Wood is an excellent source of renewable heat energy. But performance varies depending on the type of wood you burn.
Here we look at how to gain maximum efficiency from your wood burning stove by using the correct type of wood fuel.
Choose hardwoods rather than softwoods
As a general rule, hardwood burns better than softwood in wood burning stoves. This is because hardwoods are slow-growing deciduous trees and their logs have a greater density.
Hardwood is heavier than softwood and therefore will give you up to 50% more heat output and a longer burn time. This means you don’t have to fill the stove up as often. Ash, Birch, Beech, Oak and Elm are all ideal for wood burning stoves.
Use dry, seasoned wood
Wet wood is less efficient and tends to be difficult to light, with shorter burn times. It can also produce smoky fires. You’ll notice the difference when you burn decent wood as this often doesn’t generate much smoke at all.
Wood should be seasoned outdoors for between 18 to 24 months. To do this, keep logs stacked off the ground with space between them to allow for air movement and cover to keep rain and snow off.
Fully seasoned wood logs should have a moisture content of less than 20% - good indicators of this are when the bark starts to peel away, and cracks and splits occur around the outside of the wood.
It’s worth the effort to dry wood, as seasoned logs will give you 50% more heat output than unseasoned ones.
Woods to avoid
Plywood, MDF, chipboard and any other manufactured or finished wood should not be used in wood burning stoves due to the chemical adhesives and varnish content used in their construction. Not only will this type of wood leave harmful residues inside the stove and flue system, it could also give off noxious fumes.
Also, check your wood has not been treated with any paint or preservatives. Treated wood can produce harmful gas emissions and it could also damage your stove’s flue linings and chimney.
Briquettes are highly efficient
Briquettes are produced from crushing recycled wood, paper or peat together. They burn efficiently as they have a low moisture content – sometimes 10% or less. The burning qualities of briquettes are different to that of wood, as briquettes can produce more heat, so you may need to adjust the settings on your stove.
Briquettes are popular as they are so convenient. Their density means less storage space is required, and they’re simple and clean to handle. You can buy them in easy to carry retail packs.
Wood pellets for specialised stoves
If you have a specialised wood-pellet stove, you can usually buy wood pellets that are typically made from the same raw materials as briquettes. However, wood pellets are much smaller than briquettes, making them easy to store.
Wood pellets also generally have around 10% moisture content, which means they are highly efficient when it comes to heat output.
Choosing the right wood fuel
Always check the instructions of your wood burning stove as it will advise the correct fuel to use in your size and type of appliance.
For more information on this subject, HETAS has produced this useful guide:
If you’d like advice on any aspect of wood burner or multi-fuel stoves, then contact Peter, a HETAS registered engineer, on 07749 863650.