The most important factor is the moisture content of the wood. A moisture content of 20% has been adopted as the industry standard and this is what stove efficiency figures are based on. Variations in moisture content will have a great effect on the way the stove burns so the drier the wood the better.
Hardwood grows slowly and is therefore a more dense fuel, burning for longer.
Softwood is faster growing and is therefore a less dense material so it will ignite and burn quicker.
To get improved efficiency kiln dried wood can have as low a moisture content as 10% and subsequently burns very well which you will pay a premium for. Ideally it will be stored indoors – as it has been dried artificially if it is left in a damp environment nature will take its course and moisture will be drawn back in like a sponge.
Heat logs can also be used – these are reconstituted wood made out of the sawdust from wood manufacturing and forestry. As these are artificially made they have a similar moisture content to kiln dried wood, around 10%.
