Firewood Moisture Content & Burning Advice
Practical guidance on moisture content, burning performance and getting the best from your firewood.
Why firewood moisture content matters
Properly seasoned firewood should have a moisture content of 20% or less. Drier wood lights more easily, burns more efficiently and produces more useful heat, rather than using energy to evaporate water held within the logs. Burning wet wood can also create more smoke and increase deposits on stove glass and inside the chimney or flue.
We select three or four larger logs from the middle of each bag, split them open and test the freshly exposed core with a pin moisture meter. We are also happy to demonstrate the test in front of our customers.
Under 20% moisture content
Our firewood is tested to be under 20% moisture content so you get the true value of the energy it holds.
Calorific value and moisture content
The below shows how the calorific value of firewood increases as the moisture content decreases.
Source: Wood Fuels Handbook
Reference values for biomass fuels
The following table is taken from the Wood Fuels Handbook and details the calorific value, ash content and ash-melting point of various biomass fuels.
| Calorific Value MJ/Kg | Ash (wt% d.b.) | Ash melting point (°C) | |
|---|---|---|---|
| Typical values for virgin wood materials Coniferous wood | 19.2 (18.8-19.8) | 0.3 (0.2-0.5) | |
| Typical values for virgin wood materials Deciduous wood | 19.0 (18.5-19.2) | 0.3 (0.2-0.5) | |
| Typical values for virgin bark materials | 20 (19-21) | 4-5 (2-10) | |
| Typical values for virgin wood materials Logging residues | 19-20 | 1.5-2 | |
| Typical values for virgin wood materials Short rotation coppice (SRC) (Willow & Poplar) | 18.6-19.2 | 2 | |
| Spruce (with bark) | 18.8 | 0.6 | 1426 |
| Beech (with bark) | 18.4 | 0.5 | 1340 |
| Poplar (SRC) | 18.5 | 1.8 | 1335 |
| Willow (SRC) | 18.4 | 2.0 | 1283 |
| Bark (coniferous trees) | 19.2 | 3.8 | 1440 |
| Calorific value, ash content and ash-melting point of various biomass fuels. Source: Wood Fuels Handbook, Biomass Trade Centres, April 2009 | |||
Storing your logs
Store logs in a well ventilated place, off the ground. Good airflow is essential to keep moisture low.
Burning efficiently
Use dry kindling to get your fire going quickly and keep air vents open. A hot, lively fire is more efficient and produces less smoke and deposits.
Need advice?
We’re always happy to help if you have any questions about your firewood, storage or burning. Just get in touch. We’ll point you in the right direction.