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wood stoves

Wood stoves are one of the most compact and useful forms of renewable power that you can incorporate into a house, and allows you to shift your dependency away from fossil fuels, even in built-up areas (assuming you don't live in a smoke-free zone). The woodstoves that we supply are very high efficiency, employing a unique pre-heated air feed (sometimes referred to as 'tertiary air') - a feature shared by very few woodstoves. Navitron supplies the complete range of chimney liners (flexible and sectional), boilers (from 6000 BTU to 35 000BTU) and other wood stove accessories, although not all of these products are listed on the website - please call for more information. We are looking at new products, which we intend to add to our range in the near future - such as log boilers and pellet stoves.

 

Background

 

Wood is one of the oldest heat sources known to man, and has been used since the dawn of time. In the early 1700s, a most remarkable scientist and inventor, Benjamin Franklin (most famous for his discovery of electricity), realised that open fireplaces were smokey, inefficient, and ran the risk of setting homes on fire from sparks. He set about designing the very first wood stove - it used 4 times less wood and generated twice as much heat - a remarkable improvement! This improvement was due to reducing the airflow through the fire. This allowed higher temperatures, which caused the smoke (unburnt distillation products of the fire) to burn - providing higher efficiency and less smoke. It also reduced the amount of air drawn out of the house by the fire.

 

Efficiency of open fires

 

The chimney effect caused by an open fire draws massive amounts of warm out out of the house - which means that an open fire has exceeding low efficiency. Studies in the USA have demonstrated that open fires have efficiencies of minus 15% to plus 10%. Yes, they can actually make your house colder!! The heat of the fire may convince you that the house is warmer, but large quantities of warm air are sucked up the chimney, to be replaced by cold air from outside. There is no doubt that open fires are polluting and low efficiency, and their use should be banned in the UK.

 

Efficiency of Wood Stoves

 

Wood stoves are very efficient. Most woodstoves are around 85% efficient, with very little heat lost through the chimney. They are not quite as efficient as a modern condensing central heating boiler, but they have zero carbon footprint, as any carbon dioxide produced by a woodstove is simply reemitting carbon dioxide absorbed by trees during their lifetime. As long as the wood is from a sustainable wood source, there is no net increase in CO2 emission - making woodstoves a very environmentally-friendly heat source.

 

Exhaust emissions

 

People often associate wood fires with a lot of smoke, and certainly this is the case with open fires. Older woodstoves can produce a certain amount of smoke under certain conditions, but significant improvements have been made over the last decade in terms of smoke emission. Further improvements can be made by preheating the input air to the stove. Very few manufacturers have achieved this in their design, but the Fireview stoves offered by Navitron are considered the best available on the market in this respect. If the air entering the stove is preheated to 400F by passing the air through long preheat channels in the top of the stove, it will cause spontaneous combustion of any smoke - even if it is produced by wood that has just been added to the fire.

 

Wood               Characteristics                                                                                                                            Grade

 

Alder                 A low quality firewood                                                                                                                    1

 

Apple                Needs to be seasoned well. Burns well with a pleasant smell and without sparking/spitting.               3

 

Ash                  Considered to be one of the best woods for firewood. It has a low water content (approx.              4

                        50%) and can be split very easily with an axe. It can be burned green but like all wood is

                        best when seasoned. Burns at a steady rate and not too fast.

 

Beech               Beech has a high water content (approx. 90%) so only burns well when seasoned well.                  3

 

Birch                 Birch is an excellent firewood and will burn unseasoned. However, it does burn very fast                 3-4

                        so is best mixed with slower burning wood such as Elm or Oak.

 

Cedar               A good firewood which burns well with a pleasant smell. Gives off a good, lasting heat.                     2

                        Doesn't spit too much and small pieces can be burned unseasoned

 

Cherry              Needs to be seasoned well. Burns well with a pleasant smell and without spitting.                             2-3

 

Elm                   A good firewood but due to its high water content of approximately 140% (more                          2-3

                        water than wood!) it must be seasoned very well. It may need assistance from

                        another faster burning wood such as Birch to keep it burning well. However it gives

                        off a good, lasting heat and burns very slowly. Dutch Elm Disease is producing a

                        constant & plentiful supply of small dead hedgerow Elm trees of a small diameter.

                        Larger pieces of wood will prove difficult to split.

 

Eucalyptus       Allow to season well since the wood is very wet (sappy) when fresh. Can be difficult                         2-3

                        to split due to stringy wood fibre. Best method is to slice into rings and allow to season

                        during the summer, the rings will start to split themselves. Burns fast with a pleasant

                        smell and without spitting.

 

Hawthorn         Good firewood. Burns well                                                                                                               3-4

 

Hazel                Excellent firewood. Allow to season. Burns fast but without spitting                                                  4

 

Holly                 Can be burnt green. A good firewood                                                                                             3

 

Hornbeam        Good firewood. Burns well                                                                                                               3

 

Horse                A low quality firewood                                                                                                                     2

Chestnut

 

Larch                Needs to be seasoned well. Spits excessively while it burns and forms an oily soot within                  1

                        chimney's.

 

Lime                 A low quality firewood                                                                                                                      2

 

Oak                  One of the best firewood's. When seasoned well, it gives off a good, lasting heat.                            4

                        Burns reasonably slowly.

 

Pear                 Needs to be seasoned well. Burns well with a pleasant smell and without spitting.                              3

 

Pine                  Needs to be seasoned well. Spits while it burns and forms an oily soot within chimney's.                  1

 

Plane                A usable firewood                                                                                                                           3

 

Poplar              Considered a poorer firewood (see comments below)                                                                      1

 

Rowan             Good firewood.                                                                                                                               3

 

Spruce            A low quality firewood                                                                                                                      2

 

Sweet             Burns when seasoned but spits continuously and excessively. Not for use on an open fire                1-2

Chestnut        and make sure wood-burning stoves have a good door catch

 

Sycamore       Good firewood. Burns well                                                                                                                3

(Maples)

 

Walnut            A low quality firewood                                                                                                                      2

 

Wellingtonia     Poor for use as a firewood.                                                                                                              1

 

Willow             Willow has a high water content so only burns well when seasoned well                                             2

 

Yew                A usable firewood                                                                                                                             2-3

 

 

 

How to Burn Wood in your Woodburning Stove / Woodburner

 

The most appropriate fuels are seasoned, cleaved hardwoods. Coal is most appropriate when slow burning is required. It is not appropriate to use the following as fuel: wet, tarred, treated or painted wood; sawdust or wood shavings; fine coal, paper or cardboard (except when lighting).

 

1. Burning Wood.

 

Wood should be cut, split and then stored under cover with sides open to the air for at least a year. (It takes two years for some hardwoods to season fully.) Store it inside the house for a few days, or in the warm log store for a few hours before it is actually used in the woodburner.

 

Wood that is too wet will not burn properly and will give off little heat. Heat from the fire will be lost as it is used to evaporate the water vapour from the wood. It will cause excessive pollution and darken the glass.

 

When refueling, place wood towards the back of the stove where it will burn hotter and more efficiently. Try to place logs length ways so that any spitting from the end grain does not go onto the glass window.

 

2. Types and Characteristics of Wood

 

The quality of firewood is based upon various characteristics such as its speed of burn, heat given off, tendency to spark (spit), ease of splitting, time required to season, etc

 

Grade: 1 = Poor

Grade: 2 = Low

Grade: 3 = Good

Grade: 4 = High.

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