R
7100FP EPA Woodburning Fireplace
Moisture content
Regardless of which species of wood you burn, the single most important factor that affects the way your fireplace operates is the amount of moisture in the wood. The majority of the problems fireplace owners experience are caused by trying to burn wet, unseasoned wood. Freshly cut wood can be as much water as it is wood, having a moisture content of around 50%. Imagine a wooden bucket that weighs about 8 pounds. Fill it with a gallon of water, put it in the firebox and try to burn it. This sounds ridiculous but that is exactly what you are doing if you burn unseasoned wood. Dead wood lying on the forest floor should be considered wet, and requires full seasoning time. Standing dead wood can be considered to be about
The problems with burning wet, unseasoned wood are two fold. First, you will receive less heat output from wet wood because it requires energy in the form of heat to evaporate the water trapped inside. This is wasted energy that should be used for heating your home. Secondly, this moisture evaporates in the form of steam which has a cooling effect in your firebox and chimney system. When combined with tar and other organic vapors from burn- ing wood it will form creosote which condenses in the relatively cool firebox and chimney. See the maintenance section of this manual for more information regarding creosote formation and need for removal.
Even dry wood contains at least 15% moisture by weight, and should be burned hot enough to keep the chimney hot for as long as it takes to dry the wood out - about one hour. To tell if wood is dry enough to burn, check the ends of the logs. If there are cracks radiating in all directions from the center, it is dry. If your wood sizzles in the fire, even though the surface is dry, it may not be fully cured.
Seasoning
Seasoned firewood is nothing more than wood that is cut to size, split and air dried to a moisture content of around 20%. The time it takes to season wood varies from around nine months for soft woods to as long as eighteen months for hardwoods. The key to seasoning wood is to be sure it has been split, exposing the wet interior and increasing the surface area of each piece. A tree that was cut down a year ago and not split is likely to have almost as high a moisture content now as it did when it was cut.
WARNING
Fire Risk
•Do NOT burn wet or green wood.
•Store wood in dry location.
•Stack wood so both ends are exposed to air.
Wet, unseasoned wood can cause accumulation of creosote.
Storing Wood
Splitting wood before it is stored reduces drying time. The following guideline will ensure properly seasoned wood:
a.Stack the wood to allow air to circulate freely around and through the woodpile.
b.Elevate the woodpile off the ground to allow air cir- culation underneath.
c.The smaller the pieces, the faster the drying process. Any piece over 6 in. (152 mm) in diameter should be split.
d.Wood should be stacked so that both ends of each piece are exposed to air, since more drying occurs through the cut ends than the sides. This is true even with wood that has been split.
e.Store wood under cover, such as in a shed, or cov- ered with a tarp, plastic, tar paper, sheets of scrap plywood, etc., as uncovered wood can absorb water from rain or snow, delaying the seasoning process. Avoid covering the sides and ends completely. Doing so may trap moisture from the ground and impede air circulation.
WARNING
Fire Risk
Do NOT store wood:
•Closer than required clearances to combustibles to fireplace.
•Within space required for loading or ash removal.
September 7, 2007 | Page 47 |
