Wood is an ideal fuel which is in plentiful supply and is renewable. It is important that the wood is dry and well seasoned. Burning wet or unseasoned wood is less efficient because much of the heat produced as it burns will be required to drive off the moisture contained within it as steam.
Water vapour combines with other gases and particles going up the chimney and unless the chimney is kept warm the condensation forms a creosote-like substance which hardens to form tar on the surface of chimney liners and may seep into brickwork in an unlined chimney. Wet logs cause the chimney to cool and so condensation occurs and a residue is formed. The chimney may become completely blocked with this residue allowing harmful fumes to escape into the dwelling. The volatile residue can ignite causing a dangerous chimney fire.
You would need to burn around three times as many unseasoned logs to achieve the same heat output as well seasoned or kiln dried logs.
Wood fuel is virtually carbon neutral. It absorbs as much carbon dioxide in its growth as it releases when it is burnt. For this reason, the installation of wood fuel appliances is currently treated more favourably in the building regulations.
Smoke Control Areas
The Clean Air Act allows local authorities to designate smoke control areas which place legal restrictions on combustion and the use of certain appliances and fuels. If you wish to burn any type of wood fuel and you live in a smoke control area, you may only do so if you burn wood on an “exempt” appliance.
A list of appliances which are currently exempted by DEFRA under the Clean Air Act may be found here.
To find out if you are in a smoke control area see your local authority website.