When choosing firewood there are two significant factors to consider which have an effect on the calorific value (CV) or the amount of available heat per unit (volume) of fuel, these are moisture and wood density.
Any water in wood has to boil away, this process uses energy and reduces the heat produced by the log, so dry logs burn more efficiently, with a higher heat.
Logs that have a high moisture content will result in a fire that smoulders and creates a lot of tar and smoke, these tars can be corrosive and potentially damage the lining of the flue, wet logs can also blacken glass in stoves.
Avoid using wood that’s known as wet or green which contains high levels of moisture. It is better to used seasoned wood or kiln dried wood, this is timber that has been dried in a kiln.
When buying wood the tree species could be a softwood or hardwood. Hardwood timbers are denser, and the logs produce a higher kW of energy than softwood, so will produce more heat and burn for longer.
Ashby only sell hardwood tree species as logs.
Kiln dried wood is dried slowly in an industrial kiln, this process removes excess moisture from logs and leaves a moisture content of 20% or below.
The short answer is yes, kiln dried wood burns hotter and more efficiently than other wood, due to the low level of moisture, so you need fewer logs to achieve the same output of heat. Kiln dried wood also offer a reduced risk of leaving residue tar inside your stove.
A seasoned log is timber that has been harvested, cut and air dried for 6 months to 2 years depending on species. Seasoning involves cutting wood into logs and then storing them in a dry, ventilated purposed built barn. Moisture content is then measured to know that the log is ready to burn.
A wet or fresh log only has about half the energy content of a dried or seasoned log, because energy is wasted dispersing water as it burns.
Fresh or wet wood is difficult to light and will burn very inefficiently. The high level of moisture in fresh wood creates smoke and more creosote when it burns which sticks to your chimney and this can cause long term issues with the flue.
Seasoned wood should be dry and have a low moisture content. Green or wet wood is freshly cut and will a moist appearance. Some woods carry more moisture when cut than others, Elm has the most at 60% moisture, 0ak has 50%, Beech has 45% and Ash has 35%.
Ash wood has a naturally low moisture content, making it the most efficient and therefore the most popular wood specifies. Kiln dried ash logs have a moisture content of around 15-20% and are easy to light, produce lots of heat, which lasts and produces a low level of smoke.
Ashby also supply kiln dried oak and beech solid wood. Beech has a smooth bark, making it easy to handle, this very dense wood has a bright yellow flame and lasts a long time. Solid oak is very dense and produces a great fire, sometimes it requires more air from the stove to maintain a good burn.
Solid wood species are better for firewood than softwood, this is because solid wood is denser, so you need less wood to produce the same level of heat.
Seasoned hardwood produces a high steady heat, and a great product for fireplace logs