There are two significant factors that affect the energy you get from wood. The first is factor is the amount of water present in the firewood, its moisture content. The other is the density of the wood; hard wood gives a longer and more consistent burn, however, most softwoods are good in itself as a firewood.
There are many myths about firewood and what you can burn. The most regular one that pops its head up is that Ash wood does not need to be dry. Although Ash wood does have a lower moisture content (the amount of water in the wood) when felled it still is WET! There is approximately 35% water content in Ash as opposed to maybe 50% for Oak. Therefore, even though Ash wood may well burn, it will not burn very efficiently and in fact takes large amount of heat just to dry it out during the burning process.
You may also run the risk of producing large amounts of condensates (tarring) in your flue, which can be a costly thing to repair. So, wood should always be as dry as possible before burning. Burning dry wood will result in a number of benefits to the woodstove owner:
- Less tarring of the flue
- Reduces risk of chimney fires
- Better efficient burn – warmer house
- More cost effective – If the wood is wet then a considerable amount of heat is lost boiling off the moisture reducing the heat output to the room
- Using wet wood means you have to burn larger amounts of wood for your heating requirements
What is seasoned wood?
The recognised standard for seasoned firewood is moisture content at 25% or below. Ideally, we would recommend 20% moisture content or below. There are many firewood suppliers who may be able to supply wood that is seasoned but this can be difficult to measure by the end user (i.e. you). Please see our page on buying wood.
A good measure of whether firewood is seasoned is to ask – was the wood felled, split and correctly store at least a year ago.
Doing it yourself
Correctly storing your wood is key to getting good quality dry firewood. A purpose made woodstore should be used for this. Essentially, it is covered from the rain but allows free flowing air to enable the drying process. A good way to visually check is to look for cracking at the end of log that radiates outward. The only way to really know though is to use a moisture meter.
Seasoning firewood checklist:
- Logs are split to around 100-120mm (4-4.75 inch) diameter – Splitting wood is easy when green and this also helps the drying process – this diameter is also the best size for the most efficient burn
- Position the woodstore in sunny but dry position – South to SE is probably best, South West worst due to prevailing weather (rain) and Northwards also poor due as not sunny
- Woodstore should be raised off the ground
- Slated sides with gaps are acceptable but a closed shed will not work (it will not dry properly and can become mouldy which draws more moisture in and becomes poor wood for burning)
See the link to our list of Woodstore suppliers locally found.
Forestry Commission - Woodfuel as Fuel guide
Forestry Commission - Wood as Fuel Technical Supplement on types of wood and calorific values each type.
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