Tuesday 10 December 2013

A New Log Burner

There is nothing prettier than an open wood fire but if you’re trying to be frugal it gives little comfort to know that 80 percent of the heat it produces disappears up the chimney. A wood burning stove is much more efficient and effective. For a start it acts more like a radiator than a fire. The heavy iron casing throws heat into the room and the huge chimney is reduced to a single small flue. The rest of the chimney can be sealed with insulation to keep heat in the building.

There was a wood burner here when we bought this house - a  ‘Vermont’ cast iron job putting out 8 Kwts of heat  and it was enough to keep the whole house cosy even during a hard winter.

But as a heater for a second home, a holiday home, it had a few drawbacks. Firstly, it took about a day and a half to reheat the fabric of the house, so if you came here for a long weekend, say arriving Friday afternoon, the house wouldn't feel really warm until Saturday night. Secondly, because the chimney wasn't used between visits and it hadn't been lined or capped, rain water came in.

One February night we arrived here, lit the stove and choked on the smoke which filled the room. Investigations the next morning turned up a dead pigeon and an owl in the flue. They had obviously fallen in there and died a horrible cold death. Soon after we had a ‘chapeau’ fitted to the top of the chimney to prevent further useless deaths – and to help keep out the rain.

But, by then the iron stove had rusted due to the rain and lack of use. Bits were beginning to fall off. A new stove was called for and it was one of the first improvements we made when we moved here permanently but if you’re thinking of getting a wood burner it is important that you do some thorough research into your needs and circumstances.

In France stoves are described according to the heat they put out – the measurement is in Kilowatts.  Now a stove is most efficient when she is burning good wood and when she is stacked reasonable well. It’s difficult to have a small fire in a stove so you need one that produces enough heat when burning efficiently – but not too much – otherwise you’ll be opening doors or running half empty which is not efficient.

To calculate what size stove you need, begin by obtaining the ‘volume’ of space you want to heat. Measure the width, length and height of your room and then multiply the three measurements together, i.e. width 8m x length 4m x height 2.8m = 89.6 cubic metres.

Now, if your house were a new build and fitted with very good insulation, you would divide this figure by 25. For a room with average to good insulation you would divide the volume by 15. If the insulation were poor or non existent, then the division of the room’s volume would be by 10.  If you are unsure use 15 to get an idea of the Killowatts you need.

Ok so that is the size of space you want to heat but if you've got an open staircase in your living room, heat will rise up it. This may be a good or bad thing, you may want the hot air to rise through the upstairs of the house – or you may prefer to insulate your room and use other solutions upstairs. Either way, just remember that heat rises and bear that in mind when you make your calculations. 

Another thing to know is that old stone houses like this one prefer a fairly constant level of heat and humidity so you need a stove that will bring the house up to your preferred temperature steadily and then maintain that temperature at an efficient burn.

Finally the size, type and quality of your wood matters.  Generally any dry hardwood will do but Oak is one of the most popular because it is very dense, it burns slow and hot, and it is easy to split. Birch also burns well but it burns fast. Poplar is popular as is Ash and Elm.
 Softwoods are not so good because they contain a significant amount of resin which can build up in the flue and, over time, you risk an uncontrolled blaze in the chimney or flue. The drier and more mature the wood the better. An easy test is to bang two pieces together; a dry mature log will have a musical note. In this part of France wood is sold by the Cord a cubic measure of neatly stacked logs 3M x Im  x Im. Three Steres make a Cord. I use about a Cord and a half each year at a cost of about 360E per year.

 Generally, in this part of France wood is sold as 30cm or 50cm logs. 30cm logs are more expensive because there is more wastage in sawdust. Now, ‘here is the rub’ as Shakespeare would say, our new log burner is an ‘Invictor’ which takes logs of 45cms! Bit of a pain really, either we pay more for smaller logs or I have to re-cut every log in my store!

If you have the space, you can save money by sourcing your own wood, cutting, storing and seasoning it yourself before it will be required, or  by purchasing cut  logs ‘green’, and seasoning as above but you need to get at least a year ahead (two years is better still) – purchasing or cutting, stacking and protecting now for 2015 or later.

Well, in France they say a log warms you up twice – once when you cut it and again later when you burn it, - but once you find a good woodman treat him as a family treasure.

If you are thinking of buying a log burning stove, there is a great deal to think about. I used this book and found it a great help in making a good choice

The Log Book: Getting the Best From Your Wood-Burning Stove, 2nd Edition (USA Readers)

the log book (UK Readers)


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