Wood fuel in your home: 10 need-to-knows
Posted by Sandra Hayes on 29 November 2017 at 9:15 am
1. Fuel quality matters
To produce a clean, safe and efficient burn, quality of the wood is key. This is determined by size, moisture content, tree species and presence of any contaminants. Installing and maintaining a solid fuel appliance such as a wood stove is a big step so it only make sense to do it right. HETAS and Woodsure have produced a Quality Assured Fuel standard which includes a national database where you can search for registered suppliers in your area. The UK Pellet Council also operates a certification scheme for wood pellets known as ENplus, whereby quality is managed throughout the entire supply chain including production and storage of pellets.
2. Certain types of wood fuel are more suitable for use within the home
The four main fuels available to you are logs/firewood, briquettes, woodchips and pellets. Woodchips are not generally suitable in a domestic property because of the amount of space required for the equipment used for handling and storing them. Generally speaking, your heat demand would require a boiler with an installed capacity of at least 50kW before you would consider a woodchip boiler. If you have that, woodchips are a very cost-effective option.
A great place to start is the Forest Research’s introduction to types of wood fuel, which provides a practical overview of each fuel and whether it is appropriate based on your home’s size and heating requirements.
3. You can find sustainable and local sources of wood fuel online
There are a variety of online databases which you can use to find local and sustainable wood fuel suppliers.
The Carbon Trust hosts the National Biofuel Supply Database where you can filter suppliers by wood type and level of quality or accreditation. Alternatively, those needing logs for an open fire or wood-burning stove might try local tree surgeons as they often have surplus logs to sell as a side line.
For those considering biomass boilers, the Government’s Biomass Supplier List is a catalogue of wood fuel that has proven it meets the eligibility requirements for the domestic Renewable Heat Incentive.
4. If you’re looking to buy pellets, you will need to look at your existing heating bill
Obviously, a lot will depend on how energy-efficient the building is and how often the heating is on and the thermostat settings. Each tonne of wood pellets will produce approximately 4,800kWh of heat (assuming they're burned in a 100% efficient appliance). A small, energy-efficient home might only need 2 tonnes of pellets per year. – a larger, less efficient home might need something like three to four tonnes per annum. If you're thinking of switching to pellet heating, your existing heating bill will provide a useful guide to your consumption. Heating oil produces 10kWh of heat per litre (again assuming 100% appliance efficiency).
5. You can technically be self-sufficient in wood fuel
You would need to have sufficient land to produce 6 to 12 tonnes dry logs per annum. This could be done by planting a hectare of poplar which, after the third year, would produce approximately 10 tonnes of logs each year. However as this requires a large amount of space, for most a biomass boiler or wood stove will be used to supplement a wet (gas) central heating system.
6. The running cost of certain types of wood fuel is cheaper than electricity
It's always difficult to make comparisons between the cost of heating with different fuels, given that there are a number of different suppliers in the market, different electricity tariffs for day and night time and different costs according to the quantity of wood purchased and its delivery distance (particularly for solid fuels such as logs and coal).
In today's market, woodchip, wood pellets and logs are generally a cheaper way of heating than electricity, heating oil or LPG. In some instances, woodchips are also cheaper than natural gas. The price of biomass fuels like logs or pellets depends on your location, and changes over time depending on local demand and levels of production.
7. Biomass boilers burn most cleanly and efficiently when working at their maximum output
Sizing of heating systems should be done by a qualified heating engineer. It's dependent on many factors including levels of insulation and draught proofing of the building, the lowest outside temperature for your locality and patterns of use. However, the following 'rule of thumb' can be useful for making initial sizing estimates for central heating boilers:
Boiler size (in kW) = volume to be heated (in cubic metres) divided by 34 (for a reasonably well-insulated house).
Therefore, it's best not to over-specify but to choose a biomass boiler which is sized to meet your average heating requirements with additional heating sources to provide extra heat on the coldest days.
8. There are emissions produced from burning wood, but they can (and should) be minimised
The main emissions from burning clean, seasoned wood will consist largely of water vapour and carbon dioxide (plus nitrogen and oxygen from the combustion air). The emissions will also contain traces of carbon monoxide, particulates and volatile organic compounds, which can be exacerbated in the case of poorly-fitted stoves and wood burnt under the wrong conditions. These emissions are also produced when fossil fuels like gas and oil are burned to produce energy. However, this is not a reason to be complacent. Instead, it highlights the need to consider seriously the appliance that the wood is burned in and the quality of the wood fuel that is used. To ensure you stay safe when getting a wood-burning appliance installed, check out our database of trusted installers. After the work has been carried out, remember to test your carbon monoxide detector weekly too.
9. The level of emissions produced by your wood fuel system can affect your eligibility for the Renewable Heat Incentive
Biomass only boilers and biomass pellet stoves can only qualify for the domestic Renewable Heat Incentive if systems do not exceed the maximum permitted emissions limits of 30g per gigajoule (g/GJ) net thermal input of particulate matter (PM) and 150g/GJ for oxides of nitrogen (NOx). Systems installed between 15 July 2009 and the start of the scheme will not need to meet this requirement.
10. Wood can still be burnt in a smokeless zone, but only under certain conditions.
Wood can be burned in a smokeless zone if the appliance (stove or boiler) has an Exemption Certificate. Companies which manufacture log stoves with Exemption Certificates include Clearview, Vermont Castings, Dovre, Dunsley Yorkshire Stoves, Morso and Jotul.
There are also a number of pellet stoves and boilers that have Exemption Certificates. These include boilers and stoves manufactured by the likes of Binder, Extraflame, Fröling, Giles, Guntamatic, Hargassner, KWB and Solarfocus.
A full of list of appliances with Exemption Certificates can be found here.
Image credit: Richard Bates.
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