Best Burning Wood
It doesn't matter what kind of wood you burn, but it does matter if it has been seasoned properly. Hardwoods, especially oak, must be season for over a year. Properly seasoned wood produces the most heat and produces the least creosote. Firewood that hasn't been split for over a year isn't going to burn well.
If you have a problem starting your fire or keeping the fire going you are probably using this year's wood. That means it has not been seasoned. Unseasoned or green wood is extremely frustrating and disappointing. Unseasoned wood is hard to light, it will keep going out, and it will smolder. It will not put out heat. It is the moisture in the wood which causes creosote to build up at an accelerated rate. One fresh-cut cord of oak may contain enough water to nearly fill six (6) 55 gallon drums. The moisture content in the wood determines how much heat the fire puts out, and how much creosote will build up in your chimney.
Seasoned wood look dark, or gray when compared to green wood. If you split a piece of seasoned wood it is white on the inside. It is brittle. It has cracks running through each piece and a lot of little cracks on the inner rings. Unseasoned wood has a wet, fresh looking center, with lighter wood near the edges or ends which have been exposed since cutting. When firewood is very fresh, the bark will be tightly attached.
Creosote is the condensation of the unburned, flammable particulate 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 your breath on a cold mirror, 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 your wood is wet or green, the fire will smolder. Wet wood causes the whole system to be cool and inefficient. Dry wood means a hot fire. A hot fire means a hot flue, and a hot flue means much less creosote.
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 hardwoods, 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 tends 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!
When buying firewood make certain it is well seasoned. The best way to get seasoned wood is to cut this year's wood for next year. A moisture tester may be a good investment. Once wood gets over 4- years old, it does start to deteriorate, so the best wood is 2-3 years seasoned. Most wood for sale is “this year's” wood. If you get serious about wood burning, you must always think one full year ahead. Hardwoods are the choice of the serious fire burner. You may pay $300 for a cord of oak and only $250 for a cord of fir. Because the oak is denser, it weighs much more than the fir. You actually get more for your money with hardwood. Because hardwoods are denser, they provide more available fuel in the same space. The fuel available in hardwood enables stoves or inserts to sustain high temperatures for significantly longer periods. Also, unless the stove is shut down tight, hardwoods may keep a hot live coal bed for days. Airtight stoves or inserts perform best with dry hardwoods.