Everything you need to know about wood-burning stoves
What is a wood-burning stove?
In the United Kingdom a wood-burning stove is also called a wood burner or log burner. The name is sometimes used synonymously with wood-burning fireplaces.
A wood-burning stove can be a free-standing or built-in appliance of varying sizes that uses wood, or wood-derived fuel, such as compressed sawdust bricks or wood pellets, to generate heat for a home, apartment, single room, or large areas.
Some wood-burning stoves are specifically designed to provide heat outdoors. Advanced wood-burning stoves have also been specially developed for heating hot tubs, saunas, boilers and for cooking purposes.
Top-quality wood-burning stoves are manufactured from cast-iron or solid high-quality steel. Some of the most esteemed manufacturers include Chesney’s, Morso, Stovax, Rocal, Vogelsang and Esse. Quality wood burning stoves such as these will easily last for generations to come.
The first wood-burning stove was patented in the 16th century in Strasbourg. However, 21st century wood-burning stoves designed and built using advanced technology, bear little resemblance to those early models, except perhaps for retro design-styling of some models.
An advanced modern wood-burning stove is ventilated by specially designed flues that enhance the burning efficiency of the stove, draw fresh air from outside for combustion, prevent backdrafts into the room, and expel the low level of unburnt gases safely into the atmosphere. (Please see further explanations on chimneys and flues.)
What is a good quality cast-iron wood-burning stove?
Cast-iron is a material consisting of iron, mixed with carbon and small amounts of silicon, manganese, sulphur and phosphorous. Various amounts of nickel, chromium and molybdenum may also be included in the best quality cast-iron to make it more resistant to heat, rust, wear and corrosion.
Cast-iron is imminently suitable for building high-quality wood-burning stoves exactly because it is so strong, hard-wearing, highly heat resistant, and it does not rust or corrode easily. Cast-iron retains the heat energy well and transfers it evenly to the air around it.
The cast-iron is produced in a special process under extremely high heat and all impurities are burnt off. The raw material is then melted and cast into moulds to obtain the desired form or shape, hence the name.
The quality of cast-iron varies greatly and it is prudent to research reputable stoves and brand names to ensure the product is made from top grade cast-iron. At the highest end of the market, the cast iron components are inspected for pits, cracks, and rust before, during and after assembly of the stove. Once assembled, the stove is inspected to ensure that the stove is airtight to prevent smoke from escaping from the body of the stove rather than moving through the flues. As a final test for cracks, it is inspected to see if any oil seeps through the metal, when the stove is oiled to prevent rusting.
At the lower end of wood-burning stoves, inferior cast-iron might be used or may contain as little as one-third cast-iron. Called “pig-iron” at that stage, some of the cast-iron may contain high quantities of scrap metal for volume, which diminishes the quality.
What is a good quality steel wood-burning stove?
At the top end of the market, specialised wood-burning stoves will be manufactured from the best quality steel, consisting of a mixture of various amounts of iron, carbon, manganese, silicon, aluminium, nickel, chromium, cobalt, molybdenum, vanadium, tungsten, titanium, niobium, zirconium, nitrogen, sulphur, copper, boron, lead, tellurium, and selenium.
Sometimes wood-burning stoves are manufactured from stainless steel. Again, it is necessary to evaluate the quality and thickness of the steel used for the particular appliance. Remember, you get what you pay for.
What is the difference between the advanced modern wood-burning stoves and those of even a few decades ago?
Efficiency and safety
Particularly in the past few decades, manufacturers of wood-burning stoves have had to comply with very stringent environmental laws and building regulations.
Modern homes are much better insulated than in the past and toxic gases are sealed in. People have become much more safety conscious and demand strict adherence to health and safety considerations. We have become a lot more responsible in our environmental management approach and air pollution has become unacceptable.
Thanks to advanced technology, these challenges have been met and modern wood-burning stoves have become much more energy efficient, using about a third of the fuel required in older models; are much more eco-friendly, burning much cleaner; are much safer to use; and their heat output is an enormous eight times more than for an open fireplace.
Some of the technology employed in modern wood-burning stoves include catalytic converters or other clean-burn technology, air-wash technology, secondary combustion chambers, forced-air intake and airflow, ceramic glass windows to safely contain the fire without impeding the view of the flames and more. The technology used in modern flue systems are very far ahead of the old concept of a chimney through which most of the heat escaped and had to be cleaned constantly. (Please see further explanation under flue systems and chimneys.)
Aesthetics have not lagged behind either. The range of architectural and artistic designs are almost endless, with the emphasis on visibility of the flames. Wood-burning stoves have been developed to match any décor from traditional, period, contemporary to ultra-modern. Some are available in a variety of colours.
Modern wood-burning stoves are much more versatile than older models. There are models designed to be built-in; models to be inserted into existing fireplaces; free-standing models that can be installed against a wall, suspended from the ceiling, installed on a solid or swivel base; there are models that can be installed in the middle of the floor; and there are even models with dual openings that can be installed between rooms.
What is a Catalytic Wood-Burning Stove?
Modern wood-burning stoves are built in many different ways, but the premier type stoves are typically divided into two categories, catalytic and non-catalytic stoves.
Catalytic stoves are equipped with a catalytic combustor, that works much like the catalytic convertor used in motor vehicles, to reduce pollutants by burning off virtually all the gasses and particles that are vaporised in the first combustion. The catalytic combustor is constructed like a honeycomb matrix, from steel or ceramics, which is then coated with a catalyst like platinum or palladium.
The smoky exhaust from the first combustion is forced through the catalytic convertor where it is reignited at a much lower temperature than is normally required. On average, it requires a temperature of 600 degrees Celsius or higher to set those gasses and particles alight. The catalytic combustor makes it possible to burn theses gases at almost half that temperature, in other words slightly higher than 300 degrees Celsius.
Because virtually all the gasses and particles emitted the first time, are now burnt off in a secondary combustion chamber, at the same time as the wood is burnt in the primary combustion chamber, the fire requires less fuel, burns slower and longer, and emits hardly any pollutants. Typically, a good catalytic stove will emit 4.1 grams of smoke, or less, per hour.
Heat is generated more evenly and steadily. The process also allows stoves to be regulated to achieve lower heat output, which is highly desirable when a fire is required for ambience in slightly warmer weather.
Catalytic combustors require some maintenance to keep them clean and the airflow unobstructed and the catalysts have to be replaced every few years.
Non-Catalytic Wood-Burning Stoves
Modern non-catalytic stoves are also equipped with secondary combustion chambers to burn the unburnt gasses and particles release in the primary burning process for a second time, but do not use catalysts. However, these stoves require a much higher temperature to achieve the secondary combustion process. This means they are very effective at higher temperatures, but less so at lower temperatures.
Non-catalytic combustion stoves reduce emissions by using interior baffles which create a longer flow path for the hot exhaust. This allows more time for the gasses and particles to burn off and therefore emit fewer pollutants.
Hybrid stoves have been developed that employ both catalytic and non-catalytic secondary combustion. At lower temperatures, the catalytic combustor does the work, while the non-catalytic combustor takes over at higher burning temperatures.
There are still stoves at the lower end of the market that do not employ any secondary combustion. They are markedly less efficient than their upmarket counterparts and may not be used in smoke-controlled areas. Typically, non-catalytic stoves produce 7.5 grams or less of smoke per hour.
What parts are used to build an advanced modern wood-burning stove?
Wood-burning stoves do not have many moving parts that can wear out, but they are exposed to high heat. To keep your stove working properly and safely for decades, you just need to understand the various parts and how to treat and properly maintain them.
You build your fire in the firebox. Sometimes a grate is installed in the firebox, but in other models the fire is built on the floor of the firebox. A firebox can be lined with various materials such as cast-iron panels, steel, stainless steel, refractory cement or firebricks for better insulation and heat radiation.
The firebox will have a loading door to allow access to build the fire and add wood as the fire burns. Apart from the fact that they keep the wood from falling out, the door requires a tight seal to ensure the fire will heat up the stove and no smoke escapes.
It is necessary to perform regular maintenance on the hinges, seals and handles. This is essential at the beginning of winter and at regular intervals to ensure trouble-free heating of your home.
Good quality handles are important to prevent you from getting burnt when you open and close the door, and they should be solid enough not to come off in your hand at a crucial moment.
The best quality wood-burning stoves are equipped with ceramic glass windows that are heat resistant and allow you unimpeded views of your fire. Some models have a window in front, while others will have windows on two or even three sides for a panoramic view of the dancing flames and enhance the design qualities of the stove.
Air-wash technology keeps the windows clean and clear. The air-wash focuses combustion airflow and combustion along the top or bottom of the glass to reduce condensation of smoke and to keep the glass clean.
Air and Heat Control
All wood-burning stoves have some form of air control dial, handle or lever, to control the air intake and regulate the heat output.
In modern flue systems, the air flows from the outside to feed the flames without any of the cold air entering the room. This system keeps the oxygen levels in the room stable because it does not absorb oxygen from inside the house.
A baffle at the top of the firebox changes the direction of gasses in the stove, decrease them, slows them down for the fuel to burn slower and more completely.
Baffles can be made of cast-iron, steel, stainless steel, or brick.
A blower fan or circulating fan in some models works almost like a furnace to keep the flames burning brightly. It also helps distribute heat more evenly around the room.
A fan works with electricity and therefore should be inspected regularly to ensure the heat has not damaged the wires or the fan. They also have to be kept clean and oiled regularly to ensure effective operation.
Chimney and flue
This is an integral part of a wood-burning stove to ensure that harmful gasses escape, while heat is kept in the room.
- Flue collar – The opening at the top, back, or side of the stove requires a good quality collar to connect it safely to the flue pipes.
- Flue pipes – A variety of advanced flue systems, with single or double walls have been developed. Some flue systems have single or double skin liners to protect them and to improve efficiency. All connections should be airtight to prevent smoke from escaping.
- Flue pipes are made of different materials, but mainly from stainless steel, steel, ceramic, masonry, vitreous enamel, concrete, pumice or clay. It is of the utmost importance that the correct flue system is selected for its particular purpose and that for wood-burning stoves they are made of the best quality materials and lined where appropriate.
- The best stainless steel systems consist of two concentric stainless steel metal walls with insulation filling the annular space between them. Some systems have a ceramic liner, which can offer better insulation and a longer life.
- Flues have been designed to keep the heat in the room, while expelling all harmful gasses. The best flue systems allow for warm air around the escaping smoke, to ensure there is no downdraught to draw the smoke or gases back into the room.
- The best systems also allow separate compartments through which fresh air is drawn into the stove to feed the flames, without any of the cold air getting into the room.
- The best quality flue systems do not easily clog up with creosote and other contaminants and do not have to be cleaned as often as conventional chimneys.
- Some stoves are designed with dual flue systems.
- Modern flue systems also allow flue pipes from more than one stove to be channelled through the same chimney.
Please see further explanations on chimneys and flues
A damper is a movable plate to regulate the flow of gasses through the stove. In older stoves the damper was a round valve that was installed in the stovepipe. Modern stoves have a bypass damper that allows gasses and smoke to force the smoke and gases into the secondary combustion chamber or catalytic combustor when it is closed, or to bypass these chambers when it is open.
Some of the non-catalytic stoves are designed without a damper.
Secondary Combustion Chamber
Some stoves have a separate combustion chamber to allow the unburnt gases to burn for a second time, simultaneously with the primary combustion, to ensure cleaner burning and more efficient heat output.
Secondary Burn Tubes
Some wood-burning stoves are designed with perforated metal tubes at the top of the firebox. Combustion air flows into the firebox through these tubes and unburnt gasses that rise, mix with the oxygen in the tubes to reignite inside the firebox and burn for a second time, converting the unburnt gasses to heat energy.
This results in better heat output and cleaner emission into the atmosphere.
A catalytic combustor is a ceramic matrix panel system that looks like a honey comb, with numerous small channels and tubes running through it. Coated with a catalytic chemical such as platinum or palladium, it reduces the ignition temperature of the smoke passing through it, causing the smoke to burn at lower temperatures. This secondary combustion process burns away almost all the combustible gases, converting unburnt gas to heat energy, with very little smoke scaping through the chimney.
The ash pan located under the firebox, used to collect ashes and make it easier to clean the stove.
The area in front or around the wood-burning stove is called the outer hearth or hearth extension. The hearth is usually tiled or bricked to reduce the risk of fire and to protect flooring or furniture near the stove.
How efficient is a wood-burning stove?
The best manufacturers have designed modern wood-burning stoves to be remarkably efficient. Advanced modern stoves use only a third of the fuel to produce the same heat and are about eight times more efficient than an open fireplace.
They retain up to 90% of the heat generated by the fuel and only 10-15% percent of the heat escapes through the chimney and walls. The emissions of harmful gasses into the atmosphere is extremely low and none is released into the home.
In the UK, all the advanced-technology premier stoves are manufactured to DEFRA (Department for Environment, Food and Rural Affairs) standards and the stipulations of the Clean Air Act. A stove with DEFRA approval may be used in smoke-controlled areas, provided they are installed by HETAS (Heating Equipment Testing and Approval Scheme) registered installers.
Compliance with these requirements not only ensures compliance with legislation, it is your assurance of greater heat output, greater fuel efficiency and less air pollution. These technologically advanced stoves feature:
- External air intake to feed the flames, without any of the cold air entering the room.
- The external air-intake maintains the oxygen levels in the room, because the combustion air is not drawn from inside the house.
- Secondary combustion chambers, where unburnt gases and particles are mixed with oxygen-rich air to reignite them and burn the smoke for a second time. The secondary burning takes place at the same time as the primary burning, converting theses gases and unburnt particles to heat and saving fuel. Virtually all the gases, creosote and particles are burnt away, leaving much cleaner air.
- Advanced toves with catalytic combustors force the air through a honey comb of ceramic layers, which are coated with a catalytic material such as platinum or palladium. This causes the smoke to reignite and burn up virtually all the gases and particles, but at a much lower temperature than what would normally be required. Normally, it would require temperatures of about 600 degrees Celsius to set these gasses alight, but in a stove with a catalytic converter, this can be achieved at about half this temperature.
- This makes for highly efficient secondary burning, producing much longer burning and heat is generated more evenly. These stoves use less fuel and emit very low levels of smoke and creosote.
- Top of the range non-catalytic stoves make use of secondary burning chambers and internal baffles to reduce pollution and ensure effective combustion and fuel economy.
- Advanced flue systems that keep the heat inside the house, prevent downdraughts of cold air which will suck the smoke back into the room, and draw in fresh air from outside the house to feed the flames.
- In the best models of both catalytic and non-catalytic stoves, smoke emission is limited to between 4.1 and 7.5 grams of smoke per hour.
How effectively does a wood-burning stove heat the room?
The fire inside a wood-burning stove heats up the stove itself and the heat is radiated into the air around it. Via natural convection, electric fans, or convection fans, the heat is distributed to the rest of the room and ultimately to the rest of the house.
Some wood-burning stoves have convection chambers that draw in the cold air from the room, heat that air and then release it back into the room, thereby circulating the warm air, without depleting oxygen levels in the room.
Some models have convection pipes, heating the air in the pipes to transfer heat throughout the room, or even to adjacent rooms.
Warm air is less dense than colder air and naturally rises. This in itself causes convection that spreads the heat throughout the room and in particular carries it to the higher floors in the house, heating the upstairs parts.
Location of the heating stove is of crucial importance to ensure the best and most even distribution of the heat throughout the room and throughout the house. Good insulation is of the utmost importance to derive the best benefit of heating the house by means of a wood-burning stove. Draughty areas or passages, and installing the stove too close to staircases should be avoided. It is often best to avoid external walls, to keep all the heat inside the house’s “envelope.”
If a wood-burning stove is used in conjunction with central heating, the thermostat on your home’s central heating system can be turned right down to save expenses. Specific zones are heated by the wood-burning stove and the “excess” heat that spreads to other rooms and upstairs will help to warm the rest of the house.
Wood-burning stoves have been developed that can be placed between two rooms, with access from both sides, using the same amount of fuel.
How is a wood-burning stove’s heating capacity measured?
Typically, the heat output is measured in “British Thermal Units” (BTU) or expressed in (Kw), which is the equivalent of measuring the heat consumption and output of electrical devices.
This measurement is used to determine the size of wood-burning stove that is required to heat the specific room or space for which you require it. Naturally, a stove that has too little heat output cannot do its job efficiently. It is however not a good idea to install a stove of which the heat output is too high either. This will make it difficult to regulate the heat and will lead to wastage of fuel. The experts at Firehouse will give you the best advice and help you calculate the size of stove that is perfect for your requirements.
Firehouse sells and professionally installs all sizes of wood-burning stoves, rated from 4Kw to a massive 15 Kw output. Multifuel stoves, burning even hotter, are also available.
Do modern stoves emit any smoke or Carbon Dioxide?
Not all wood-burning stoves are of the same quality. At the top-end of the scale with both catalytic and non-catalytic stoves like Chesney’s, Morso, Rocal, Stovax, Esse and Vogelsang, you will have stoves that burn fuel cleanly, with very little smoke or unburnt gases released into the atmosphere and none into the room. (insert links to product pages)
It is also important to burn well-seasoned wood, or good quality wood-fuel derivatives like wood pellets or compacted sawdust bricks.
Is a wood-burning stove safe to use?
Health and safety are major concerns in advanced modern wood-burning stoves and they have been designed and built to meet the most stringent requirements. The premier stoves all meet the legal requirements of DEFRA (Department of Environmental, Food and Rural Affairs), the Clean Air Act and the Building Regulations. These manufacturers also insist that their stoves should be installed by qualified technicians who are approved and registered by HETAS (Heating Equipment Testing and Approval Scheme.) Some manufacturers set their own standards that exceed the requirements laid down by law to achieve an even higher standard of safety.
Correct air flow and ventilation
To achieve safe and efficient wood burning, requires correct air flow and ventilation. The design of the premier stoves and flue systems ensure that the air flows correctly and that no smoke can escape into the room from either the stove or any of the connections.
Modern flue systems also make provision for external air intake to make sure the oxygen supply in the room is not depleted, without any of the cold air entering the room. The design further ensures that the air is warmed around the smoke being expelled, to ensure there is no downdraught to draw the smoke back into the room.
Cleaning the flue pipes and firebox is essential to ensure there are no obstructions impeding the flow of air or smoke. In catalytic stoves the catalytic combustor must be cleaned every few months, and the internal baffles must be cleaned in non-catalytic stoves. The flues must also be cleaned to remove any build-up of creosote and soot. Not only do these build-ups impede the flow of air and smoke, they also lead to deterioration of the pipes. It is recommended that specialists are called in to do the cleaning.
The heat output is regulated mainly by controlling the fire, by increasing or reducing the air intake. One of the side-effects of reducing oxygen intake, is that carbon dioxide is converted to carbon monoxide, which is highly poisonous.
Keeping the flow of air and smoke unimpeded by installing the correct flues and maintaining them properly is crucial. It is also imperative that carbon monoxide detectors or alarms are installed for additional safety. Remember that not all smoke detectors detect carbon monoxide.
Only safe fire-starters should be used. Any accelerants like petrol, grease, oil, paraffin, plastics and so on, must be avoided at all cost. Apart from the pollution they cause, the flames can easily get out of hand and either spread into the room while the door is open, or overwhelm the firebox and flue system to cause a fire in the house or roof.
Even the best wood-burning stoves emit some pollutants. It is very important to use the correct wood or wood-fuel derivatives that do not give off excessive smoke, gasses, or particles into the atmosphere.
Different species of wood contain different levels of volatile organic compounds that give off more smoke, and some produce more creosote that cause the wood to burn less effectively and clog up the stove and pipes. Wood that has not been seasoned properly contain a lot of moisture that will give off smoke and burn less efficiently.
Safety of children and family
Firehouse sells very effective fire screens and fire gates that look attractive and keeps everyone safe from direct contact with the stove.
Which is the best Wood-Burning Stove?
There are too many factors involved in choosing the correct stove for your needs and tastes to give a definitive list. Those lists that are printed, will be misleading because they usually merely list some of the top manufacturers, favoured by the author and do not take individual circumstances, requirements and tastes into account.
Just some factors to consider before you buy the stove best suited to your needs, tastes and décor are:
- The correct size of stove for the room or area you want to heat.
- The warranty offered.
- The heat output and efficiency rating of the stove.
- The design style that will best match your décor.
- Whether you require a free-standing stove, built-in stove or insert-stove that could be installed in an existing fireplace.
- Whether you require a wood-burning stove designed for indoor or outdoor purposes.
Installation of wood-burning stoves
Installing a wood-burning stove is best left to the professionals to ensure there are no safety issues. The manufacturers of wood-burning stoves usually offer a longer warranty on stoves installed by registered professional installers.
A wood-burning stove that is installed incorrectly can be a fire hazard and can cause carbon monoxide or smoke to build up in the home.
How much clearance is required for a wood-burning stove?
- The wood-burning stove should be placed on a non-combustible hearth to protect the floor and area around it for at least 300 mm (12 inches).
- The clearance between the top of the stove and the ceiling (or anything above the stove) should be at least 915 mm (36 inches)
- When installing a wood stove in front of a window, the clearance is at least 915 mm (36 inches) from the glass.
- Minimum distance from any combustible material: 915mm (36 inches).
- Minimum distance from a non-combustible wall: 300 mm (12 inches) A non-combustible wall is required to a minimum height of 1200 mm (48 inches) above
- the hearth.
- By building a professionally designed outer casing around the wood-burning stove, these clearances could be reduced, but this should only be done by professional installers, taking into account the Building Regulations and Health and Safety Act.
How much does a top-quality wood-burning stove cost?
Visit the Firehouse website for the price and installation costs of the whole range of the best quality wood-burning stoves.
Typically, prices will vary from about £800 to more than £2000. Both cheaper and more expensive models are available, according to size, design, output, etc. At the very top-end, premier stoves will cost more than £8000.
Installation costs will be determined by factors such as the complexity of the job, the flue system selected, accessibility, etc. Obtain a free online quote from Firehouse, or you can visit our Kendal showroom.
Ask the Experts
Firehouse has a dedicated team of technical staff who are all HETAS approved and registered who can give you expert technical advice on the stove, its placement and installation.
Firehouse stocks all the leading brands and can give you unbiased advice on the stove that will best suit you and your circumstances.
Firehouse has a professional team of designers who can assist you with the best advice on design, décor and layout.
Our professional installers will ensure that you get the best out of your stove and that it will last for a very long time.