Having criticised a recent Guardian article ( see post for 5th January 2010 entitled, Wood Burning Stoves: The Truth? I dont think so ) I feel obliged to say a bit more about wood burning stoves. Over the years I have read several weekend supplement articles which skim the surface and so I thought it was time to write a more comprehensive piece. Wood burning stoves are not for everyone. They take a bit of work, wood supplies might not always be easily available and special care needs to be taken if you plan to buy a multi-fuel stove when you live in a smokeless zone. Having the option of burning coal can be seen as a comforting, but certainly not green, back up, should seasoned wood be in short supply.
Buying in wood fuels is no longer a cheap option as demand has increased considerably in recent years, but there is a lot of unmanaged woodland still in the UK and gradually this is being increased. Sadly you can still see ‘waste’ wood being burnt alongside roads and railways. Wood is no longer permitted as land fill but it is unclear where it now goes. There is a long way to go before woodland becomes threatened and in the meantime processed wood based fuels will become more widely available.
If you are wondering whether a wood burning stove might fit in with your energy requirements here is the story of our involvement with this method of heating. Whatever you do think long and hard about the costs and work out how you will keep it supplied with fuel.
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My first sighting of a wood burning stove was one of those box Jotol stoves which are designed to burn wood by slow combustion. Apart from some rather nice relief’s’ in the cast iron it was not much to look at, especially for someone raised in front of various open fires and glowing ranges. This was in the early seventies on our first visit to the Centre for Alternative Technology just after it had opened to the public.
From then on the number of models increased and our first stove was a Hunter Multi Fuel which we installed in a brand new house back in 1989. Unfortunately it was very difficult to get decent wood fuel and for much of the time we burnt Homefire ( coal briquettes) which we literally glimpsed through a glass darkly. It had a horizontal rectangular opening with two doors which made refuelling awkward and although it knocked out a good heat its drawbacks meant that when mains gas came through it was soon disposed of. We learnt a great deal from this experience and the open fire was still seen as a much more convenient means of warming the front room at grandma’s cottage in Hereford. Supplies of logs were easily available and we continued with the open fire when we took on the cottage in the early eighties.
Another reason for sticking with the open fire was that at the time the pollution was not much different between it and the wood burner. Take for example these claims from Conservation at Home: A Practical Handbook by Michael Allaby published in 1988,
‘Benjamin Franklin designed the prototype of the ‘modern’ wood burning stove...a stove like this may look beautiful, but environmentally it is a disaster. By burning wood very slowly with very little air, it produces a range of unburned hydrocarbons, many of which are known to cause cancer, together with carbon dioxide and carbon monoxide, all of which are released into the outside air along with radioactive potassium 40.’
The open fire in contrast threw a bit more ash into the atmosphere but since it used much more air some of the pollutants were burnt off. Both means of heating also produce sulphur dioxide but the open fire lets 90% of the heat go up the chimney whilst causing doors to swing open in the drafts needed to supply the necessary oxygen. So the question always being asked was whether the big outlay on a stove was worth it.
You can still find versions of Franklin’s original design for sale and they are still used to heat many mountain holiday log cabins in North American. When you can cut vast quantities of big logs from your holding they can still make sense if efficiency and pollution issues are ignored. For those of us who have to buy in the bulk of their wood it is not a practicable option but the Franklin has the great advantage of being able to turn from an open log fire into a closed cast iron cupboard for slow burning overnight.
After our experience in the seventies I remained very sceptical about wood burning stoves even though stove design had moved on from the old smouldering versions. But in 1989 I discovered a new system ( explained below) when visiting the Clearview Stoves small showroom in Ludlow. I had not really got the point at that stage but then a good friend of ours bought one and he started his proselytising. Then we came across another installation and then another. In the end we had seen five different installations and were impressed despite several conservation and environmental reservations.
The crunch came when I had to check out the TV aerial when we went digital. The open fire had not been lit the previous day so all was cool in the fireplace. At the top of the chimney it was a different story. Much to my surprise I found that there was a nice lot of warm air being emitted. Distressingly I soon realized that the bulk of this warm air was being extracted by the chimney in the form of the heat stored in the night storage heaters as supplemented by the Yorkist Stove in the kitchen. ( More on the Yorkist Stove in a later post) So that’s what they meant when they said up to 90% of the heat from an open fire escapes up the chimney! Even when its not burning any other heat you have paid for will be sucked up up and away. It so happened therefore that this was my ladder to Damascus and from then on Sian and I started to take the prospect of a wood burning stove much more seriously
Energy conservation now started to be set against pollution issues and the process of conversion continued. By chance we visited the Clearview Showroom in Ludlow, now occupying a small mansion, and we concluded that this was a very good product. However, still being sceptical we put a wood burner well down the list behind upgraded insulation and a solar panel. We were also put off by the cost and started to look at slightly cheaper options which would offer a multi-fuel grate just in case our wood supply proved unreliable. We soon found out that the Clearview didn’t need any special grate. It was multi-fuel anyway. Most importantly, Clearview make a lot of the fact that their stoves burn in a way which keeps the glass front door clean so that the log fire can be seen. Other manufacturers offer similar systems with varying degrees of success so I had better explain the basic idea.
With old style slow burning stoves much of the by-products remain un-burnt because of the lower temperatures involved. The idea behind many new stoves is that the drafts of hot air within the firebox are made to pass over the glass window and burn off any deposits which have not already been burnt by the high temperatures in the stove. Ideally this works best when well seasoned wood is being used and there is no back boiler to reduce the temperature in the fire box. As a result you will be able to see a flaming log fire while reducing pollutants. Designs which need less air to burn hot will also reduce drafts. In any case, with no open chimney effect more heat is kept in the house whether the stove is burning or not.
After lots of thought we ordered a Clearview as we had concluded that this was the stove of choice among our contacts and we had seen so many of them in action. Another important factor was that it was a local product. There is a bewildering choice now available and there is a very wide range of prices so do nothing in a hurry. My advice to anyone considering a purchase is to go and see as many stoves in operation as possible, preferably in the homes of people who know what is involved in running a stove. Some might not bother to season their wood properly so if there is a smoked up window this does not necessarily mean the stove is at fault.
Dry wood obviously burns better than damp wood. Its heat output is higher and heat is not wasted heating up the moisture in the wood which goes up the chimney as steam to condense there or go into the atmosphere. A stove run like this will not give a good result. The window will be black and no fire will be visible and tars will accumulate high in the chimney where the have condensed. This causes a fire hazard.
Provided the heat is maintained throughout the length of the flu the risk of soot build up is greatly reduced. This is why manufacturer’s and good suppliers stress the need for a well insulated flu. This is achieved by means of one of the lining systems on offer. Unfortunately this can often double the cost of an installation. Much depends on the kind of chimney already in use for an open fire.
The high temperature which creates a secondary burn should, it is claimed, reduce the amount of tar and thus some of the pollutants. Carbon dioxide is still given off, how much is still subject fo debate, but if the sources of your wood are from sustainable woodland it will be doing a good deal to re-absorb it and thus making the wood burner carbon neutral. For overnight burning in order to avoid the worst consequences of slow burning the trick is to make the fire up sometime before bed time and run the stove with a good deal of flame. This burns off many of the pollutants so that by the time the stove is shut down for the night the fire continues in the form of glowing ‘char coals’.
Organising your wood purchasing to have seasoned wood is essential. Ideally wood which has been seasoned for 2 years should be aimed for. It is now possible to buy a handy moisture meter to make sure the wood is at the right moisture content. The number of wood suppliers is increasing and if you can find a local supplier who runs a sustainable wood then your carbon footprint shrinks greatly and keeps some people in work within your local economy. If you have your own woodland then a major element is removed from the process and you will know exactly what you are burning.
Is it all worth it? In our case the answer is a resounding yes but this outcome has only been achieved by following the points above. The most important point is to get the right stove for you and make sure it is a modern model. Don’t be tempted to buy on price alone and make sure you take advice from as many independent people as possible. The biggest advantage in comfort terms is that a closed stove can almost eliminate drafts. If you are buying a stove with more than a 5kw output an airbrick is required by building regulations so make sure that this is placed as near to the fire as possible.
The next advantage is in the savings you make when you no longer lose 90% of your heat up the chimney. These results will come whether you burn coal or wood. If you burn wood you should be able to reduce your carbon footprint and the amount of pollution involved in keeping yourself warm. Where we live we don’t have a gas supply and we would not install oil or LPG central heating on principle and price. That leaves us with electricity which is inefficient in the loss of energy involved in getting it to us and, unless consumption is at night, can be very expensive. Consequently we have night storage heaters and a night running immersion heater. The washing machine, washing up machine and the bread maker are all run at night whenever possible.
The wood burning stove when all the above factors are taken into account has made a great difference to our comfort, our carbon footprint and our emissions and brought our electricity bill down. It is our top ‘green’ installation after our update of the insulation and the installation of our hot water solar panel and heat store water tank. There is still quite a lot more to do but we manage to keep quite cosy at a reasonable cost.
See earlier posts:
Further posts will appear on sustainable fuel supplies, solar panels, the Yorkist ( or York) Stove etc
Wednesday 3 February 2010
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