Damp wood damages
your fireplace and
reduces efficiency!
2.3 BUYING FIREWOOD
Where can I get my firewood?
BUYING READY-TO-BURN FIRE-
WOOD
Regenerated ready-to-burn firewood
can be purchased from dealers:
• stove-ready, stored for at least two
years
• predried, stored for one year
• fresh from the forest
Every dealer has a wood moisture me-
ter that they use to test the wood they
buy. The ideal residual moisture is 12–
15% and should be no higher!
TREATING FIREWOOD YOURSELF
Unseasoned wood can be purchased
from the forestry office, owners of
woodland, or the community:
• trunks lying in the forest
• seasoned trunks by the wayside
Whether you have cut your own wood
or bought it, the important thing is:
the wood should be dried for at least
two years before it is burned!
2.4 DRYING AND STORING
WOOD
DRYING
The water content of firewood has a
great effect on its burning properties.
Your wood should be as dry as possi-
ble. Only then can it give off much heat
and burn without polluting the envi-
ronment. Freshly cut wood can contain
between 45 and 60% moisture depen-
ding on the season and type. After
the optimal drying this water content
drops to below 15%. Depending on the
wood type this can take about two ye-
ars, and even longer for some kinds.
STORAGE
If
firewood is to dry thoroughly, it must
be cut into small pieces.
Check this yourself: the circumference
should be max 20–25 cm. Store the
wood out of doors, protect it from rain
and snow, and make sure it is well ven-
tilated.
2.5 WOOD TYPES AND
CALORIFIC VALUE
The calorific value describes the heat
energy released when one kilogram
of fuel is burned under specific condi-
tions.
The calorific value is based on the vo-
lume specified in stacked or solid cu-
bic metres.
The various wood types have various
calorific values:
!
What you must not
burn: refuse, wet wood,
briquettes!
!
A TONWERK STORAGE HEATING
STOVE CAN BE FIRED WITH ALL OF
THE ABOVE WOOD TYPES.
The values are based on 15% residual wood moisture!
The many oils and
resins in larchwood also
provide for an acoustic
fireworks!
i
Loose cubic metre (lcm):
The loose
cubic metre is a measure for chopped
firewood that is loosely packaged for
trade and transport. One loose cubic
metre is 0.7 steres or about 0.5 solid
cubic metres.
NOTE THE SPECIFIED UNIT OF
MEASUREMENT WHEN ORDERING!
Solid cubic metre (scm):
As its name
suggests, the solid cubic meter corre-
sponds to one cubic metre of solid as
opposed to stacked wood.
Stacked cubic metre (stcm) or stere
(st):
A stacked cubic metre or stere
corresponds to one cubic metre of sta-
cked wood including the gaps between
layers. One stere equals 0.7 solid cu-
bic metres.
2.6 UNITS OF MEASUREMENT FOR WOOD
TREE
CALORIFIC VALUE
Hardwoods
beech, oak, locust 2100 kWh/stcm
birch
1900 kWh/stcm
sycamore
1900 kWh/stcm
Softwoods
Douglas fir, pine
1700 kWh/stcm
larch
1700 kWh/stcm
spruce, fir
1500 kWh/stcm
1 solid cubic metre – 1 scm
1 stacked cubic metre/
stere – 1 stcm
1 loose cubic
metre – 1 lcm
1 fm
0.7fm
0.5 fm
