The key to a good fire – which means good efficient burning and heat transfer is to make sure that your fuel is as dry (or “seasoned”) as possible.
It doesn’t really matter too much what SORT of fuel you use on your fire, but we recommend in the interest of the environment, that you avoid the use of native timbers for fuel – particularly as New Zealand has an abundant supply of exotic trees which make admirable fuel. So too, does demolition material..
But you must avoid:-
- The use of salt borne drift wood. The salt absorbed into the wood reacts with the flame and other by-products to cause damage to the heater system and its componentry. For the same reason, chemical chimney cleaners should be avoided, as many of these comprise a high level of salt in their make-up.
- Chemically treated timbers should also be avoided. At best they generally don’t burn as well as untreated fuel. At worst, some of the chemicals may be noxious and pose a health risk! Don’t take the chance!
- Weight for weigh all timber has about the same heat capacity, so it doesn’t matter if you burn hard or soft wood – all it means is that if you use softwood, you’ll use more volume of fuel for the same amount of heat you will get from more solid fuels.
The good thing about a wood heater is that you can often gather enough timber to see you through the coldest winter for nothing or at least a minimal cost. Commercial forests prune their crops regularly, and often make the prunings, and waste material available to the public. Farmers too, sometimes have felled tres that they are keen to get rid of. And if you live in the city, look round for house renovations – there are many places where people are only too willing to have unwanted timber removed free.
But some people will find it more convenient and economic, to purchase their supplies from a timber merchant. If this applies to you, purchase your fuel as far out from the coming winter as you can – that way it has time to dry more thoroughly.
Don’t expect the wood you may obtain in the middle of winter to be dry and burn well! And from a purely economic point of view, try to avoid buying small quantities of bagged fuel. This is an expensive way to buy, and more often than not, it will still be “green”.
Simply because the outside of a piece of wood is dry on the outside, it doesn’t mean that it is dry enough to burn. Converesly, even if the outside is wet, if it is seasoned properly, it will often burn beautifully!
And the drier the wood, the cleaner the burn, the less likely is creosote formation, and less servicing is required.
If you are starting with “green” wood, there are a few steps to take to ensure that it will be just right when you come to burn it!
Remember that green wood can hold its own weight in water, and it takes time to get rid of this. Hardwoods take about twice the length of time to dry than softwoods. Count on about 6-12 months for woods such as pine, and 12 months to two years for hard woods .
A few tips:
1. Split larger logs, so that the largest surface area of the internal wood is exposed tot he atmosphere.
2. Stack the wood loosely, on bearers, with the ends facing a prevailing draft.
3. Cover with a plastic sheet on a light frame to create a warm house effect, with the sides open to the prevailing breeze so it can flow freely through your stack.
4. Do not use it until it is fully seasoned.
5. Don’t stack rotten wood – it has very little useful heat in it!
6. Leave the bark on split wood – it helps to provide natural protection from rain.
Three ways to determine dry fuel:
- Knock two pieces of seemingly dry wood together. If it “rings” rather than “thuds” it is likely to be dry.
- Look for radial splits at the end of a piece of wood. These are a sure way to identify dry wood.
- 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”.
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 splutter and spark more than a lot of other fuels and in appliances with fixed secondary burn chambers this may cause servicing problems because of fly ash.
We suggest avoiding native timber for fuel, unless it becomes available through demolition or natrural attrition. Manuka though, is considered a nuisance timber in some areas, and could be used for fuel. It is indeed good fuel – provided it is dry – but remember, drying manuka will take a long time. Look for the radial cracks at the end of the logs!