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Old 01-19-2008, 07:53 PM
Status: "Apple Pie!" (set 6 days ago)
 
Location: Cary, NC
19,560 posts, read 30,982,095 times
Reputation: 16566

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With snow and sleet coming to town, I slipped out and bought some firewood yesterday.
Started a fire in the fireplace and had a hard time keeping a flame going. The wood was green.
Green wood smolders and will not burn hot enough to heat up the flue and keep the draft strong. And by smoldering, it makes more smoke than dry wood. So we had a little smoke backdraft into the house.
I had some dry wood, which actually I had bought at the grocery store. I put it on the smoldering fire, and quickly had a blaze and no more backdraft.

Pine and other softwood fuel should also be avoided, as it will create a great deal of creosote and clog a chimney more quickly than dry hardwood fuel.

I think this is an example of a healthy flame, burning hot and not smoldering:
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Old 01-19-2008, 08:31 PM
 
Location: On the plateau, TN
13,660 posts, read 7,132,101 times
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Mike I agree about green and wet wood.....

Contrary to old wive’s tales Pine does NOT build up creosote in your chimney or stove pipe.

The following snippets can provide the real answers to that question:

Pine does have more “sap” content- but this is actually fuel- and it produces heat.

What causes creosote buildup? “The sticky, gum-like resins in pine firewood have given some people the impression that it produces more residue buildup, called creosote, than hardwood. Research has found this is not true.”

What REALLY causes creosote to build up?

Creosote is the condensation of unburned, flammable particulates present in the exhausting flue gas (smoke). The actual cause of creosote condensation, is the surface temperature of the flue in which the flue gas comes in contact. Like hot breath on a cold mirror, if the surface temperature of the flue is cool, it will cause the vaporized carbon particles in the flue gas (smoke) to solidify. This condensation is creosote build-up. If the wood you are using is rain logged, or green, the fire will tend to smolder. Wet wood causes the whole system to be cool, and inefficient. But, dry wood means a hot fire! A hot fire means a hot flue, and a hot flue means much less creosote.

Back in the early 1980’s, tests were conducted to discover which kind of wood created the most creosote in a regular “open” fireplace. The results were surprising. Contrary to popular opinion, the hardwood’s, like oak and madrone, created MORE creosote than the softwoods, like fir and pine.

The reason for this, is that if the softwoods are dry, they create a hotter, more intense fire. The draft created by the hotter fire moves the air up the chimney faster! Because it is moving faster, the flue gas does not have as much time to condense as creosote inside the chimney. Also, because the flue gas is hotter: it does not cool down to the condensation point as quickly. On the contrary, the dense hardwood’s tend to smolder more, so their flue gas temperature is cooler. Thus, more creosote is able to condense on the surface of the flue.

So, saying that “fir builds up more creosote than oak” just isn’t true! It is a misunderstanding to think that it’s the pitch in wood which causes creosote. It’s not the pitch that is the problem, it’s the water IN the pitch. Once the water in the wood has evaporated, that pitch becomes high octane fuel! When dry, softwoods burn extremely hot!
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Old 01-19-2008, 08:43 PM
Status: "Apple Pie!" (set 6 days ago)
 
Location: Cary, NC
19,560 posts, read 30,982,095 times
Reputation: 16566
Quote:
Originally Posted by Bones View Post
Mike I agree about green and wet wood.....

Contrary to old wive’s tales Pine does NOT build up creosote in your chimney or stove pipe.

The following snippets can provide the real answers to that question:

Pine does have more “sap” content- but this is actually fuel- and it produces heat.

What causes creosote buildup? “The sticky, gum-like resins in pine firewood have given some people the impression that it produces more residue buildup, called creosote, than hardwood. Research has found this is not true.”

What REALLY causes creosote to build up?

Creosote is the condensation of unburned, flammable particulates present in the exhausting flue gas (smoke). The actual cause of creosote condensation, is the surface temperature of the flue in which the flue gas comes in contact. Like hot breath on a cold mirror, if the surface temperature of the flue is cool, it will cause the vaporized carbon particles in the flue gas (smoke) to solidify. This condensation is creosote build-up. If the wood you are using is rain logged, or green, the fire will tend to smolder. Wet wood causes the whole system to be cool, and inefficient. But, dry wood means a hot fire! A hot fire means a hot flue, and a hot flue means much less creosote.

Back in the early 1980’s, tests were conducted to discover which kind of wood created the most creosote in a regular “open” fireplace. The results were surprising. Contrary to popular opinion, the hardwood’s, like oak and madrone, created MORE creosote than the softwoods, like fir and pine.

The reason for this, is that if the softwoods are dry, they create a hotter, more intense fire. The draft created by the hotter fire moves the air up the chimney faster! Because it is moving faster, the flue gas does not have as much time to condense as creosote inside the chimney. Also, because the flue gas is hotter: it does not cool down to the condensation point as quickly. On the contrary, the dense hardwood’s tend to smolder more, so their flue gas temperature is cooler. Thus, more creosote is able to condense on the surface of the flue.

So, saying that “fir builds up more creosote than oak” just isn’t true! It is a misunderstanding to think that it’s the pitch in wood which causes creosote. It’s not the pitch that is the problem, it’s the water IN the pitch. Once the water in the wood has evaporated, that pitch becomes high octane fuel! When dry, softwoods burn extremely hot!
Well, heck...
That makes sense.

And it is just a bad time of year to cut or buy fresh-cut wood.
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Old 01-19-2008, 09:45 PM
 
Location: On the plateau, TN
13,660 posts, read 7,132,101 times
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Glad you see the light... Some states only have fir trees to burn... Oak and other hardwoods should be cut and split at "least" a year in advance. I'm cutting and splitting right now for winter of 2009 and then in the spring for 2010 !!!!
Pine burns hot and fast when seasoned, so "do not" load up a fireplace or woodstove...
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Old 01-20-2008, 12:42 PM
 
8,286 posts, read 22,030,562 times
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If you're really trying to heat a place, then your open fireplace is a net heat loss ... even though it feels good to sit in front of the radiant heat of the fire.

Better to get an a fireplace enclosure that will allow you to block off the excess airflow heading up the chimney flue, and regulate the combustion airflow in combination with closing the damper as much as possible to retain heat in the firepit area.

Best is to get an insert that will have a controlled fire, with outside air for combustion and a smaller firebox which keeps the fire burning at a hot temperature, heating the surfaces of the woodstove which radiate heat into the house. You can find these in glass fronted units which allow the visual impact of the fire, or in sealed units ... either soapstone, steel, or iron models. You lose the beauty of the fire, but you gain the heat, with a lot more control, and have a net heat gain in the house instead of a pretty heat loss.

I have no difficulty starting and maintaining an excellent fire on the softwoods (elm, pine, fir) that are available in my area of the country with a Jotul, Waterford, or Blaze King closed woodstove. (I'm sure that there's many other brands, these are the ones I have). The small, hot fire readily burns all the sap and dries out the greenwood quickly.

The drawback to the softwoods is the lower energy content per lb of wood. On the softwoods, I have to add a bit of wood every 3-4 hours to keep the stove going well as you cannot "pack" the stove with wood and get the wood to form charcoal for a big bed of coals easily. On hardwood, when we can get it ... I can pack the stove and it will burn 8+ hours.
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Old 11-21-2008, 07:57 AM
 
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Bones, Can you tell me where you got that information on pine wood burning hotter/safer than hardwood? I would like to research it some more...
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Old 11-21-2008, 11:18 AM
 
3,020 posts, read 16,526,629 times
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Default You can burn green firewood......

It can be burnt if you use the right technology. Something called wood gasification which uses forced air to burn the wood at much higher temps. Everything is incinerated. Usually found in home boilers but it might be available in some stoves, maybe even a fireplace if they can design it in.

In general the burns are quicker and far hotter. The quality of wood is not that great of concern. Can be green or uncured.
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Old 11-21-2008, 12:26 PM
 
Location: Somewhere in northern Alabama
11,659 posts, read 26,758,670 times
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"If you're really trying to heat a place, then your open fireplace is a net heat loss ... even though it feels good to sit in front of the radiant heat of the fire."

Generally, this isn't true. Fireplaces are less efficient than wood burning stoves, but if they weren't effective, then those thousands and thousands of houses built prior to central heat would have been designed based on an idea that didn't work.

Can you burn green wood? Sure, but there are tricks to it. Aside from the difficulty of getting and keeping it lit, the reason not to do it is that some of the energy is wasted in evaporating the water in it into steam. That means you cut and use more wood than is needed if you allow the sun and time to dry out your firewood.

If your wood is short enough, you can build the fire in the center of a fireplace and place a green vertical log on either side, within the firebox. The heat will superheat the wood, but not turn it into a raging torch, because of the moisture constantly being driven off. When the fire dies down, you place the newly semi-dried logs on the main fire and add two new wet ones on the side. I do it all the time.

Gasification - all wood contains two primary flammable components - carbon and hydrogen. Carbon heavy gas tends to burn with a yellow flame, hydrogen with a blue or invisible flame. In gasification technology, the smoke is forced through the charcoal embers to create woodgas, or into a system where that smoke can be burned under more controlled conditions. Woodgas can fuel internal combustion engines, as it is primarily a weak carbon MONoxide, hydrogen, and methane mix, along with the natural nitrogen from the air. Woodgas is a far more efficient use of wood, and interestingly enough, charcoal woodgas producers have to ADD small amounts of water to create the dissociated hydrogen that forms the gas. (The oxygen combines more readily with the carbon, forming CO and CO2.)

Creosote - the common creosote deposits are dry and flakey because of the cycling of fires. Those can be quickly brushed out once or twice a season with a steel brush or even a rock-weighted sack of coarse cloth on a rope. The flakey creosote can create a hot quick chimney fire. To me, the more dangerous form of creosote is the slow thick buildup that occurs when fires are consistently underfed. It is harder to remove, and under the right combination of circumstances can create a nasty strong chimney fire. A professional chimney sweep should be hired if you suspect this type of buildup.

A word of warning about chimney fires - each is unique, and what works on stopping one can be counterproductive on another. Generally, the only time you'll have one is when you have a strong fire in the stove or fireplace. If you have a cast iron stove or old masonry chimney, you may be scrawed. Cast iron will crack and fall apart with thermal shock and masonry liners can spall and crack.

If you have a sheet steel stove or a fireplace, sometimes you can (from a distance) spray or toss a small amount of water onto the fire. The fire will flash vaporize the water into steam and lower the temperature of the gasses going up the chimney. If you have an airtight stove and use this technique you can actually smother a chimney fire with the steam. (You can also scald yourself to death from the steam flashback if you don't do it properly or get too close.) In a fireplace, the best you can hope for is keeping the temperature of the chimney fire below a temp where the flue will be damaged. Better to keep a DRY garden hose ready to hook up to a hose bibb or faucet and attack the fire from the outside. Speed is critical, and by the time the chimney fire is noticed, you might only have two or three minutes to prevent a major house fire.

I designed and built a gasifier-type vertical barrel stove back in the 1970s. It was a truly amazing stove that could get the temperature inside the house up to 100 degrees on a minus 30 degree night. Neighbors don't generally expect to see open doors and windows on the coldest nights of the year.
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Old 11-22-2008, 05:46 AM
 
Location: Eastern Kentucky
1,238 posts, read 1,705,052 times
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Actually, the fireplaces were not all that efficient. They were the only means of heating a home until wood stoves became available. They were the only means of cooking and keeping the family from freezing to death during the winter. I have been in homes which were heated with the old fireplaces and you got little heat when you moved away from the fireplace and almost none in the rooms which did not have a fire in the fireplace. They worked, just not well.
I was raised with a wood stove, and we always had a mixture of green and seasoned wood. The seasoned wood was used to get the fire started and burn down to a good bed of coals, then the green wood was added. The newer, airtight stoves may burn a bit differently.
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