Wood burners

Modern wood burners are highly energy efficient and produce limited air pollution. They use a form of renewable energy and so are essentially carbon neutral.

By comparison:

  • Open fires are often very inefficient - most of the heat is lost up the chimney. Open fires may warm the room they occupy a little bit, but create such a draft that they draw cold air into the rest of the house. Open fires also produce large amounts of air pollution
  • Older wood burners are less energy efficient and produce more air pollution.

Benefits of modern wood burners

  • It's one of the relatively cheap to run heating options, even if you have to purchase firewood. See indicative running costs for different home heating options in the Warm Healthy Home action sheet (PDF file).
  • If you have access to free firewood, your running costs will be close to zero.
  • Burning wood from sustainable forests is carbon neutral. While trees are growing, they capture carbon dioxide from the air. This carbon dioxide is released either when the wood is burnt, or when the tree dies and rots. While some emissions are produced in the transporting and processing of the wood, this is only a very small amount per unit of heat produced.
  • Wood is renewable and sustainable. New Zealand has extensive areas of forestry. Generation after generation of trees can be successfully harvested to produce firewood.
  • Wood burners will work during power cuts.
  • Some wood burners can be equipped with a wetback system to heat household hot water, check with your supplier about this option.

Checklist for choosing a wood burner

There are a number of things to consider when choosing a wood burner:

  • Insulate first. Make sure your ceiling and underfloor insulation is sorted first - your home will be easier and cheaper to heat properly.
  • Check with your local council and get a building consent. A building consent for the installation of a solid fuel burner will be required from the local city or district council. These authorities, including the regional council, may also have additional requirements for solid fuel burners, please check with them. Find their contact details on the Local council website directory.
  • Choose an authorised wood burner. Wood burners installed on properties less than 2 hectares in size must meet certain emissions and efficiency standards. Check out the Ministry for the Environment's list of authorised woodburners. Note that your local or regional council may have additional requirements, please check with them.
  • Work out what size you need. Most wood burners perform best near to their maximum output, so matching the size to the heating needs of the room is important. Modern wood burners usually meet the required emissions and efficiency standards by not being able to be damped down much. You need to take this into account if you are replacing an old wood burner. Use the free Consumer calculator to work out how much heat you need. EECA recommends seeking professional advice from your heating supplier.
  • Heating more than one room. Most wood burners generate much more heat than is needed for one room, but unless your house is very open-plan or has internal door openings which go right up to the ceiling the excess heat will not effectively travel into other rooms. Heat transfer kits, which are designed to extract warm air from one room and pump it into one or more other rooms, can assist with heat distribution. Heat transfer kits are available from DIY stores, but as there are a lot of factors that can affect how well they work, EECA suggests you contact a professional tradesperson.
  • Radiant or convective? Wood burners release their heat through a combination of heat radiation (heat objects) and convection (heats air). The amount of each varies from model to model.

    • Wood burners that are designed to primarily produce radiant heat will make the room they are in feel warmer than the air actually is. This makes them particularly suitable for large rooms with high ceilings and/or poor insulation and airtightness levels.
    • Wood burners that are designed to primarily produce convective heat will primarily heat the air around them which will then rise to the ceiling. This means you will get less heat in the bottom part of your room unless you use a ceiling fan to mix up the hotter higher and cooler lower layers of air. On the other hand convective heat will make it easier to move some of the warm air to other parts of your home.
  • Use a certified installer. Quality installation is fundamental to a wood burner's performance and safety. We recommend that installation be carried out by a certified Solid Fuel Appliance Installation Technician of the New Zealand Home Heating Association.

Use your wood burner wisely

  • Follow the manufacturer's operation and safety instructions.
  • Use safety guards to protect children. Woodburner surfaces can get very hot and can be a danger to small children.
  • Plan ahead and use well-seasoned, dry firewood. To burn efficiently it should be stored under cover in a well-ventilated and ideally windy and sunny place for at least a year to dry out before use.
  • Use the right wood at the right time. Lighter wood (often called 'softwood') wood like pine is good for making kindling and getting a fire started. Once you have a good bed of coals burning, denser wood (hardwood) will burn for longer and give more heat. Where possible, use wood from plantation forests (pine, gum, etc) rather than native types such as manuka.
  • Do not use chemically treated wood or salt impregnated wood such as driftwood. These can corrode your woodburner and flue and may also emit toxic gases when burnt and will leave toxic residues in the ash and flue.
  • Do not burn coal in a wood burner, unless the manufacturer specifically says you can do so. Otherwise you can damage your woodburner.
  • Regulate the heat output by adjusting the amount of fuel you load, not by dampening the air control.
  • Keep the air setting high enough for a clean burn. Too much or too little air cools the fire and smoke is produced. The cleanest burns will occur when large pieces of wood are placed on a good bed of glowing coals and the wood burner itself is at a high temperature.

What to do with your old open fire

If you have an open fire that you don't use, block up the chimney with some old newspapers to stop draughts. If you do block the chimney, try to make it hard, or impossible for someone to light a fire in the grate without realising the chimney has been blocked.

Maintain your wood burner

Whether you have got a modern or older wood burner, maintaining it regularly according to the manufacturer's instructions is important to maintain its safety, performance and longevity.Most wood burners and flue systems have parts that are designed to be replaced or cleaned periodically. It is also not uncommon to find wood burners that have been damaged from improper use or deferred maintenance such as from people burning coal in them.

Check with the manufacturer of your wood burner to see who they suggest for inspections and servicing. Otherwise contact the New Zealand Home Heating Association for advice.

More information

From the Resource Centre

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