Wood Fuel

Logs (download ‘Guide_to_Wood_and_Multifuel‘)
The most common form of wood fuel at the moment is logs. These will usually come from local sources and can be brought from a variety of outlets – e.g. coal merchants, farmers, tree surgeons. It is important the logs are dry and well seasoned. Burning wet or unseasoned wood is less efficient and can cause harmful build up of deposits in the chimney over a very short time. Thick coatings of creosote or resinous material can cause chimney fires, or prevent the chimney functioning properly. This can allow harmful fumes to escape into the dwelling.

Efficient burning is achieved by setting the appliance to burn fast after stoking. This will ensure that all the gases are fully burned. Only set to slow burn when all wood has been reduced to charcoal and ash. Newly added wood set to burn slowly creates smoke and creosote in the chimney. The stove should not be banked up with logs for overnight burning. A bright fire which has turned the wood into charcoal should be left with the day’s ash, no secondary air and minimal primary air.

If you buy logs which have not been seasoned, you should store them under cover but open to allow free air circulation for at least a year. Some logs may take 3 to 4 years to fully season. Bring the fuel into the house a few days before you want to use it to get it as dry as possible. Wood from different trees has different heat values The table below provides a useful comparison. Wood fuel has typically less than half the calorific value of coal and smokeless fuel, so you must be prepared to use a greater volume of wood to heat your home or room, unless you use both wood and mineral solid fuel.

Under the Weights and Measures Act, coal and smokeless fuel have to be sold in defined weights, which makes it easy for you to compare the cost between suppliers. Unless there is a local statutory instrument in force, there will be no such statutory weight for deliveries of wood. The logs and wood are usually sold in “nets” or by lorry load, so take care to check the amount you can expect to get for your money. Fresh felled wood weights about one tonne per solid cubic metre but will lose up to half its weight when it becomes fully air dried, so find out for how long the wood has been seasoned before delivery.

If you burn wood, you should have your chimney swept at least twice a year. Do not burn any painted or treated wood. Treated or painted wood will emit chemicals which are potentially damaging to health and the environment. This also applies to MDF and chipboard.