Wood-burning stove
Encyclopedia
For a list of stove types see Stove (disambiguation)
.
A wood-burning stove is a heating appliance capable of burning wood fuel
and wood-derived biomass
fuel. Generally the appliance consists of a solid metal (usually cast iron
or steel
) closed fire chamber, a grate and an adjustable air control. The appliance will be connected to a suitable chimney or flue which will fill with hot combustion gases once the fuel is ignited. It is critical that the chimney or flue gases be hotter than the outside temperature as this will result in combustion gases being drawn out of the fire chamber and up the chimney.
and softwood
have the same energy content (by mass) and will provide similar energy outputs. However, the essential difference will be in the rate at which the fuel burns. Hardwoods derived from slow-growing broadleaf trees will burn at a slower rate for sustained output. Softwoods are derived from evergreen trees such as conifers, which are fast growing. They burn at a far greater rate. Another disadvantage of soft wood is it creates more soot and other deposits on the inside of the wood stove, chimney, and flue therefore causing more frequent cleanings.
. This can damage the chimney and spread fire to the surrounding structure.
For best results firewood should have a moisture content of less than 20%. The process of removing the excess moisture is called seasoning. Seasoning by air-drying the wood can take up to two years. Wood should be stored in an outdoor well-ventilated, but covered, structure. A recent innovation is kiln-dried wood. With interest and usage of wood burners at an all-time high, some companies are now using large kilns to quickly dry their wood.
Hardwood must be well-seasoned, with some species taking up to four years to dry out. Hardwood is seasoned by being left out to the elements for three to four winters, then for a subsequent summer under cover with ventilation to dry out. Softwood is left out to the elements for two winters, then for one summer to dry out with ventilation.
Modern building techniques have created tighter sealed homes, forcing many stove manufacturers to recommend their stoves be installed with outside air intake. Outside air ensures that stoves will run more efficiently, also removes the need for cold air for the combustion process to pass through the living space reducing "draughts" and improving comfort of the occupants. This design is called "room sealed stoves" or "external air supply stoves."
, local authorities may declare the whole or part of the district of the authority to be a smoke control area. It is an offence to emit smoke from a chimney of a building, from a furnace or from any fixed boiler if located in a designated smoke control area. It is also an offence to acquire an “unauthorized fuel” for use within a smoke control area unless it is used in an “exempt” appliance (“exempted” from the controls which generally apply in the smoke control area). The current maximum level of fine is £1,000 for each offence.
In order to comply with the Clean Air Act in "smoke control areas," an exempt appliance or fuel must be used.
requires that wood stoves and wood heating appliances be certified by the Environmental Protection Agency
(EPA). These devices meet a particulate emissions standard of no more than 7.5 grams per hour for noncatalytic wood stoves and 4.1 grams per hour for catalytic wood stoves. Washington State has stricter requirements of a maximum of 4.5 grams per hour.
is one of the biggest markets for wood-burning stoves in Europe, having around 30% of all homes using wood for some heat. This means about 5 million homes have a wood fuelled stove or cooker.
Stove (disambiguation)
-Types of stove:* Air-tight stove* Bamboo stove* Beverage-can stove* Biomass cook stove, a fuel efficient and environmentally aware cookstove* Buddy Burner* Electric stove* Franklin stove* Gas stove* Hobo stove* Kang bed-stove...
.
A wood-burning stove is a heating appliance capable of burning wood fuel
Wood fuel
Wood fuel is wood used as fuel. The burning of wood is currently the largest use of energy derived from a solid fuel biomass. Wood fuel can be used for cooking and heating, and occasionally for fueling steam engines and steam turbines that generate electricity. Wood fuel may be available as...
and wood-derived biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
fuel. Generally the appliance consists of a solid metal (usually cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...
or steel
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
) closed fire chamber, a grate and an adjustable air control. The appliance will be connected to a suitable chimney or flue which will fill with hot combustion gases once the fuel is ignited. It is critical that the chimney or flue gases be hotter than the outside temperature as this will result in combustion gases being drawn out of the fire chamber and up the chimney.
Fuel and operational considerations
Fuel type: Hardwood or softwood
Both hardwoodHardwood
Hardwood is wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood...
and softwood
Softwood
The term softwood is used to describe wood from trees that are known as gymnosperms.Conifers are an example. It may also be used to describe trees, which tend to be evergreen, notable exceptions being bald cypress and the larches....
have the same energy content (by mass) and will provide similar energy outputs. However, the essential difference will be in the rate at which the fuel burns. Hardwoods derived from slow-growing broadleaf trees will burn at a slower rate for sustained output. Softwoods are derived from evergreen trees such as conifers, which are fast growing. They burn at a far greater rate. Another disadvantage of soft wood is it creates more soot and other deposits on the inside of the wood stove, chimney, and flue therefore causing more frequent cleanings.
Moisture content
One of the most critical factors in wood burning is the moisture content of the wood, as any water in firewood has to be boiled off during the burning process. Freshly cut wood (known as green lumber) has a high moisture content. Green wood of ash trees contains 35% moisture and green poplar contains 65% moisture. Apart from producing very low heat outputs, the flame temperature is also reduced. This causes unburned creosote. Creosote leaves the wood burner as a gas and cools to a liquid in the chimney. This oily liquid coats the inside of the chimney and collects soot and other combustion particulates. It can build up and reduce the draft in the chimney. It can also be ignited by a subsequent Chimney fireChimney fire
A chimney fire is the combustion of residue deposits referred to as creosote, on the inner surfaces of chimney tiles, flue liners, stove pipes, etc. The process begins with the incomplete combustion of fuel in the attached appliance, usually a wood or coal stove...
. This can damage the chimney and spread fire to the surrounding structure.
For best results firewood should have a moisture content of less than 20%. The process of removing the excess moisture is called seasoning. Seasoning by air-drying the wood can take up to two years. Wood should be stored in an outdoor well-ventilated, but covered, structure. A recent innovation is kiln-dried wood. With interest and usage of wood burners at an all-time high, some companies are now using large kilns to quickly dry their wood.
Hardwood must be well-seasoned, with some species taking up to four years to dry out. Hardwood is seasoned by being left out to the elements for three to four winters, then for a subsequent summer under cover with ventilation to dry out. Softwood is left out to the elements for two winters, then for one summer to dry out with ventilation.
Air supply
High heating efficiencies on closed appliances can only be attained by controlling the supply of air to the fire chamber (operating the air control correctly). It is not recommended to leave the air control fully open, except when helping the chimney/flue heat up initially. A fully open air control will lead to more heat being sent straight up the chimney rather than into the room (which reduces efficiency). The biggest problem with leaving the air control fully open is “overfiring”. Overfiring is caused when too much heat is generated within the fire chamber, which will lead to warping, buckling and general damage to the stove and its internal components. Individual stoves will have their own quirks, so take a little time to get used to a new stove's settings.Modern building techniques have created tighter sealed homes, forcing many stove manufacturers to recommend their stoves be installed with outside air intake. Outside air ensures that stoves will run more efficiently, also removes the need for cold air for the combustion process to pass through the living space reducing "draughts" and improving comfort of the occupants. This design is called "room sealed stoves" or "external air supply stoves."
Safety
Correct air flow and ventilation is also critical to efficient and safe wood burning. Specific requirements will be laid down by the stove manufacturer. Legal requirements for new installations in the UK can be found in Building Regulations Approved Document J, Section 2, Table 1 "Air Supply to solid fuel appliances"UK Smoke Control Areas
Under the United Kingdom's Clean Air ActClean Air Act
A Clean Air Act is one of a number of pieces of legislation relating to the reduction of airborne contaminants, smog and air pollution in general. The use by governments to enforce clean air standards has contributed to an improvement in human health and longer life spans...
, local authorities may declare the whole or part of the district of the authority to be a smoke control area. It is an offence to emit smoke from a chimney of a building, from a furnace or from any fixed boiler if located in a designated smoke control area. It is also an offence to acquire an “unauthorized fuel” for use within a smoke control area unless it is used in an “exempt” appliance (“exempted” from the controls which generally apply in the smoke control area). The current maximum level of fine is £1,000 for each offence.
In order to comply with the Clean Air Act in "smoke control areas," an exempt appliance or fuel must be used.
US pollution control requirements
The United States Clean Air ActClean Air Act (United States)
The Clean Air Act is a United States federal law enacted by Congress, and signed by President Richard Nixon on December 31, 1970 to control air pollution on a national level. It requires the Environmental Protection Agency to develop and enforce regulations to protect the general public from...
requires that wood stoves and wood heating appliances be certified by the Environmental Protection Agency
United States Environmental Protection Agency
The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...
(EPA). These devices meet a particulate emissions standard of no more than 7.5 grams per hour for noncatalytic wood stoves and 4.1 grams per hour for catalytic wood stoves. Washington State has stricter requirements of a maximum of 4.5 grams per hour.
Use in Europe
ItalyItaly
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
is one of the biggest markets for wood-burning stoves in Europe, having around 30% of all homes using wood for some heat. This means about 5 million homes have a wood fuelled stove or cooker.
Types
- Franklin stoveFranklin stoveThe Franklin stove is a metal-lined fireplace named after its inventor, Benjamin Franklin. It was invented in 1741.L.W. Labaree, W. Bell, W.B. Willcox, et al., eds., The Papers of Benjamin Franklin , vol. 2, page 419...
, invented by Benjamin FranklinBenjamin FranklinDr. Benjamin Franklin was one of the Founding Fathers of the United States. A noted polymath, Franklin was a leading author, printer, political theorist, politician, postmaster, scientist, musician, inventor, satirist, civic activist, statesman, and diplomat...
, is a more efficient type of wood-burning stove. - Carl Johan CronstedtCarl Johan CronstedtCarl Johan Cronstedt was a Swedish architect, inventor, Earl, noble, civil servant, scientist and bibliophile.-Biography:Cronstedt was the son of Jakob Cronstedt and Margareta Beata Grundel born in 1709 in Stockholm, Sweden. He married Countess Eva Margareta Lagerberg in 1744.Cronstedt became a...
is reported to have increased efficiency of wood-burning stoves by a factor of eight in the mid-18th century. - A Fireplace insertFireplace insertInvented in 1869 by Joab R. Donaldson of Oliphant Furnace, Pennsylvania, USA. The fireplace insert is a device inserted into an existing masonry or prefabricated wood fireplace....
converts a wood burning fireplace to a wood burning stove. A fireplace insert is a self-contained unit that sits inside the existing fireplace and chimney. They produce less smoke and require less wood than traditional fireplaces. Fireplace inserts come in different sizes for large or small homes. - Down draft or cross draft gasification stoves, i.e. Dunsley Yorkshire, Welkom 600, Avalon Arbor™ wood stove, XEOOS.
- Boiler Stoves provide hot water as well as space heating. A backboiler can be an optional insert added to the back of the firebox, or a wrap around water jacket that is an integral to the stoves structure. The choice determines how much of the stoves output goes to space heating vs heating water.
See also
- Red Cross stoveRed Cross stoveThe Red Cross stove is a kitchen stove used for cooking and heating a home of the late 19th and early 20th-century. The reason for the name "Red Cross" was because of the advertising logo used in promoting the product, which had a red Gothic cross.-History:...
- Air-tight stove
- Franklin stoveFranklin stoveThe Franklin stove is a metal-lined fireplace named after its inventor, Benjamin Franklin. It was invented in 1741.L.W. Labaree, W. Bell, W.B. Willcox, et al., eds., The Papers of Benjamin Franklin , vol. 2, page 419...
- Pellet stovePellet stoveA pellet stove is a stove that burns compressed wood or biomass pellets to create a source of heat for residential and sometimes industrial spaces...
- Reverse-process stoveReverse-process stoveThe reverse-process indoor wood burning stove is a non-catalytic airtight heater. Employing a unique reverse process whereby it not only draws exterior air in to the wood stove for combustion, thus eliminating interior drafts, it also releases fresh outside air into the room through a rear-mounted...
- Rocket stoveRocket stoveA rocket stove is an innovative clean and efficient cooking stove using small diameter wood fuel which is burned in simple high-temperature combustion chamber containing an insulated vertical chimney which ensures complete combustion prior to the flames reaching the cooking surface. The principles...
- Daruma stove - Japanese Traditional Wood stove
- Bukhari (heater)Bukhari (heater)A bukhāri is a traditional space heater from the northern areas of the Indian subcontinent, which is typically a wood-burning stove. Bukharis consist of a wide cylindrical fire-chamber at the base in which wood, charcoal or other fuel is burned and a narrower cylinder on the top that helps in...
, traditional Indian wood stove - Masonry stoveMasonry heaterA masonry heater is a device for warming a home that captures the heat from periodic burning of fuels , and then radiates that heat over a long period at a fairly constant temperature. The technology exists in many forms from the Roman hypocaust to the Austrian/German kachelofen...
External links
- The Solid Fuel Association Woodburning stove section
- UK Government-sponsored Biomass fuel website
- At "Wood stove & energy" is a free online tool available to calculate the heating power of different types of wood at differently moisture contents.