Woodburner pros and cons

Is a woodburner right for you? Here's what to consider.

Stack of firewood

The large amount of radiant heat produced by a wood-burning fire suits many of our houses – especially older, poorly insulated and draughty homes with high ceilings. A properly sized and installed woodburner can heat the whole home.

Many people also like the toasty radiant heat a woodburner produces. Some models can heat hot water and all of them can be used during a power cut. Many have a flat top surface for heating a kettle – or even for emergency cooking.

Burning wood is carbon-neutral because it's a renewable resource, but burning it cleanly is the key to making it enviro-friendly.

By burning dry wood in a clean-burning woodburner you win 3 times over:

  • Wood is a sustainable heating fuel.
  • You get more heat from a clean-burning (non-smoky) fire.
  • Cleaner burning means fewer smoke particles lodging in all our lungs.

That’s the positive stuff. The flip side of woodburners is their contribution to air pollution and their relative lack of convenience.

If you burn wood carelessly or burn wet wood you can create a health hazard through ultra-fine pollution lodging in people's lungs. Modern woodburners can burn much more cleanly than older models. But our tests have shown that clean burning only occurs if the fire is carefully tended – and with the right-sized dry wood.

Air pollution is not inconsequential. The ultra-fine soot particles in wood smoke are a health hazard. They can lodge deep in the lungs causing premature death, hospitalisation and respiratory illness. It’s not just the people of Christchurch and Nelson who are at risk: there are many monitored areas (“airsheds”) where there are health risks from wood-fire pollution.

Woodburners aren’t as convenient as heat pumps or central heating systems. You “regulate” the room temperature through the amount of wood you burn and there’s no timer-controlled automatic starting system. You also have to buy firewood in advance and store it.

If you're about to buy a woodburner, here's what to consider:

Type

Freestanding models are generally the most efficient (for a given firewood load, they return the most heat to a room). They're also the cheapest to install. But if you have an existing open fireplace, an insert model is most often the way to go. Although insert models are not as efficient as freestanders, they're way better than an open fire.

Heat output

If you have a non-draughty well-insulated home in the north of the North Island then 10kW should be plenty. A larger house – or the same-sized but less-well-insulated and draughty house – further south will require 12-14kW.

In non-open-plan houses there's no point in overheating the lounge while the rest of the house stays cold. Install a heat-distribution system to help spread the heat throughout the house.

Be careful about manufacturers' heat-output claims – some grossly exaggerate what you'll get. Always check the compliance plate. This has to be on every woodburner that's sold – and it states the tested heat output, along with the efficiency and emissions rate.

Convector vs radiant

All woodburners both heat the air and radiate heat on to objects that are within a few metres of them. But some woodburners are marketed as predominantly one type or the other. It depends on the external design of the firebox. Convectors are best for well-insulated non-draughty houses with low ceilings. Radiant-type models suit older and less-well insulated (or draughty) houses with higher ceilings.

A convector heater heats the air immediately around it. Hot air is lighter (less dense) – so it rises away from the heater and gets replaced with cooler air which is in turn heated. This convection air-current means that the warmest air in the room ends up near the ceiling with the coolest air near the floor. Convector heaters are air warmers.

A radiant heater “shines” heat on to anything in its path. That could be you if you’re near the fire, or furniture within a few metres of the fire.

Controls/cleaning

The controls should operate smoothly, and it should be relatively easy to clean the outer surfaces and empty the firebox.

Flue system

The flue must have a larger diameter outer shield around it where it passes through the ceiling and attic space. Some of the newer designs have this air-gap vented outside rather than into the room (outside venting stops hot air escaping from the room). Some other woodburners get the air needed to burn the wood from outside the house rather than from within the room: this improves efficiency and reduces drafts.

Emissions

The lower the particulate emissions from your fire, the less of a health hazard you'll be causing. You can find this out from the woodburner's compliance plate.

Wetbacks

A wetback uses copper pipes to circulate water from the woodburner to the hot-water cylinder and back. They're expensive to install and the hot water cylinder needs to be placed reasonably close to the burner. The payback period for a wetback depends on how you use your woodburner: if the woodburner's not used every day, a wetback is unlikely to be cost effective. See our section on wetbacks for more information about this type of woodburner.

Safety guards

Woodburner surfaces can get very hot and can be a danger to small children. Protective guards are available, and highly recommended.

Building consent

Before you buy a woodburner, make sure your local authority will allow you to install the model you want: some councils will only allow installation of models from their recommended list. You will also need to get a building consent before you install your woodburner (you're unlikely to get one retrospectively). If an illegally installed wood-burner causes a fire, it may invalidate your insurance cover.

Installation

A poor woodburner installation job can ruin the heating and emissions performance of the best models. Check that your woodburner installer has New Zealand Home Heating Association certification or is otherwise suitably experienced.

Heat transfer

A heat-transfer kit usually removes warm air from the lounge and ducts it to a colder part of the house. Alternatively it can be set up to duct cold air from elsewhere in the house and deliver it to the lounge for heating. Either way the doors must be left open or ajar so that the air can circulate and even out the temperatures.

More on woodburners

More on woodburners

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More on woodburners

Find the best woodburner for your needs, learn how we test them and calculate the right size for your home.

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John M.
12 Jul 2020
Are the new burners all that much better?

Encouraged or should I say forced to change our woodburner, we chose the woodsman tarras MK111. Sorry I think it is a crock compared to the old Kent burner. my neighbour changed his at the same time with identical burners, except that mine has a wetback and his doesn't . We agree on all points. The woodsman is capable of giving out good heat, but it is uncontrollable. If you fill the firebox up, after all the wood has caught, close the damper; It still roars away, putting out the heat but chewing through the wood like crazy. Put only 2 or 3 slabs of wood in, gives a little less heat and burns less wood in the evening, but you have to get up every 15 minutes to feed it. (keep warm by jumping up to feed it!) The Kent was not effected by the quantity of wood you put in, you could control the rate of burning and heat output with the two dampers (only one on the woodsman.) That's no 1 problem. No 2. The woodsman is a filthy fire to operate. No matter how you load the firebox, every time you open the door, ash falls out! The Kent would actually suck the ashes inwards when you open the door. The woodsman would often emit a puff of smoke into the room or ash flakes into the air when the door is opened. The manufacturers suggested the flue joints were not sealed. The installer assured us the joins were sealed. We find we are sweeping the flue more frequently. And both the neighbour and I will swear the smoke emissions are no different between the old fires and the new. We would both have our Kents back in a flash!

Bevan M.
02 Aug 2020
Thanks for comparison

My wife is making noises about upgrading our kent fire with a modern one... I am not rushing out to buy anything just yet until I have seen a few fires working and make my comparison from that and yes it pays to talk to different people about their experiences.

Steve B.
30 May 2020
No Brainer

If there's free firewood about a woodburner is a no brainer.

We installed a Kent Kea Rad 11 with the help of a builder friend. The woodburner is not big and was bought only because it was on special, even that can push out far more heat than is needed.

We forwent the kent flue and bought a "quiet one" that doesn't roar in a high wind - this has turned out to be an excellent choice. Kent "at the time" in its wisdom threaten buyers of these flues by cancelling the warranty.

Kent were also confusing as they stated that a 50mm hearth was required when only an ash floor protector was needed.

We made up our ash protector using some 6mm cement board with tiles of our choice glued and grouted on top.

We made a slight blue on the positioning of the woodburner by putting it in the centre of a wall rather than a corner. Corner is better.

Sods law also said that where we wanted it meant we had to shuffle it a bit due to ceiling rafters, electric cables, roof rafters and the lie of concrete tiles. There is just no way anyone will miss all of these hazards which need to be worked around.

If buying lead sheeting for the roof, buy a bigger bit, even so a big chunk is wasted after cutting out the chimney from the middle of the sheet.

Doing it all again would also put in some sort of a heat transfer system to warm up the other end of the house.

We bought the woodburner first and only later a heat pump.

Yes and the council permit is a must to keep the house insurance valid.