Wood Burning Properties

Wood Burning Properties

There are a many types of wood to choose from, all of which have their own burning qualities and properties. Although there are references to burning green wood here; to get the most efficient and effective ‘burn’ in your wood burning stove, only very dry (at least <20% moisture) wood should be used. Wood always burns best on a bed of its own ashes, the following is a small guide only and by no means comprehensive.

In addition there are also the compressed reclaimed ‘eco’ type of logs and briquettes which do tend to burn well and for a decent length of time because they are dense and very dry. However, you should try to choose a product that does not break apart too easily.

The table below shows the types of woods and their properties.

Alder Produces poor heat output and it does not last well. Poor
Apple A very good wood that bums slow and steady when dry, it has small flame size, and does not produce sparking or spitting. Good
Ash* Reckoned by many to be one of best woods for burning, it produces a steady flame and good heat output. It can be burnt when green but like all woods, it burns best when dry. Very good*
Beech* Burns very much like ash, but does not burn well when green. Very good*
Birch Produces good heat output but it does burn quickly. It can be burnt unseasoned, however the sap can cause deposits to form in the flue with prolonged use. Good
Cedar Is a good burning wood that produces a consistent and long heat output. It burns with a small flame, but does tend to crackle and spit and the sap can cause deposits to form in the flue with prolonged use. Good
Cherry Is a slow to burn wood that produces a good heat output. Cherry needs to be seasoned well. Good
Chestnut A poor burning wood that produces a small flame and poor heat output. Poor
Firs (Douglas etc) A poor burning wood that produces a small flame and poor heat output and the sap can cause deposits to form in the flue with prolonged use. Poor
Elm Is a wood that can follow several burn patterns because of high moisture content, it needs to be dried for two years for best results. Elm is slow to get going and it may be necessary to use a better burning wood to start it off. Splitting of logs should be done early. Medium
Eucalyptus Is a fast burning wood. The sap can cause deposits to form in the flue and can increase the risk of a chimney fire if burned unseasoned. Poor
Hawthorn* Is a good traditional firewood that has a slow burn with good heat output. Very good*
Hazel Is a good but fast burning wood and produces best results when allowed to season. Good
Holly Is a fast burning wood that produces good flame but poor heat output. Holly will burn green, but best dried for a minimum of a year. Poor
Hornbeam A good burning wood that burns similar to beech, slow burn with a good heat output. Good
Horse Chestnut A good wood for burning in wood stoves but not for open fires as it does tend to spit a lot.  It does however produce a good flame and heat output. Good (For stoves only)
Laburnum A very smokey wood with a poor burn. Poor do NOT use
Larch Produces a reasonable heat output, but it needs to be well seasoned. The sap can cause deposits to form in the flue with prolonged use. Medium
Laurel Burns with a good flame but only reasonable heat output. It needs to be well seasoned. Medium
Lilac Its smaller branches are good to use as kindling, the wood itself burns well with a good flame. Good
Maple Is a good burning wood that produces good flame and heat output. Good
Oak Because of its density, oak produces a small flame and very slow burn, it is best when seasoned for a minimum of two years as it is a wood that requires time to season well. Good
Pear Burns well with good heat output, however it does need to be well seasoned. Good
Pine (Including Leylandii) Burns with a good flame but the resin sap can cause deposits to form in the flue and can increase the risk of a chimney fire.MUST be well seasoned. Good (with caution)
Plum A good burning wood that produces good heat output. Good
Poplar A very smokey wood with a poor burn. Very poor
Rowan* Is a good burning wood that has a slow burn with good heat output. Very good*
Robinia (Acacia) Is a good burning wood that has a slow burn with good heat output. It does produce an acrid and dense smoke but this is of course not a problem in a stove. Good  (For Stoves only)
Spruce Produces a poor heat output and it does not last well. Poor
Sycamore Produces a good flame, but with only moderate heat output. Should only be used well-seasoned. Medium
Sweet Chestnut The wood burns ok when well-seasoned but it does tend to spit a lot. This is of course not a problem in a stove. Medium (For Stoves only)
Thorn* Is one of the best woods for burning. It produces a steady flame and very good heat output and produces very little smoke. Very good*
Willow A poor fire wood that does not burn well even when seasoned. Poor
Yew* A good burning wood as it has a slow burn and produces a very good heat output. Very good*

Moisture Meters

The single worst predisposing cause of chimney fires today is wet wood. The recommended level of moisture is less than 20% to avoid chimney fires. You can read more about moisture meters here >(Moisture Meters)

This guide was originally taken and adapted from http://www.flamingfires.co.uk/which-wood-burns-best.htm

Using stove thermometers to ensure optimum efficiency

Using stove thermometers to ensure optimum efficiency

Using your newly acquired wood/multifuel stove , will give months of long , easy  & warm cosy days , where you can lounge around just enjoying yourself. However, as with all things that are subject to temperature variations, maintenance checks are essential giving you peace of mind and satisfaction everything is running to optimum conditions.

Often times these, “checks” may seem as if they might drag you out of your comfort zone but the good news is, in using a stove thermometer, it’s as simple as making regular readings once you’ve attached it to the stove top or flue pipe arising from the stove. They come in a few varieties and can be wire , hose clipped or magnetically attached.

ChimGard Stove Pipe ThermometerFigure:1 Typical stove thermometer (with orange goldielocks zone)

They are used primarily to avoid over firing, the resulting extreme temperatures created and bad fuel efficiency. Operated by having a eye gauge in both °Celsius and Fahrenheit. Keeping your stove burning in the Correct range of 115°C – 245°C or  (240°F – 475°F) will ensure the safest operation , whilst simultaneously giving maximum fuel economy.

Running Too Cool

Allowing your stove to reach burning temperatures below 115°C or (240°F) will lead to incomplete combustion creating carbon monoxide, tar, soot and creosote.

Creosote , itself is a condensation residue of coal and/or wood particles, hydrocarbons, gases and other airborne debris. It is formed as gases cool , for example when air in a chimney is not hot enough to push the particles out. Its appearance is of a thick hard black shiny goo which reduces the bore of the flue by sticking to the inner bore.

Running Too Hot

When you allow your stove apparatus to run above burning temperatures of 245°C or (475°F) you risk damage; warping your grate and also to your flue/liner/cowl too.  A significant increase of the risk of chimney fires is created, especially if there has been creosote build up.

Read our other articles under ‘stoves’ or burning ‘wood’ to get all the knowledge you need to use your appliances to maximum efficiency and safety. Also Please remember to get your solid fuel heating appliances swept at least once a year by your chimney sweep.

You can buy thermometers and wood moisture meters here Here

Whats the difference a multi fuel or just wood burning stove?

Whats the difference a multi fuel or just wood burning stove?

Traditionally, wood-burning stoves were intended to burn wood and only wood.However, multi-fuel stoves were created to give you the option of heating your home with either coal or wood.
Now first off, it is really NOT advisable to burn both coal and wood in your stove at the same time as this can and will damage your flue lining. The high amount of sulphuric acid found in coal and the moisture levels in wood will combine to create a nasty, acidic solution that sticks to and erodes your stove system. So multi-fuel stoves bring with them the versatility of being able to choose which fuel you’d rather use at a particular time but only one or the other.

Using just coal?

Firstly, you should always check your owner’s manual for the final word from the manufacturer on what fuels are recommended for use in your stove.
While most multi-fuel stoves are equipped to burn normal house coal, often stove manufacturers will advise against this because of the high amount of soot found in house coal. This high soot content results in your stove system becoming
rapidly clogged up.To avoid this, you can use smokeless coal to reduce the amount of smoke and soot going up your flue, this is also better for the environment and suitable for use in smoke control areas.

How to know which stove is which just by looking at it, physical differences you can see by eye.

The most obvious example is the grate in the multi fuel burner. Coal burns best on a raised grate since it needs an air supply from below to burn effectively. Wood doesn’t need this additional air supply, therefore, wood burners come with a flat grate limiting the air supply to the fuel, resulting in a slower burn.
Using wood on a multi-fuel stove you will find that it burns faster than on a normal wood-burning stove because of this extra air/oxygen around it.If multi-fuel stoves were the most effective method of burning wood, then modern wood- burning stove designs would have become redundant years ago.Multi-fuel stoves exist because they have been designed for the purposes of burning coal.

So what do i want to buy then?

In short what to buy depends on what you are going to burn? If you’re thinking of using wood as your main fuel then it’s best to buy a wood-burning stove.
By buying a multi-fuel stove, you’ve already committed to coal being your main fuel (but keeping the option open to burn wood if need be, albeit at a lower efficiency).
Therefore for the reasons already mentioned above, smokeless coal is your prime candidate fuel for a multi fuel stove.
So you will be considering anthracite, as well as a host of brand name alternatives such as Taybrite and Phurnacite.

The Cost of Wood as a fuel

The Cost of Wood as a fuel

For the best results, wood should be left on a dry surface protected from rain but with the sides exposed to air and wind. It should be stacked not piled which will speed up the drying process. Chopping the wood down to size before storing it will also help it to dry quicker. Alternatively, you can buy ready-seasoned wood at a little extra cost. Remember , burning wet wood is the quickest way to a chimney going on fire!! so its wise to use a firewood moisture meter to ensure it is below 20%.

  • Freshly cut logs are cheap to buy at around £80 per cubic meter but have a moisture content between 60% and 90%. The heat output from freshly cut logs will be around 1 kWh per kg.
  • Ready-seasoned wood has around 40% moisture content and can usually be purchased for around £95 – £123 per cubic meter. Burning wood that has been seasoned will give you a heat output of about 3 kWh per kg.
  • Alternatively kiln-dried wood is more expensive, about £115-£145 per cubic meter but is highly efficient and can be used immediately. On average, it contains less than 20% moisture and burning it produces a heat output of around 4.5 kWh per kg.
  • If you have a specialised wood-pellet stove, you can usually buy wood pellets online or from a local supplier. Wood pellets are sold by the tonne and cost around £140-£190 per cubic tonne. The Stove Industry Alliance (SIA) recommends that you buy ENplus standard pellets, which have roughly 10% moisture content and will give you a heat output of around 5 kWh per kg.

Kindling can be sourced from pallets used for building suppliers and found in skips (just check with the owners first).It’s also worth considering if whether the wood has been treated with chemicals because it could be unsafe to burn.Also please remember to remove all nails.

Note: 500kg is around one cubic meter, so working out how much wood will cost for the amount you’ll use can be a little tricky. However, as a rough guide an average-sized house which uses a stove in the evenings and at weekends, will need about three to four cubic meters a year.

Although wood itself is considered a carbon-neutral fuel, transporting it uses CO2, so it’s best to try and find a supplier close to home.

Things the customer should consider burning wood when it comes to sweeping

  1. You should only burn seasoned HARD woods, the moisture content (easily checked with a cheap and commonly available moisture meter) should be less than 20%, ideally 15%.

  2. The soot particles from burning wood are very often extremely reduced in size and akin to plant pollen. This means it can be very difficult to control the extraction of the residue because they form a floating cloud.
    Any change in air flow (e.g. opening of room doors or windows) during the extraction process can result in the escape of particles from the fireplace.
    Hence it is suggested that all immediate items around the fire are removed and suitable covers for furniture e.t.c. are put in place (using common sense) by the customer prior to the sweeping appointment.