A wood stove run properly is efficient, clean and pleasant. Run in the way most people run one, it wastes a large share of the fuel, coats the flue in tar and produces a great deal more smoke than it needs to.
The difference is almost entirely two habits: burning dry wood, and burning it hot with enough air rather than shutting it down to smoulder.
Before you light anything
Also before the first fire of the season:
- Have the flue swept. At least once a year, more if you burn a lot or burn softwood. See sweep and inspect a flue.
- Check the door rope seal. Close the door on a sheet of paper; if it pulls out easily, the seal has gone and the stove is drawing air it cannot control.
- Check the baffle and the firebricks are present and intact.
- Look up the flue for nests, and check the cowl.
- Clear the hearth. Nothing combustible within the required distance, and a spark guard if there are children or animals.
Dry wood is the whole thing
Wood above about 20% moisture content is not fuel, it is a problem.
Water in the wood absorbs heat to evaporate, so the fire burns cooler, less of the energy reaches the room, and the volatiles that should burn go up a cold flue and condense as tar.
Season it properly: split, stacked off the ground, covered on top but open at the sides, in a windy sunny place, for one to two years depending on species. See split, stack and season firewood.
Buy dry, or buy two years ahead. Wood sold as seasoned frequently is not, and a moisture meter pays for itself on the first delivery.
Bring tomorrow's wood indoors today, so it is at room temperature and surface dry when it goes on.
Lighting it
Top-down. Larger pieces at the bottom, smaller above, kindling above that, firelighter or tinder on top.
It is counter-intuitive and it is better: the fire burns downwards, the flue warms quickly, the smoke from the wood below passes up through the flames above and is burnt, and there is far less smoke and far less tar. See light a fire top-down.
- All the air controls fully open.
- Door slightly ajar for the first few minutes if the manufacturer permits it, to get a strong draught going. Never leave it unattended like that.
- Warm the flue first if it is cold and the stove is reluctant: hold a lit taper or a twist of burning paper up inside the throat for a minute to establish the draught and stop smoke rolling into the room.
- Get it properly hot before you touch the controls. A quick hot start produces a fraction of the tar of a slow smoky one.
The air controls
Most stoves have two or three, and knowing which does what changes how the stove behaves.
- Primary air, usually under the grate, feeds the fuel bed. Needed for lighting and largely closed once established for wood, which burns best on a bed of ash with air from above.
- Secondary air, usually across the glass, burns the volatile gases coming off the wood and keeps the glass clear. This is the one that stays open for wood.
- Tertiary air, where fitted, feeds the top of the firebox for a final clean burn.
The reading you want is the flame. Bright, lively and reaching upwards, with clear glass. If the flames go lazy, dark yellow and rolling, or the glass blackens, it is starved of air. Open it up.
Do not run it on primary air alone with the secondary shut. That is smouldering, and it is the tar-producing state.
A stove thermometer on the flue pipe is genuinely useful and inexpensive: it shows the band where the stove burns cleanly, below which you are tarring the flue and above which you are overfiring it.
Refuelling
- Little and often. Two or three smaller logs on a hot bed beats one large log with the air shut down.
- Refuel on embers, not on ash. Rake the embers forward, put the wood on, open the air until it catches properly, then set it back.
- Open the air before you open the door, and open the door slowly, to avoid a puff of smoke into the room.
- Do not fill the firebox. Leave room for air and flame above the wood.
- Let it burn bright after each refuel rather than damping it immediately.
Overnight
A wood stove is not designed to run unattended overnight, and trying to make it do so is the source of most of the problems on this page.
- Damping right down does not store the heat, it wastes it. The volatiles go up the flue unburnt.
- It coats the flue in tar, which is the fuel for a chimney fire.
- It produces a great deal of smoke, which is a genuine nuisance and an air quality problem for the whole street.
- And it means a fire burning while everybody sleeps, which is the carbon monoxide case above.
Better: burn it hot in the evening, let it go out, and rely on the heat stored in the room and the fabric. Layers, hot water bottles and shared bedding do the rest. See make one warm room.
If you genuinely need overnight heat, that is what a stove with a large thermal mass is for, or a rocket mass heater, which stores the heat in masonry rather than trying to slow the fire.
Ash and maintenance
- Leave a bed of ash a couple of centimetres deep. Wood burns better on ash, and it protects the base.
- Empty before it reaches the air inlets.
- Ash goes in a metal bin with a lid, outside, on a non-combustible surface. Embers stay live for days, and ash in a plastic bin or a cardboard box is a recognised cause of house fires.
- Wood ash is useful: for the compost heap in small quantities, and for lye. Coal ash is not.
- Clean the glass with damp newspaper dipped in cold ash, which is free and works better than most products.
- Replace the door rope when it flattens, annually if the stove is used hard.
- Check the firebricks and the baffle each season.
- Sweep the flue at least once a year, and twice if you burn heavily.
Chimney fire
Getting more heat out of it
- Dry wood. Everything else is second to this.
- A stove fan on top moves the heat off the stove and into the room, and needs no power.
- Do not put the sofa against the stove. Let the air circulate.
- Reflect heat forward with a plate behind the stove where the installation allows.
- Keep the door shut. An open door loses most of the heat up the flue and is the least efficient way to run a stove by a wide margin.
- Close the room off and heat one room properly rather than the hallway.
- Insulate and draughtproof, which is worth more than any amount of extra fuel. See draughtproofing, and mind its warning about vents.