Firewood Facts

For the best heat output it’s important to always buy firewood that is as dry as possible and produced from a good quality hardwood species. You should always buy firewood by volume and not by the ‘load’ or by weight, as this will help you compare prices and ensure you receive the amount of logs that you ordered.

Any reputable firewood merchant will be pleased to tell you the moisture content, species and volume of the logs you are buying.

Log Moisture Content (MC)

The moisture content of wood has the biggest effect on the amount of heat that your firewood will produce. When trees are felled they typically have a water content of 50% or more. If you burn wet logs much of the energy locked up within the firewood will be used to dry the wood and produce steam, rather than heating your room.

Typically you will need to burn 3 logs with a moisture content of 50% to get the same heat output as burning 1 log with a moisture content of 20%.

Timber Species and Density

The density of wood also has an effect on the amount of energy contained within firewood and therefore the heat output produced. Hardwood species like ash and oak tend to grow more slowly than softwoods like pine and therefore have more energy contained within them for the same volume. This means that if you burn hardwoods instead of softwoods you will use less logs for the same heat output.

Typically you will need to burn 4 softwood logs to produce the same heat output as 3 hardwood logs, assuming the same moisture content.

Firewood Volume

We recommend that you always buy firewood by volume as this means that you can easily compare prices and ensure that you get exactly the quantity of logs that you ordered. If you do buy logs by the ‘load’ always ask what the volume of the delivery truck is and never buy firewood by weight as the wetter the wood the heavier it will be.

Typically a log with a moisture content of 50% will weigh 3 times as much as a log with a moisture content of 20%, assuming both have the same volume.

For more information on wood fuel and firewood you might like to visit the following websites - The Forestry Commission and The Biomass Energy Centre.