Freshly cut wood may contain as much as 100 percent moisture, which means the water in the wood weighs more than the wood. Building a fire from wet wood, also called green wood, is less efficient and less safe than using properly dried or “seasoned” firewood. Firewood should have 20 percent moisture or less.
Burning wet wood is less efficient than burning dry wood because so much energy is lost in warming water to steam. Vaporizing a pound of water wastes about 1,200 British thermal unit, or BTU, a measure of heat. In contrast, a pound of firewood that contains 20 percent moisture provides about 7,000 BTU of heat.
Burning wet wood in a fireplace may also be dangerous to your health. Wet wood produces more smoke than dry wood, which releases more pollutants and small particles into the air. Burning wet wood in a fireplace can also cause creosote buildup in your chimney, which may create a fire hazard. This occurs because wet wood produces less heat, which allows creosote to build up on the fireplace flue.
If you’re not sure whether your firewood is dry, check the ends of the pieces of wood. Small splits in the wood mean the wood is probably dry, while a smooth texture indicates a higher moisture content. You can also knock two pieces of wood together. Wet wood creates a quiet noise, while dry wood makes a louder clinking sound. In addition, you can use a wood moisture meter to check the moisture content of firewood.
Season freshly cut firewood by storing it in a covered outside location off the ground for at least six months. Dense hardwoods may require a year or more to season effectively. Place the wettest wood in the back of your storage area or on the bottom of the firewood stack to ensure you use seasoned wood first. If you purchase firewood, verify that it has been dried in a covered location for at least six months.
Woodsure, the UK’s woodfuel accreditation scheme is launching a new initiative for wood log suppliers. The Ready to Burn certification mark is available to wood log suppliers who can demonstrate to Woodsure their logs have a moisture content below 20%. The scheme is focusing on pre-packed woodfuel.
Recent publicity around poor air quality and linking to the increased use of wood stoves has questioned whether casual consumers buying smaller retail bags of woodfuel realise the wood they are burning may not be suitable for immediate use. Its use in wet form would contribute significantly to particulate emissions whilst burning dry wood has significant and demonstrable benefits in greatly reduced emissions. Modern stoves are designed to burn dry wood.
Industry representatives, including large producers of pre-packed woodfuel have committed to a scheme that will clearly identify the wood that is ready to burn at the point of sale. It will also raise awareness for wood fuel consumers to only burn low moisture, ready to burn firewood.
About the scheme
The ‘Ready to Burn’ initiative is for wood log producers, having a distinct certification category for dry firewood logs where they are able to demonstrate through audit and fuel testing that woodfuel they sell as ‘Ready to Burn’ is:
Labelled as ‘Ready to Burn’
Is less than 20% moisture content
There is point of sale information, labelling and support
Where appropriate provides retailers with information on how to effectively store and keep the firewood in good condition
Making this dry fuel available to consumers in a way that they can recognise it is ready to burn and differentiate it from wet wood, will significantly increase the sale of dry wood whilst at the same time educating consumers on the benefits.
The principle of the Woodsure scheme is that raw materials, the collection of trees and forestry thinning or post timber processing is legally sourced, processed to achieve size and moisture characteristics and made available to the end consumer with clear identification.
The scheme has the backing of HETAS, the Stove Industry Alliance and producers of pre-packed woodfuel. It is proposed a governance body will be set up to oversee the scheme.