- 6th January 2022
- Posted by: Miranda Pont
- Category: Blog
As parts of the UK experience a cold snap this week, JBA’s arboricultural specialist Stephen Tester explores the use of wood burning stoves to heat homes. With advice on wood selection for modern stoves and how a recent change in the law in 2021 means that the sale of wet wood is now banned.
For some people, heating their homes includes the use of a fireplace or wood burner. Or maybe you are now looking at the rising cost of gas and considering if you should install a wood burner.
A greener lifestyle?
Wood burning releases a lot of CO2 yet heating with wood is often seen as an acceptable source of green energy. This is because with wood, if consumption and the potential carbon sequestration of trees is matched, then it can be considered a sustainable source of fuel unlike the fossil derived fuels.
However certain practices or ways of burning are more efficient at making use of the energy and carbon released and are less polluting than others. Most obviously burning wet or unseasoned wood, compared to seasoned/ dry wood, will be typically less efficient at giving off heat and will also release more air polluting particles and gases linked to reduced air quality.
Water content of wood and seasoning
Properly seasoned wood burns hotter, cleaner, and with less smoke. Following a recent change in law in 2021, the sale of wet wood is now banned. In practice, this means all firewood now sold should contain less than 20% moisture.
If you are buying from a supplier then you should request the wood meet these standards. It may even have been kiln dried which will often have less than 14% moisture content. If you’re seasoning your own firewood its worth knowing all timber varies in the amount of time it takes to season and so a small investment of £20-£25 for a wood moisture meter is highly recommended.
There is an old rule of thumb of ‘1 inch per year’ for seasoning wood so it is worth considering splitting the wood before stacking and storing your firewood, presenting a greater surface area exposed to air for faster drying.
Open hearth or wood burner?
Whilst the look, sound, smell and atmosphere of an open hearth is well loved in practice, an open hearth is often slow burning, inefficient and the heat radiated low. In contrast a modern wood burner can be efficient and often radiates the heat more quickly. In addition, there is some concern over the effects on health from an open hearth due to fine particle pollutants, and there is a potential risk of embers being spat forth from the open fire. Whilst old wood burners reduce the risk of embers being spat forth, they can similarly be as inefficient as an open hearth.
A modern wood burner is my recommendation. They come in various traditional or contemporary styles and often minimal conversion and maintenance requirements. Modern wood burners have been designed for optimal burning. They typically have a baffle plate which will ensure that any partially burnt gases and smoke is held, reheated and re-burnt, in what is considered a two stage burning process.
Which wood to burn?
With a couple of exceptions, pretty much any wood can be used. However species to species there are differences in their quality, below is a table showing some of common wood types and their suitability. If you want a full list please contact me direct for it.
|Apple||Needs to be well seasoned. Has a nice smell and burns well without sparking/spitting.||Good|
|Ash||Considered one of the best fire wood and readily available at the moment due to Ash Die Back disease. It has a low water content and can be burned green. Best when seasoned and will burn at a steady rate.||Great|
|Beech||Beech has a high water content so will only burn well when seasoned, generally splits well.||Good|
|Birch||Birch burns easily but also fast, so is best used for kindling or mixed in with slower burning wood such as Elm or Oak. Birch bark is also great as a firelighter.||Good -Great|
|H. Chestnut||Horse chestnut spits a lot and is considered a low quality firewood.||Poor- Okay|
|Leylandii||Spits excessively while it burns and can produce a lot of smoke and soot||Poor-Okay|
|Lime||Low quality firewood.||Okay|
|Oak||I think every one knows it is one of the best firewood when seasoned well! It provides lasting heat and burns at a slow rate.||Great|
|Pine||Pine burns well, with good heat. But due to the resin in the wood can spit and leave behind soot. Is also a good softwood for kindling.||Poor|
|Sycamore (Maple)||Considered a good firewood that burns well and also splits well.||Good|
Alternative sources of wood
If you decide to try and forage for free wood, most woodland owners or managers would not object to you picking up a few kindling sticks or pine cones whilst out on a walk. But to remove more would probably not be seen favorably by an owner, without their permission. From a legal perspective, you should always ask owners permission before taking.
An alternative source of wood may be waste wood in skips, or empty pallets. However owners permission will be required and you need to ensure that any wood is free of paint, preservatives or pesticides, as toxic chemical gasses are likely to be released when burnt – if in doubt, don’t burn it.
Want to know more?
Email Stephen Tester, arboriculture consultant, for more information or to discuss the arboricultural aspects of a project.