Wood Moisture Content And Calorifi C Value; Storing And Drying Wood - HASE Toronto Mode D'emploi

19. Wood Moisture Content and Calorifi c Value
Rule of thumb: the more damp the wood, the lower the calorifi c value
The calorifi c value of the wood depends largely on the wood moisture content. The more
moisture the wood contains, the more energy expended to evaporate it during the combus-
tion phase; this energy is then lost. Thus, the more damp the wood, the lower its calorifi c
value. An example: freshly cut wood has a moisture content of approx. 50% and a calorifi c
value of around 2.3 kWh/kg; in contrast, wood which has been effi ciently air-dried has a
moisture content of approx. 15% and a calorifi c value of around 4.3 kWh/kg.
Accordingly, if you burn very moist wood, you will have about half the thermal output with
the same quantity of wood. Furthermore, burning moist wood results in substantial soot
build-up on the fi re box window. Moreover, when moist wood is burned, the resulting water
vapour can condense in the fl ue pipe or chimney. This can lead to a build up of shiny soot
on the chimney or chimney creosote. In addition, if the wood has a high moisture content,
the combustion temperature decreases, which prevents complete combustion of all the
wood components and causes considerable environmental pollution.
You can use a wood moisture meter to determine the residual moisture content of
your fi rewood.

20. Storing and Drying Wood

Wood needs time to dry. If stored properly, it will air-dry in approx. 2 to 3 years.
Saw, split and store the wood ready for use; this ensures rapid drying because
smaller pieces of wood dry better than larger, uncut logs.
Stack and store your wood logs in a ventilated and as sunny as possible location,
ideally facing south, and ensure that they are protected from rain.
Leave a hand's width between the individual piles of wood so that air can fl ow
between them and carry away any escaping moisture.
Do not cover your stacks of wood with plastic sheeting or tarpaulins; otherwise
the moisture cannot escape.
Do not stack fresh wood in a cellar or basement, since it will rot rather than dry
due to the lack of airfl ow.
Only store already dried wood in dry and well-ventilated cellar or basement
rooms.
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