Warm Advice Straight From The Hearth:
A fireplace means a roaring fire with bright,
licking flames to some people. For others, it's
the muted crackle and soft warmth from a bed of
glowing embers. While small "warming" fires are
significantly more energy-efficient than the
larger variety, the home fires that burn in your
fireplace can be either big and bold or small
and mellow, depending on how you build them.
The size and position of logs in a fireplace,
plus the placement of embers and ashes, are key
factors in determining the character of a fire
as well as the amount of heat it delivers.
Large, rapidly burning fires produce heat
quickly and in quantity, but only make use of a
small percentage of the total heat available
from the wood. Far better in terms of energy use
and conservation are smaller, more controlled
fires that produce less heat, but do so longer
and deliver a much larger percentage of
available heat.
The difference in the warmth or energy delivered
by the two types of fires is the amount of heat
that escapes up the chimney. The bulk of the
energy from larger, quickly burning fires goes
up the chimney via a wide-open damper plate.
These fires require a lot of air for combustion
and draw it from the heated air within the
house; this warm air is replaced by drawing
cold, outside air into the house.
Unless the thermostat is turned down, the
furnace will operate more frequently to
compensate for the influx of cold air. In
addition, as the house air moves into the
fireplace, it will produce uncomfortable drafts.
And hot, fast fires usually use larger logs than
small fires and require frequent trips to the
wood pile, as well. (The large flames are pretty
but are a sign of very inefficient burning.)
Small "warming" fires consume logs more slowly,
require less air (and therefore, a smaller
damper opening) and burn in such a way that most
of the available heat is radiated into a room.
(Small fires rely on glowing coals and often
will display little or no flame.)
Most people build fires using three logs two
equally sized ones on a grate several inches
apart, plus a third one set atop the first two.
Once the fire catches, the logs radiate heat
between each other until the facing surfaces the
tops of the lower logs and the underside of the
top one become glowing coals. Few of the radiant
energy waves from these surfaces will exit the
fireplace to heat objects or you. The air supply
from underneath tends to carry off most of the
energy in a hot air current straight past the
open damper and up the chimney. (Large licking
flames are evidence of this energy waste.)
By strategic log placement and intelligent use
of ashes to block air routes under the fire,
however, you can obtain a more effective
radiating coal bed. Before building your fire,
move or place ashes under the grate so that logs
placed on it will just bed in the ashes. Put a
six to ten-inch diameter log on the rear of the
grate and a four to six-inch one on the front.
Place crumbled newsprint, then kindling wood
between the two logs. Light the paper and get
the kindling going. Place a single layer of
two-inch logs over the flaming kindling. Add
logs in increasing sizes until you reach the
four-inch ones.
As the smaller logs between the larger rear
"reflecting" log and the smaller front
"retaining" log are consumed, their coals will
form a bed. Feed this bed to maintain a pocket
of red coals and a single layer of burning wood.
As the rear and front logs are consumed, roll
them into the bed and replace them.
This type of slow, small fire will have a
relatively large surface of heat-radiating
coals; the rear log will reflect misdirected
energy waves back into the room. Also, a slow
fire will consume very little household air and
can be operated with the damper only slightly
open; additionally, individual pieces of wood
will take a much longer time to be consumed and,
as the coal bed deepens, less and less fuel will
be needed. (A smoldering fire can be kept alive
all night by covering the coals with ashes a
procedure called banking. However, never bank
coals or leave a fire unattended unless a glass
screen is tightly closed over the fireplace
opening.)
Finally, smaller fires can be burned in
fireplaces that tend to smoke with larger fires;
they also produce less ash and leave a cleaner
flue. If you feel you can't get through the
winter without the charm and excitement
generated by crackling and flaming logs,
remember that you can start big then cut back on
additional fuel to reduce the size of the fire.
An equally effective and far more efficient way
to add flair to your fire, however, is to place
a few pieces of fruitwood on the bed cherry and
apple give off wonderful aromas.
A traditionally lined chimney has a terra cotta
flue lining and considerably fewer mortar joints
exposed to direct heat; consequently, it is
considered to be significantly safer. (The
exceptions are unlined chimneys that are three
courses of brick thick; these are safe to
operate without a liner, presuming the mortar is
sound.)
To determine if your chimney is lined or to
check the condition of an existing liner open
the damper (if there is one) and look up the
chimney. With the aid of a strong flashlight,
you should see where the bricks angle inward
above the damper plate. The top of this area is
where the bottom of the lining would start look
for a smooth lip and the absence of brick mortar
joints above.