Burn Only Dry,
Seasoned Firewood
Freshly cut wood contains up to 80% moisture,
and must be "seasoned" (dried to 20-25% moisture content)
before burning. Wood containing more than 25% moisture is "wet"
or "green", and should never be burned in a fireplace
or woodstove. If exposed to rain, a fallen tree will wet-rot before
it ever dries enough to be used for fuel. To properly season firewood,
cut it into stove-sized pieces and stack it so air can circulate
and carry away the moisture as it evaporates through both ends
of each piece. The woodpile must be sheltered to prevent rainwater
from being re-absorbed, which reverses the drying process: firewood
that is exposed to rain will rapidly become just as wet as it
was when freshly cut. Wood must be cut into pieces and stacked
out of the rain for at least 6-9 months to season properly. If
no seasoned wood can be found, high-density compressed sawdust
logs make an excellent substitute. Avoid burning mill ends in
woodstoves, as the exhaust from even "untreated" mill
ends has shown itself to be tremendously corrosive to metal.
Burn The Wood
Gases
Most of the moisture content remaining in
seasoned firewood consists of wood resins. As wood heats up in
the fire chamber, these resins emit combustible gases which, when
ignited in the secondary burn chamber, can account for as much
as half the heat output of the fire. When green or wet firewood
is burned, the extra water content turns to steam and mixes with
the wood gases, preventing them from igniting and releasing their
heat value. When the draft control is set too low and the fire
smolders, the wood gases won't ignite in the resulting oxygen-starved
environment, even if the firewood is properly seasoned. When the
wood gases aren't burned in the secondary burn chamber, they escape
up the chimney, taking their heat value with them and creating
heavy creosote formation.
Don't Let Creosote
Build Up In The Chimney
Creosote is a highly combustible substance
which condenses in liquid form as wood exhaust cools in the chimney,
and then solidifies as it dries. If ignited, creosote can burn
for days at temperatures exceeding 2,000 degrees, which is hot
enough to destroy the chimney and ignite surrounding combustibles.
Creosote is very caustic; if allowed to accumulate, it will significantly
shorten the lifetime of the stovepipe and chimney. A seasoned-wood
fire that is given enough oxygen for proper combustion will reduce
creosote formation in two ways, by consuming more of the wood
gases while at the same time sending more heat up the chimney
to reduce flue gas cooling.
Practice Proper
Chimney Maintenance
Creosote should be removed from the chimney
before buildup in the flue exceeds 1/4" thickness. Chimneys
which vent properly operated woodstoves generally require cleaning
once per year. If green or wet wood is burned, or if the fire
is allowed to smolder, the chimney will require cleaning much
more often, and should be inspected frequently. Creosote sticks
like glue, and must be removed with a tight-fitting steel brush.
Rattling tire chains down the chimney or pulling a bag of straw
through the flue won't remove creosote, and neither will a chimney
fire. Chimney fires burn away the resinous portion of the creosote,
but the sooty husk remains: if this husk isn't removed after a
chimney fire, smoke will filter through it, rapidly re-depositing
fresh liquid resin. In a very short time, the chimney will be
as bad as it was before the fire.
Follow These
Woodburning Tips
If steam bubbles and hisses out of the end
grain as the firewood heats up on the fire, the wood is wet or
green, and needs to be seasoned longer before burning.
If a wood supplier advertises his wood as
"seasoned", or claims that it has been "down"
for a year or two or ten, be skeptical. Ask if the wood has been
cut into pieces and stacked out of the rain for at least 9 months.
If it hasn't, it isn't ready to burn.
Shelter the woodpile from the rain, but don't
cover it completely with plastic tarps or store it in an enclosed
shed or garage; air circulation is necessary to ensure proper
seasoning.
Never burn garbage, mill ends, or individually
wrapped compressed sawdust logs in a woodstove. These contain
chemicals which, when burned, are highly corrosive to metal.
Unless the stove is EPA approved, never try
to make a load of fuel burn longer than 6-8 hours. EPA approved
appliances have built-in safeguards to prevent smoldering, but
many older airtight can be adjusted to smolder along for extended
periods, resulting in heavy creosote deposits.
Operate woodstoves with their draft control
wide open for 20-30 minutes each time firewood is added, or until
the fresh load is totally engulfed in flames. This will send heat
up the flue to help solidify the liquid creosote deposited by
the previous load, while kindling the wood to start gasification
of the resins for efficient burning.
NEVER try to clean a chimney by deliberately
starting a chimney fire. Have the chimney professionally cleaned
and inspected at least once per year.
If a chimney fire occurs, close the draft
control on the stove completely to quench the supply of oxygen,
and call the fire department immediately. Then, make sure the
chimney is thoroughly cleaned as soon as possible.