6 things to consider before buying a wood burning stove
Posted by Laurence Jones on 17 March 2011 at 9:06 am
More and more people are turning to stoves to heat their homes. Biomass fuels such as firewood have been growing in popularity as a carbon-lean heating solutions as consumers aim for a more ecocentric outlook for their homes.
However, the importance of buying a suitable appliance for the job, is something we often don’t give our full consideration.Looking past the aesthetics of a modern appliance, these are the criteria you should have in mind when shopping for your next stove.
1. Heat output: is the stove the correct size for the room it is heating?
Different output stoves are designed to heat different sized spaces. A typical kW rating for a stove that heats an average room is around 4-5kW, where as a stove with an 8kW rating is designed for a much larger space. You should also consider the age of the house and any efficiency-saving measures that are in place. A newly built house may only require a fraction of the output from a stove that an older building will.
2. How efficient is the stove?
Building regulations in the UK set minimum efficiency levels for all new heating appliances. The efficiency of a stove is measured by how well an appliance can extract the available heat in the fuel and deliver it to the living space as useful heat. Efficiency can be quoted either on a net or gross basis. The difference between these two values depends upon how the initial heat content of the fuel is calculated.
The minimum gross efficiency required for a dry stove (see below for more details) is 65% and for a stove incorporating a heating boiler it is 67%. Many stoves are able to achieve higher efficiencies than this and values in the 80s are now commonplace.
3. Frequency of refuelling - intermitent or continuous stove?
‘Continuous operation’ stoves must be able to demonstrate a minimum refuelling interval at full rated output of not less than 4 hours for solid mineral fuel burning or 1.5 hours when burning wood. In addition, it must be able to “hold a fire” at low burning rate and be revived after no less than 12 hours for solid mineral fuel and 10 hours for wood logs. These appliances will suit people who don’t want to keep lighting their fire up from cold. They are used more as a primary source of heat.
Stoves are classed as ‘intermittent operation’ when refuelling intervals of 45 minutes or more are given to get the rated heat output on wood, or 1 hour or more to give the rated heat output on solid mineral fuel. These stoves are suitable for people who want to have a fire in the evening or want a secondary heat source to supplement their main system.
4. Dry or wet stove?
Dry systems are generally designed to provide heat directly into the room in which they are installed. The appliance is attatched to the property via a flue which leads out to the chimney.
Wet stoves have integral boilers which are attached to water tanks and generate part or all of the heat required for a household's hot water needs. Wet systems can be used in conjuction with solar power, using a stove for heating and hot water in the winter months and solar power in the summer.
5. Woodfuel, solid fuel or multi fuel stove?
A woodfuel stove is designed to run exclusively on firewood (or other solid biomass fuels). To get an efficient burn using logs, you should either buy seasoned logs from a reputable (or HETAS certified) supplier, or season them yourself for a period of up to two years. Firewood should be sheltered in an environment that has plenty of air flow, in order to help the wood dry effectively over time.
A solid mineral fuel stove is designed to run on fuels such as anthracite. A multifuel stove will run on either solid fuel or wood fuel. These appliances may burn woodfuels with a greater gross eficiency than solid mineral fuels and vice versa. If you are planning to buy a multifuel stove with the intention of running it primarily on one fuel, this is key.
6. Why would I need to buy a DEFRA approved stove
DEFRA approved stoves are essential for all people who wish to use an appliance to burn firewood or other non-authorised fuel in a smoke control area. These appliances are designed to restrict the environmental and health impact of chimney smoke where population density is great. Non-exempt stoves are restricted to burning only authorised smokeless fuels in these zones.
In the future you can look for HETAS Approved Retailers when looking for a stove. These showrooms will have trained staff, display advice sheets and label appliances with all the information that you need to make an informed choice.
About the author: Laurence Jones was marketing support officer at HETAS
If you have a question about anything in the above blog, please ask it in the comments section below.
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