What is the best type of wood to use?
A number of things should be considered when using wood for heating. An understanding of the various types of wood fuel that is available including its advantages and limitations, and it is essential to know how to light and maintain a good fire.
Wood fuel ranges from soft woods like pine, to hardwoods like manuka. But whatever wood is chosen, the key to a successful fire is to ensure the fuel is as 'Dry', or as 'Seasoned', as possible.
Green wood can hold up to its own weight in moisture and sap and it takes time to get rid of this.
While surface water does not really matter because that will evaporate quickly, it is important to reduce the sap levels within the cell structure of the wood itself. Softwoods will season quite quickly, in about 6 to 12 months, but it can take for 18 months to 2 years for hardwoods such as Manuka to dry to an acceptable level.
Most woods make suitable fuel, pine is common and good its high resin content and loose cellular structure means it burns faster than some others, so be prepared to make more trips to the wood shed. Macarocarpa and gum are also excellent fuels although marcarocarpa tends to spit and spark more than a lot of other fuels and in some appliances this may cause servicing problems because of fly ash.
It is suggested avoiding native timber for fuel, unless it becomes available through demolition or natural attrition. Manuka though, is considered a nuisance timber in some areas of New Zealand, and could be used for fuel. It is indeed good fuel - provided it is dry - but remember, drying Manuka will take a long time.
If you knock two pieces of seemingly dry wood together if it "rings" rather than "thuds" it is likely to be dry, regular use of a moisture meter will ensure you know just how dry your wood fuel is. However simply because a piece of wood is dry on the outside, it doesn't mean that it is dry enough to burn. Conversely, even if the outside is wet, if it is seasoned properly, it will often burn beautifully. The drier the wood, the cleaner the burn, the less likely is creosote formation and unburnt smoke being exhausted from the flue.
Place a piece of timber on a good fire base if three sides are burning within 15 minutes, the fuel can be considered to be "dry."