

What is "too dry" wood?

I've tried to explain "Too dry wood", but perhaps John Gulland of woodheat.org explains it better.

Can Firewood Be Too Dry?

Yes, although it is not a common problem

Properly seasoned firewood still has a fair amount of water in it, say 15 to 20 percent of its weight. That water regulates the combustion process along with a few other factors like piece size, load configuration and combustion air supply.
The higher the fuel moisture, the slower the wood breaks down when heated because of all the heat energy soaked up in boiling the water out of the wood and raising the temperature of the steam.
Conversely, the dryer the wood, the more quickly it breaks down when heated. By breaking down, I mean the vaporization of the volatile components of the wood; that is to say, it smokes. The dryer the wood, the more dense is the smoke at a given heat input rate.
Since wood smoke is fuel, we want to burn it as completely as possible and that means mixing with adequate oxygen in the combustion air. The problem is that a firebox load of very dry wood produces far more smoke than the air supplies of stoves are designed to provide. Besides, even if you could supply enough air, you would produce an inferno that would howl in the stove and make everyone in the house nervous. Fires that intense can seriously damage the stove's innards. Wood that is very dry produces a fire that is hard to control without making a lot of smoke.
Kiln-dried wood is down around 10 percent moisture. Depending on climate and conditions of storage, normal firewood won't dry down to kiln-dried moisture because of normal outdoor humidity. For example, I've never measured wood below about 14 percent in my firewood supply. But I suppose that firewood could get very dry by natural seasoning in desert conditions. Or firewood stored in old barns, which are like kilns in hot summer weather.
The right band of firewood moisture is between 15 and 20%. When you get much over 20% you start to see symptoms of sluggish ignition and the inability to turn down the air without extinguishing the flames. Towards 30% the wood sizzles and fires are very sluggish and it is hard to get a clean burn until the wood is almost to the charcoal stage. Above 30% water bubbles from the end grain when the wood is heated and it is very hard to burn at all. Species like poplar/aspen, which have very high native moisture content are virtually non-combustible when not adequately seasoned.
The main difference between EPA low-emission certified stoves and conventional stoves is that you can turn down EPA stoves for a long burn without extinguishing the flames. That is, they are better at producing a clean, controlled fire. But they are designed for wood that has a moisture content of twenty percent plus or minus one or two percent. Once you go far outside this band, their emission rate goes up. So even the best wood stove's performance will suffer if the wood is not in the right moisture range.
If you have some very dry firewood, like kiln-dried cut offs or old wood stored in a hot place, mix it with regular firewood to raise the moisture content of a full load.
JG

 

[Lumber-Jack]

I guess unless you live in an area that has a very dry climate, and experienced "too dry" wood, first hand it is hard to fathom the concept. Even John Gulland, in his blurb that I quoted above, states that he has never measured below 14% MC in his own firewood supply, and yet accurately describes the problems with too dry wood and goes on to concedes that it would be possible in dryer climate regions. Perhaps his own experience with "too dry" wood was with kiln dried wood?
Let me ask those who still doubt that cord wood can get too dry, how many of you take a fire extinguisher with you when you are out cutting firewood? I do, in fact it is a legal requirement of the firewood permit that I must obtain before heading out into the bush to cut my wood. (broken link removed to http://www.for.gov.bc.ca/dos/dist_docs/Docs/Firewood%20FUP%202014%20with%20signature.pdf). It is for good reason they put that prerequisite in the permit, in fact at certain times of the year when there is an extreme risk of forest fires locally we are banned from doing any firewood cutting at all, even if you do have your fire extinguisher.
I was born in this area and have lived here most of my life, but I have lived and stayed in other places and have come to realize that much of the world is much wetter and much more humid. In fact, I often drive 200 miles West of here out to Vancouver area, and have lived for a while on Vancouver Island where it is about as different a climate as you can imagine. Firewood stored outside there is more apt to grow moss then it is to dry out, and you'd be more concerned about carrying rain gear than a fire extinguisher when out cutting your firewood.

Yes wood can get "too dry", but as John Gulland says, it's just not a common problem, but that doesn't mean it's not real. Nor does it mean you can't burn the wood, it just means it has it's own set of potential problems that need to be addressed, and in the end, I'd much rather be burdened with wood that is too dry than too wet.

 

[Jon1270]

If you average the typical high and low relative humidities in January and July, most of the US is a lot like Michigan. Grand Rapids has an average outdoor relative humidity of about 73%, which means the equilibrium moisture content of wood stored outside is around 14%. But there are some exceptionally dry places. Yuma, AZ, for example, has an average RH around 39%, so the EMC of firewood stored there is closer to 7%.

 

[Lumber-Jack]

It's also worth noting that the dryer climates are also devoid of typical hardwoods like oak, so we are talking mainly softwoods like pine. These woods tend to release and absorb moisture quicker. Locally our wet seasons are winter and spring, which is when our wood would be absorbing most of the ambient moisture. Our dry seasons are summer and fall, and typically by the end of fall is when our wood would be the driest, and likely end up being drier than the "average" relative humidity, which is also probably true for places like Arizona where the OP Trooper is from.

 

[Trooper]

Let me ask those who still doubt that cord wood can get too dry, how many of you take a fire extinguisher with you when you are out cutting firewood? I do, in fact it is a legal requirement of the firewood permit that I must obtain before heading out into the bush to cut my wood. (broken link removed to http://www.for.gov.bc.ca/dos/dist_docs/Docs/Firewood%20FUP%202014%20with%20signature.pdf). It is for good reason they put that prerequisite in the permit, in fact at certain times of the year when there is an extreme risk of forest fires locally we are banned from doing any firewood cutting at all, even if you do have your fire extinguisher.
.

You are exactly right Lumber-Jack. In Arizona I can count on being legally banned from cutting from about Memorial Day through July 4th every year. Too much spark risk, and not a law you want to break. I sure don't want to be responsible for another half-million acre fire. That's why I need to get cutting soon

 

[Trooper]

It's also worth noting that the dryer climates are also devoid of typical hardwoods like oak, so we are talking mainly softwoods like pine. These woods tend to release and absorb moisture quicker. Locally our wet seasons are winter and spring, which is when our wood would be absorbing most of the ambient moisture. Our dry seasons are summer and fall, and typically by the end of fall is when our wood would be the driest, and likely end up being drier than the "average" relative humidity, which is also probably true for places like Arizona where the OP Trooper is from.

Dead-on again, Lumber-Jack. We do have some oaks, like Arizona oak, and one that looks a little like black walnut, and alligator juniper which smells nice when burned (it's a member of the cedar family)....And LOTS of ponderosa pine.

 

[Woody Stover]

I need to get cutting soon

And then cover your wood, top and sides, with a tarp to keep it from drying too much. If need be, you can put a bucket of water under the tarp with the wood, refilling it when necessary.

 

[Lumber-Jack]

And then cover your wood, top and sides, with a tarp to keep it from drying too much. If need be, you can put a bucket of water under the tarp with the wood, refilling it when necessary.

That might actually work.

 

[oldspark]

Lumber-Jack, you explained it very well and I agree, just for most people they wont see would that dry, be careful you'll give BWS a stroke.