Sandra HayesIn the last few years, many of us have had a wood-burning stove installed in our homes to provide a living space that is both cosy and warm. As energy prices have soured many of us have also turned to a wood-burning stove as a cheaper alternative to turning on the central heating. A stove is a far more sustainable way of burning wood (a renewable fuel) than an open fire.
However, in recent years research into emissions from burning wood (and other solid fuels) has resulted in concerns about its impact on air quality. As a result of this, the government has introduced new regulations on the sale of stoves and solid fuel. This blog provides an overview of the emissions of greatest concern, what the regulations mean for existing stove owners, and whether it is worth considering a replacement.
Emissions
The emissions that are of most concern when wood is burned are particulates. Particulates are anything in the air that is not a gas and can therefore be formed of a very wide variety of chemical compounds. Particulate matter (PM) is present in the air in a range of sizes and is produced from a variety of sources including vehicles and agriculture.
The particulates that are of most concern due to their impact on human health are PM2.5. These tiny particles can get into the bloodstream, lungs, and other organs causing serious health problems.
This diagram has been copied from the government’s Clean Air Strategy of 2019. It shows the significant differences in emissions of PM2.5 between different types of appliances and fuels. Particularly notable are the difference in emissions between using a non-DEFRA exempt and a non-DEFRA exempt stove. Only a DEFRA-exempt stove can be used in a smokeless zone due to their lower emissions.
Further information on the impacts on health from wood-burning stoves can be found in this article from Which?
If you would like to listen to one homeowner’s experience of emissions from PM2.5’s from his new wood burner this YouTube clip is well worth a listen. Particularly interesting are the measurements of PM2.5 he got when the stove was new.
Fuel
The type of fuel you burn in a stove has a significant impact on emissions. Burning wet wood produces far more emissions (and less heat) than burning dry (seasoned) wood. Wet wood is also much more likely to produce deposits of tar in the chimney, which increases the risk of a chimney fire. Wood that has been treated in any way should never be put onto a wood-burning stove due to the chemicals that are released when it is burned.
Since 1st May 2021, the sale of wet wood in quantities of less than 2m3. has been banned in England. In addition, wood sold in quantities of 2m3 or less must now be certified as Ready to Burn. Wood that has been certified as Ready to Burn must have a moisture content of 20% or less. Suppliers and useful information on the storage of wood and measuring moisture content can be found on the Ready to Burn website.
Sales of more than 2m3 of unseasoned wood are legal, but advice must be given on how to season the wood. If you buy your wood in this way or collect your own, a moisture meter is cheap and well worth the investment to ensure that you only burn dry wood.
Stoves
As well as regulations on the sale of wood the government also brought in regulations on the efficiency and permissible level of emissions from the use of a new stove. These Ecodesign Regulations came into force on 1st January 2022 but only apply to the sale of new stoves.
In addition to DEFRA Exempt and Ecodesign stoves, there are voluntary certification schemes in the UK for stoves such as clearSkies and the Heatus Cleaner Choice Approval Scheme. The clearSkies scheme has four levels, two to five. All clearSkies stoves are Ecodesign complaint, but only levels three and above also meet the requirements of DEFRA exempt. ClearSkies say that stoves certified by them produce up to 90% lower emissions than an open fire and up to 80% lower than the average 10-year-old stove.
If you are wondering whether you should be replacing your wood-burning stove with something that burns more efficiently with fewer emissions, we suggest that you take the following steps:
Check whether your stove is on the list of DEFRA Exempt stoves or even better, on the clearSkies list (the PM limit for Ecodesign stoves is 55% percent lower than the limit for DEFRA exempt stoves).Obtain an air quality monitoring tool to establish the levels of gases and PMs present in the room when the stove is on. It is worth noting that prolonged exposure to PM levels above 50 can lead to serious health issues and premature mortality.Assess the overall condition of the stove – does the door close properly, are there any cracks in the glass, are there any holes in the bodywork or anywhere else that emissions can escape from the stove into the room?Ask yourself if you are comfortable in the room when the fire is on or does the room get too hot and stuffy? Do you find yourself constantly reducing the flow of air to the fire to bring the temperature down? If you cannot comfortably use your stove at maximum output this will result in more emissions and soot deposits. It is also a sign that your stove is too big for your room.
If your stove is not on one of these lists, or air quality monitoring reveals PM (or other emissions) at a level of concern or your stove is in poor condition or it is too big for your room, we would advise that you seriously consider getting a replacement for your stove or stop using it. A HETAS registered installer will be able to give you further advice on this.
Summary
In short, you can continue to use your existing wood-burning stove, provided you burn only clean dry wood on it. You do not have to replace your existing stove because of the Ecodesign regulations, but you may wish to consider it for the reasons set out above.
Given higher levels of emissions from burning wood compared to oil or gas, it does make sense to limit the use of your wood-burning stove to occasional top-up heating unless you have one of the best-performing stoves on the market. This is particularly pertinent if you live in a smokeless zone or anywhere else where outdoor air quality is of concern.
