dannynelson77 said:This chart was just recently updated and all figures where downgraded a little. Would like to know the explaination as to why but I dont see it? For instance They used to have Red Oak and White Ash at about 24 MBTU. Now they are at about 22 MBTU. Also, they now have Honey Locust higher than Black Locust. It used to be vice versa. And its almost like they just rounded numbers with so many woods being exactly the same MBTUs now. They used to be more specific or exact with each type. Just makes me question the vailidity of the comparison. I know its just a guide but not sure why all the changes......
soupy1957 said:I'd be hard pressed to be able to call around and see if I could buy exclusively one preferred type of wood (say "Black Birch" for example, that has a very high BTU rating).
Battenkiller said:soupy1957 said:I'd be hard pressed to be able to call around and see if I could buy exclusively one preferred type of wood (say "Black Birch" for example, that has a very high BTU rating).
As far as the charts go, they are calculated by using the average density of each species when it is dry, then using the amount of chemical energy in a cord of wood at that density. Nobody is out there actually measuring the heat output from a wood stove using these woods. I feel that the charts are only a rough guide. How each wood burns in the stove is the final determinant of heat output.
For example, black birch is right about up there with black locust and shagbark hickory. Of the three, the black birch burns fastest, the hickory is second, and the locust burns for a very long time... at least in my stove. What that means is that the birch will put out more heat in a given time than will the locust, even though they all have close to the same BTUs in a cord. Sure, that also means I use more of it in a given time, but the extra heat output per hour can make the difference between a comfortable home and a chilly one.
This chart is probably maintained by a 18 yr old secretary that doesn't know a wood fire from a gas fire. Or the person that maintains it adjusts it for his own (financial) purposes. Man, am I cynical or what?dannynelson77 said:This chart was just recently updated and all figures where downgraded a little. Would like to know the explaination as to why but I dont see it? For instance They used to have Red Oak and White Ash at about 24 MBTU. Now they are at about 22 MBTU. Also, they now have Honey Locust higher than Black Locust. It used to be vice versa. And its almost like they just rounded numbers with so many woods being exactly the same MBTUs now. They used to be more specific or exact with each type. Just makes me question the vailidity of the comparison. I know its just a guide but not sure why all the changes......
soupy1957 said:Unfortunately, since I don't cut down my own trees, or cut up fallen trees, I'm at the mercy of the guy or gal I choose to buy from. Typically, a wood load will have a mix to it. Some very desirable woods will be in it, and then again, perhaps not so much so. I'd be hard pressed to be able to call around and see if I could buy exclusively one preferred type of wood (say "Black Birch" for example, that has a very high BTU rating).
Would I LIKE to get the most BTU's out of my wood that I'm burning? Sure............
-Soupy1957
Energy in WoodIt is also useful to note how these concepts apply to un-seasoned (green) wood fuel. If only seasoned a short time, 50% moisture is a realistic figure. Then a two-pound piece has one pound of wood fibers (worth 8660 Btu). There will be 1.54 pounds of water to vaporize and heat up (taking away 2200 Btu). The two-pound piece has a net available energy content of 6460 Btu or 3230 Btu/pound. This is only HALF of the available energy present when burning seasoned wood. Green wood consumes the bulk of its energy just to keep itself going, and is obviously subject to easily going out.
A freshly cut tree has even higher moisture content, often above 60%. Similar calculations show that this fresh wood has only 2000 Btu/pound of energy available. This explains why it is so difficult to burn freshly cut trees.
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