Heating Resources
How to Get The Best From Your Woodfire
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.
Good Fuel Wood
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. Macrocarpa and gum are also excellent fuels although macrocarpa tends to spit 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 natural 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!
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 weight 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 harder wood.
Sourcing Fuel
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 have their crops pruned regularly, and often make the prunings and waste material available to the public. Farmers too, sometimes have felled trees 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. Remember though, burning of treated timber is an absolute No-No!
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 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"
Drying (or "seasoning") fuel
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 lighter the wood, the cleaner the burn, the less likely of creosote formation and less servicing is required for your appliance.
Seasoning Wood
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 of 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:
- Split larger logs, so that the largest surface area of the internal wood is exposed to the atmosphere.
- Stack the wood loosely, on bearers, with the ends facing a prevailing wind.
- Cover with a plastic sheet on a light frame to create a warmhouse effect, with the sides open to the prevailing breeze so it can flow freely through your stack
- Do not use it until it is fully seasoned
- Do not stack rotten wood - it has very little useful heat in it! If wood is put away wet it stays wet.
- Leave the bark on split wood - it helps to provide natural protection from rain.
- Make use of winter sunlight. Stack on the Northern face – sunny side of the house for best results.
Four ways to determine dry fuel:
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Knock two pieces of seemingly dry wood together. If it “rings” rather than “thuds” it is likely to be dry.
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Look for radial splits at the end of a piece of wood. These are a sure way to identify dry wood.
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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.”
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Place a piece of wood on your cheek – if it is cold – it still has a high moisture content.
About firewood
A piece of wood contains two totally different fuels which burn in quite different ways. The first parts to burn are the “volatiles”. These are the resins and creosotes etc. which are converted to flammable gases and smoke by the heat of the fire. Volatiles contain almost all of the pollution content of the wood.
The second part of the wood is the ember residue left after the volatiles have been burnt. This is charcoal, and it contains the major part of the heat content of the firewood. Charcoal burns easily and produces little if any pollution emissions.
If your heater is operating correctly most of the volatiles will burn properly, however if the fire and the ember bed is not hot enough they will not burn completely and exit the heater via the flue as unpleasant chimney smoke pollution. Take care to operate your fire so that it does not smoke and you will actually gain more heat from your firewood.
Creosote Formation and Flue Blockage
Creosote originates as condensed wood, resins and tar, often initially liquid, which dries to solid form and accumulates on the inside of the flue and at the base of the cowl. If a creosote build up has occurred in the flue, it should be removed to reduce the risk of a chimney fire.
Flue blockage from the formation of soot and creosote can be avoided:
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Light a fast hot fire to warm up your chimney so that any moisture in the smoke does not condense on the surface of the flue. Use plenty of small, dry kindling stacked to the level of the top of the firebricks, so that the fire warms the chimney as quickly as possible.
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Burn only dry wood, it will burn hot and fast without the problem of creosote build up.
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Keep your ash level under control. A nice bed of ash is good to insulate the coals, but too much will hinder the air flow for the firebox in your fire. Air flow is critical for providing oxygen for the burning process.
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Avoid burning wood with high resin content, such as Old Man Pine as Old Man pine wood is over 25 years old and has a higher Sap/gum content.
Operating Hints for Clean Burning and Best Efficiency
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As well as causing unhealthy air pollution, smoky fires waste money. A clean burning fire produces the most usable heat for the smallest cost. Smoke is simply unburnt fuel which is wasted.
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If you have an Inbuilt/Insert woodfire make sure the woodfire is insulated properly.
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For the Best Result – Keep your Woodfire Glass Clean as this gives more heat into the room. A dirty glass/film on the inside of the glass door will produce more wear and tear and retain heat inside the firebox.
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