Wood fires: The cold evenings at the beginning of October caused us to have a fire in our wood burning stove in the lounge for several evenings running. Somewhat belatedly, I had a look up the chimney whilst relaying to fire ready to relight it later that day. It really ought to be swept, as it has not been swept before. After a phone call, it was arranged for a chimney sweep to clean the chimney in 5 weeks’ time. I should have organised this last summer!
Open fires are very inefficient, as most of the heat from the fire, and in the room, is drawn up the chimney and lost. Typical fuel efficiency for an open fire is around 10% of useful heat, compared to 80-90% for an efficient enclosed stove. Fires need an air supply, and it is more effective/efficient to supply the fire with air ducted from outside, instead of drawing air from the room. Air drawn from the room by the fire has to be replaced from air drawn into it as cold draughts.
The effectiveness of a wood fire is dependent on the type of wood, and how dry the wood is. Freshly felled ash contains about 35% moisture, whereas poplar wood can contain up to 60%. Trying to burn damp timber produces steam, and less heat as a result. Damp wood can also cause more smoke, and tar deposits in the chimney.
Timber should be stored in a ventilated area and under cover for at least 6 months to allow the timber to dry before being burnt.
Some of the best timbers for burning are ash, beech, hornbeam, hawthorn, apple and cherry. Oak and elm are dense timbers, but can be slow to burn. These two timbers are better burned as a mixture with other timbers. Spruce and horse chestnut woods tend to spit, so should not be used in open fires for this reason. Softwoods such as pine and spruce are easy to light, and burn quickly, so are best for starting a fire.
Supplies of wood can be found in adverts in “The Villager” magazine, or from the website www.bigbarn.co.uk/logpile.
A rough guide to the size of a stove is that a 5kW stove should be able to heat a room 2.4m high by 25 square metres floor area, but the insulation of walls, ceiling, and windows, plus draught proofing, and air supply, all have an influence on this estimate.
Information about wood burning stoves is available from: