You may think it’s a little late to start worrying about your
winter’s supply of firewood. But
there’s still time to “stack” up.
A number of people are selling firewood right now, both seasoned
and just-cut. In fact,
firewood prices seem a little lower than at this time last
year.
If you need to buy, keep in mind that when firewood is first
cut, it contains a good bit of
water. One fresh-cut cord of oak may have enough water to fill
five and a half 55-gallon
drums.
In a wood-burning stove or fireplace, that wood has to dry out
before it will burn. And boiling
off all that water steals a lot of heat away from the house.
That means the critical word when buying firewood is “seasoned.”
In general, the term means
the wood has dried to a level that will allow it to burn easily
and give up a high proportion of
its heat value.
Well-seasoned firewood will have dried to a point that less than
20 percent of its weight is
water. When the wood is first cut, water makes up 40 percent to
50 percent of its weight.
At the same moisture content, all wood produces about the same
amount of heat — pound for
pound. The difference is that some woods are heavier than
others.
Oak and hickory logs weigh more than the same size sweet gum or
pine logs. That means you
have to carry in and burn more pine or sweet gum logs to get the
same amount of heat.
Because it has more natural resins, pine actually yields
slightly more heat per pound than
hardwoods.
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.
The buildup on fireplace or wood heater walls, chimneys and flue
pipes seems more a result of
burning wood at relatively low temperatures.
When wood is heated, some of its chemical makeup is first
changed to a gas and later ignited
if the fire is hot enough. If the fire’s not hot enough, they
become part of the smoke. And if
they contact a surface cool enough, they’ll condense back to a
liquid or a solid there.
Over time, this layer of creosote becomes thick enough that a
hot fire will ignite it in place,
causing a chimney fire.
Filling a wood stove at night and closing the damper to reduce
airflow can keep a fire burning
all night with no more wood. But it also is likely to form
creosote.
Burning poorly seasoned wood favors creosote buildup, too,
because evaporating water cools
the burning process.
Burning small amounts of wood at high temperatures is one
solution to the problem, but doing
that by hand makes for busy and sleepless nights. The best
solution I know of is
automatic-feed wood-pellet stoves.
How can you tell if firewood is dry enough to burn well? It’s
not easy to tell. But there are
ways.
One is to split a fireplace log and look at the split surfaces.
Recently cut wood will have a
darker center with lighter, drier-looking wood near edges or
ends. Wet wood will be easier to
split than dry wood, too.
When firewood is very fresh, the bark will be tightly attached.
Bark on very dry logs usually
can be pulled off easily.
The real indication is weight. Because of the water in it,
unseasoned wood is heavier. Use a
bathroom scale to compare a fixed volume (such as a cardboard
boxful) of dry firewood with
wood of unknown moisture content. That will tell something about
the degree of seasoning.
