FAQ

Building Regulations for chimney installation

Any work that affects an existing chimney (including installation of a stove or flue liner) or creates a new chimney is considered building work and sofalls withing the remit of the building regulations department of the local authority.

The government issue an approved document, which contains practical guidance on ways of complying with the requirements of the building regulations, which deal with combustion appliances. In the UK, Document J of the building regulations applies to flues and chimneys. These must be adhered to for safety and legality.

Building Regulations

Fitting a flue liner/chimney system yourself

You must notify building control before installing any chimney (unless you are approved to self-certify, as are HETAS engineers)

You do not have to use a professional installer. If installing the stove into an existing fireplace/chimney and not using a new chimney liner then the installation is very straightforward for a person with average DIY skills. Installing a flexible chimney liner or complete twinwall system is a larger job and may involve ladders or scaffolding if external access to your roof is needed, but is still technically straightforward, so no specialist knowledge or skills are required.

If you complete the work yourself then the local council building control should be informed and they can then inspect the work on completion to sign it off. Alternatively, if the work is done by an installer who is accredited by one of the relevant Competent Person Schemes such as HETAS then they can sign off their work and provide you with a certificate.

Planning permission

This is not normally required. Installation of a stove and/or new flue system would not usually have anything to do with the local planning authority. If your property is a listed building then permission may or may not be required. If you intend your new flue pipework to run up the outside of an external wall then depending on the position (e.g. side or front of house) you may need to check with the local authority planning department.

Do I need to line my existing chimney?

Most houses built after 1964 should have a concrete/clay inner liner in which case you probably don't need to reline unless there is a problem with your existing system.

Older houses will normally just be exposed brick inside - it is not a legal requirement to line these older chimneys unless they are leaking, but there are often advantages to lining such as increased draw, peace of mind of having a sealed system top to bottom, and reduced risk of a chimney fire or leakage etc.

The existing chimney/flue should be swept clean before any stove installation and checked for condition and correct operation. A smoke pellet should be burned at the bottom to check for any leaks or blockages. Your local chimney sweep should be able to advise on your chimney condition if you are not sure.

We always advise that chimneys in older properties should be lined.

You must notify building control before installing any chimney (unless you are approved to self-certify, such as HETAS engineers).

Chimney design rules

• The minimum chimney height recommended for the minimum performance of wood-burning and multi-fuel appliances is 4.5m from the top of the appliance to the top of the chimney.
• The distance between the cowl of the flue and the adjacent roof/wall/structure should be higher than 2.3 meters.
• A maximum of four bends (up to 45º angle) is allowed. In the case of four bends; a sweeping door in between the two outer bends is required.
• In case of an offset; a maximum of 20% of the flue length can be non vertical (best practice).

Flue sizes

Most solid fuel appliances in the UK have either a 5" (130mm) or 6" (150mm) flue outlet on the top or rear of the appliance. You will normally then use the corresponding sized vitreous enamel flue pipe for the first section of flue from the stove to take you into the chimney. From that point, you will then usually have to change to a minimum 6" (150mm) flexible chimney liner or rigid insulated flue system. If you order a flexible liner kit or full twinwall flue system from us, it will come with the suitable adaptor to connect to the 5" or 6" enamel pipe. That applies to most solid fuel appliances. The exception is for DEFRA Approved stoves, which have a 5" (130mm) flue outlet. They can legally be used with a 5" (130mm) chimney liner or full flue system as they produce fewer smoke particles than other stoves.

Note: All installations are to be carried out according to UK Building Regulations, Document J. The tips on this page are meant to help you to do so, but in no way should be considered as a replacement of the instructions and rules of document J.

Click here for more info on flue regulations.

Single wall flue pipes

Single wall, uninsulated flue pipe must be at least three times its internal diameter from combustible materials.

This means that your 5″ flue pipe should be 15″ away from combustibles, and your 6″ flue pipe should be 18″ away from combustibles, in any direction. You must also be sure you make the connection/change from single wall stove pipe to twin wall flue pipe at least 150mm before passing through a non-combustible wall or ceilling.

The combustible material can be heat shielded. The flue must be at least 1.5 times its external diameter away from the heat shield and, the heat shield must extend at least 1.5 times the flue's external diameter to each side of the flue. There then has to be an air gap of at least 12mm between the shielding material and the combustible material.

Twin wall flue pipes

The twin wall flue, because it is insulated, only has to be a minimum "x"cm from combustibles. “x” is usually 5cm, 6cm or 7cm, depending on supplier. Please note that our twin wall flues should be 60mm from combustibles.

To the Stove pipes To the twin wall flue pipes

Yes you are allowed to do that, but you must abide to document J of the building regulations. Also a building control officer has to inspect and sign off the work.

It is better to contact building control before you start the installation, to make sure you are compliant.

Chimney Heights and Termination

Simple rules

Within 600mm from the ridge
The flue has to end minimum 600mm above the ridge.

More than 600mm from the ridge
The distance between the cowl of the flue and the adjacent roof/wall/structure should be more than 2.3 mtr.

For the height of the flue on the roof this means:

All the rules

The minimum chimney height recommended for minimum performance of wood burning and multi fuel appliances is 4.5 m from the top of the appliance to the top of the chimney. In practice 3.5m is often enough.

The distance between the cowl of the flue and the adjacent roof/wall/structure should be higher than 2.3 mtr.

Within 600mm from the ridge: Flue has to end minimum 600mm above the ridge.

The diagram below, taken from Document J (building regulations), shows the minimum flue discharge heights and positions for all wood burning and multi fuel applications.

In some cases, particularly when chimneys are towards the bottom of a sloping roof or at the eaves, it may be necessary to increase the chimney height above these minimum mandatory requirements. The reason for this is to clear pressure zones created by wind hitting the roof and nearby structures, like trees, which may interfere with the up draught required by the appliance or fire.

The maximum freestanding stack height above the roof for a traditional masonry chimney is 4.5 times the narrowest horizontal part of the chimney.
In the case of stainless steel system chimneys, the manufacturer’s installation instructions should be consulted; however in most cases it will be around 3 metres. This measurement is taken from the last point where the chimney stack passes the through or past the edge of the roof up to the chimney capping or termination. Tall chimneys may need bracing, always consult the manufacturer for advice.

For buildings with flammable roofs such as felted, thatched, or shingle roofs the flue or chimney the regulations are different. The flue or chimney must terminate at a minimum1800mm above the combustible surface.

A flue is simply a passage for exhaust gases from the oven or stove to the outdoors. A flue may be a duct, pipe, vent, or chimney.

So a chimney is a flue. A flue is not necessarily a chimney. Read our full article here.

Read our article about the different types of chimney flue.  

To the chimney flues

Gas stoves for conventional flues

If you have a gas stove for conventional flues, then you will need a functioning chimney, which is fitted with a flue. This is because this type of gas stove expels exhaust gases using a flue.

In case you don’t have a chimney, you will need to fit a twin wall system.

Your gas stove should specify what size diameter flue is required for you to install it. This is usually 5 inches, though you should always check before you buy one.

Balanced flue gas stoves

Balanced flue gas stoves are very popular in homes without chimneys. They are designed for use with gas only, not solid fuel.

A balanced flue gas stove requires you to have two pipes fitted to the outside of your home. One pipe draws in the fresh air, whilst the other expels waste fumes. Balanced flue gas stoves are highly efficient.

Some balanced flue gas stoves come with the required flue parts, while others require you to buy them separately.

In most cases, installing a balanced flue is easy. They can be fitted horizontally through almost any external wall. If you only have internal wall space to put your stove against, you might still be able to fit one – it will just take some extra work.

Chimneys are typically constructed of bricks, mortar, or another masonry.

The term flue refers to the passage by which smoke, gas, or products of combustion are moved to the outdoors. Ducts, pipes, vents, and even chimneys can all be considered types of flues.

So a chimney flue is a duct or pipe; either in a chimney or as stand alone flue.

To the Chimney flues

Open flue – An open flue stove draws combustion air from the room where it is placed. The exhaust gases rise in a vortex up the open flue.

Closed flue – An air duct brings combustion air directly to the stove.

Class 1 chimney (traditional chimney)

These are the brick chimneys you get - mainly on older properties, that were used to facilitate an open fire. They rely on the natural circulation of hot air to remove waste gases from the fireplace.

Which types of fire can you have with a traditional chimney?

The internal diameter of the chimney will be 7 inches or more and so can cope with most heating systems: Class 1 or 2 solid fuel fires, electric fires, gas fires, and gel fires are all suitable. However if the outlet of the heater is smaller than 7 inches, problems of condensing smoke may arise.

Note: Over time, older chimneys may not be sealed and therefore will require a flue liner.

Class 2 chimney (pre-fabricated chimney)

A prefabricated flue will either be used on older properties where a chimney has been lined with a steel flue, or on a newer property with a steel flue built in. They are made up of interlocking metal flue pipes. You can easily identify a prefabricated flue by the metal cowl on the roof, which looks like a thin metal chimney.

There can be no more than four bends in the chimney, and bends can be of a maximum of 45 degrees.

In the case of four bends, there must be a soot door between the second and third bends (as per building regulations).

For more information on bends see our full article here.

Appliances

The ideal flue size is typically determined by the exhaust outlet of the stove or appliance. You never want it to be smaller than the appliance exhaust hole.

The building regulations (Document J, page 30) require that the minimum flue size for stoves is as follows:

- Up to 20kW burning smokeless fuel - minimum 125mm diameter.
- Up to 30kW burning any fuel - minimum 150mm diameter.

So the regulations recommend a minimum flue size of 150mm for any stove (on which wood could be burnt) unless it is DEFRA Exempt.

Open fires including flame effect open gas fires.
Minimum 200mm diameter for fire openings up to 500mm x 500mm.
Larger fires require a flue area equal to 14-16% of the total area of the fireplace opening. (Minimum flue diameter 180mm for gas effect fires).

To the Chimney flues

Whenever you have a wood-burning stove installed in a fireplace, you will have a register plate above the stove blocking off the bottom of the chimney.

A closure plate is used when a chimney has no stainless steel liner. It closes off the chimney at its base, just above a wood-burning stove.

A register plate is used at the bottom of your chimney to close off the opening to the chimney, and must be sealed so it is gas-tight. A register plate will come with a pre-cut hole or access hatch.

It MUST be made of stainless steel (or other non-rusting metal like galvanized steel)

Building Regulations for Chimney Liner Installations

Any work that affects an existing chimney (including installation of a stove or flue liner) or creates a new chimney is considered building work and so falls within the remit of building regulations.

The government issue an approved document, which contains practical guidance on ways of complying with the requirements of the building regulations, which deals with combustion appliances. In the UK, Document J of building regulations apply to flues and chimneys. These must be adhered to for safety and legality.

Building regulations

A chimney liner may be necessary for an older property if the flue inside your chimney is no longer safe to use. A CCTV inspection carried out by a chimney professional will clearly show the condition of your flue.

To the Chimney liners

Wood stove
It is usually recommended you line your chimney to keep it working as safely and efficiently as possible. Flue liners are needed for several reasons:

• Installing a stainless steel chimney liner is an easy way to repair an unsafe, inefficient, or damaged chimney.
• Large flues over 200mm might need a smaller flue liner to keep the stove working without losing heat.
• If the chimney is too cold, smoke won’t rise through the chimney properly. This can leave tar and condensation, which eventually bleeds through the wall into the house, leaving stains.
  It is very important to burn dry wood and have a chimney liner swept every 6 to 12 months depending on use.
• Chimney fires are a hazard in unlined flues, but with a flue liner they are very rare and contained within the tube.

Although it is not necessarily a legal requirement to fit a flue liner for a woodburning stove, most stove installers would recommend you install one as in most cases it can be hard to determine the quality and potential performance of the chimney just by looking at it.

We recommend 316-grade chimney liners for stoves that will be used for burning seasoned wood and the occasional use of smokeless coal.

We recommend a 904-grade chimney liner for stoves burning a mix of seasoned wood and smokeless coal or smokeless coal on its own.

Gas fire
If you have an existing flue or chimney, you should look for a conventional flue gas fire. These fires use the natural circulation of heated air to draw the products of combustion out of the property. Existing conventional flues come in two main categories: Class 1 and Class 2.

- Class 1 flue: a traditional brick chimney, which was once used for an open fire. It usually has a minimum diameter of 7” (178mm). It is also possible to build a Class 1 flue into a new build property, usually using a pre-fabricated steel or masonry flue system. if your chimney has deteriorated, it must be lined with a stainless steel flexible liner to make the flue safe. Nearly all conventional flue gas fires can be fitted to a Class 1 flue.

- Class 2 flue: a metal pre-fabricated flue with a 5” (125mm) diameter, terminating in a metal gas cowl on the roof. A wide range of gas fire models has been specially designed to be suitable for Class 2 flues.

To the Chimney flues

The type of fireplace will determine the size of the flue liner for example an open fire fireplace will require a flue liner that ranges in diameter from eight to ten inches.

The ideal flue size is typically determined by the exhaust outlet of the stove or appliance. You never want it to be smaller than the appliance exhaust hole.

The building regulations (Document J, page 30) require that the minimum flue size for stoves is as follows:

- Up to 20kW burning smokeless fuel - minimum 125mm diameter.
- Up to 30kW burning any fuel - minimum 150mm diameter.

So the regulations recommend a minimum flue size of 150mm for any stove (on which wood could be burnt) unless it is DEFRA exempt.

Open fires including flame effect open gas fires.
Minimum 200mm diameter for fire openings up to 500mm x 500mm.
Larger fires require a flue area equal to 14-16% of the total area of the fireplace opening. (Minimum flue diameter 180mm for gas effect fires).

A chimney liner is obligatory if you are installing a woodburning stove, gas fire or open fire in a new build property to comply with Document J of current building regulations.

Older chimneys will often require a modern lining solution for the following reasons:

• The flue may have lost integrity and can leak smoke into rooms .
• Condensation or tar can seep through chimney walls causing staining.
• Bad draw: Lining with insulation included can improve the operation of the appliance and flue – particularly important when the chimney is situated on an external wall.
• Poor up-draught: Defective flue systems may be eroded and rough. This will cause frictional resistance to the flow of the gases resulting in poor up-draught.
• Large flue: Some appliance manufacturers specify smaller flues for efficient operation.

A CCTV inspection carried out by a chimney professional will clearly show the condition of your flue.

To the chimney liners

Insulated flues improve the draw.

Do we need to insulate when we fit a chimney liner?

• If the chimney is exposed (on an outside wall), or
• the stack is particularly tall, or
• If the flue is of a large diameter

Then the answer is a definite YES! Insulated liners keep the flue gases warmer, increase the upward speed of those gases and help prevent condensation.

Otherwise it is not necessary. The air between the liner and the flue will insulate the liner.

However, it is not difficult to insulate a liner (just adds cost) so it is up to you.

Chimney wrap

Installing with a chimney wrap: Instead of feeding the flue down the chimney, you haul it up the chimney. The person at the top has to have a very secure platform (e.g. scaffolding). A cherry picker might work but add the liner and wrap weight to the maximum allowed by the cherry picker.

Vermiculite

Vermiculite (Micafil) is supplied in bags. It is very light and will be taken by the wind easily.

Vermiculite cannot catch fire and is used to insulate chimney liners.

It is poured into the top of the chimney and will cascade down the chimney onto the closure plate, filling the gap between the liner and the chimney itself all the way to the top.

Vermiculite is only suitable for chimneys with a few inches of an air gap.

Click here for more information

Yes, you can!

Installing a stainless steel chimney liner is an easy and economical way to repair a deteriorated chimney. You will be able to install a chimney liner after reading the instructions and you can do the job with common household tools.

Installation instructions

Many factors will affect the price of installing or replacing a chimney liner:

- whether it is a DIY job or not
- the size of your chimney.

Materials will cost around £200 ; the chimney flue will be £25 - 40 per meter.

On average, a chimney liner installer will charge between £150 to £250 a day for a flexible flue liner, depending on their experience and knowledge. The job normally takes half to one day.

To the chimney liners

You can install your flexible liner from either the top or bottom of the brick chimney stack. However working from the top is lighter, gravity will help you to move the liner through the chimney.

Whichever way you choose to install the liner, please ensure that you have sufficient clearance around the outside of the liner to ensure the least amount of friction, or the possibility of catching any bricks within the chimney stack, does not occur.

Installation instructions

No, it is not!

Installing a stainless steel chimney liner is an easy and economical way to repair a deteriorated chimney. You will be able to install a chimney liner after reading the instructions and you can do the job with common household tools.

Installation instructions

A flexible liner can generally be fitted within one day (4 - 8 hours on average)

Installation instructions

A chimney liner or flue liner only needs to be replaced if it is no longer working properly.

If you have had a chimney fire in your stainless steel liner it will need to be replaced before the chimney can be safely used again. This is because the extreme temperatures endured during a chimney fire change the structure of the stainless steel and it will no longer be fit for purpose.

Sometimes the existing flue is simply far too large for modern appliances, but the main reason is that many old chimneys will fail the smoke test, which means that the flue is leaking smoke and fumes into the building.

If you have a modern, efficient wood-burning stove, you will require a Class 1 flue liner that is normally made of stainless steel. Flexible 316-grade stainless steel liners are the most popular lining for an existing chimney as they are the most cost-effective and the work can usually be carried out in one day or less with little upheaval or mess.

A stainless-steel liner installed correctly will last many years, and they are often guaranteed for 10 years or more.

Gas stoves only require Class 2 flue liners, which are much cheaper, and lighter, yet still, meet safety regulations.

Type of steel

Flexible liners are formed using two layers of stainless steel, the grade being either 316 or 904.

The 316 liner is suitable for most domestic wood burning stoves.
The 904 is a higher-grade liner. It is more resistant to corrosive chemicals than 316 grade and is suitable for multifuel appliances, the use of smokeless fuels and boiler stoves.

Diameter

Your appliance installation instructions should specify the flue liner diameter - If this is not clear - we recommend that you contact the manufacturer.

Building regulations approved Document J also contains guidance on flue liner sizing.

In any case, you should never reduce the diameter of the flue at any point in your installation. E.g. if your woodburning stove has a 6inch 150mm diameter outlet your flue should not be smaller in diameter.

To the chimney liners

Class 1 flue liners:

A Class 1 flue liner (or solid fuel flexible liner) is a twin skin flexible flue liner suitable for appliances burning wood, solid fuel and heavy oil.

Our Class 1 flue liners are made from either 316L grade stainless steel or 904L grade stainless steel (carrying a 10yr and 25yr conditional warranty respectively).

Class 2 flue liners:

A Class 2 flue liner is a single wall flexible flue liner and is suitable for appliances burning gas or 28 Second Oil (Kerosene), where the temperature does not exceed 260°C.

A single wall flue pipe is also called vitreous enamel, single skin flue or connecting flue pipe or even starter pipe. The term ‘single wall’ refers to the fact that there is only one layer of steel with no insulation.

A twin wall flue is also known as a double-skin flue. A twin wall flue pipe is manufactured from stainless steel and is made up of two steel walls, kept separate by a layer of high-grade insulation.

Twin wall is usually provided in a stainless steel finish, which can also be powder coated.

The layer of insulation in twin wall flue keeps the flue gases warmer and allows the flue to perform correctly and efficiently, whilst also reducing the build-up of condensates within the flue system. At the same time the outside temperature of a twin wall pipe is much lower than for a single wall flue.

The centre of the inner tube is where the smoke from your stove will travel upwards through. This is then encased by a layer of insulation, which is then wrapped up in the second outer wall.

When can I use it?

• Twin wall flue systems are used with a stove when it is fitted into a property where there is no masonry chimney. It can run internally or externally and it achieves higher temperatures due to the layer of insulation.
• You cannot use a single wall flue pipe in place of a twin wall flue pipe. A single wall flue pipe is not insulated and therefore loses a lot of heat. The layer of insulation in twin wall flue keeps the flue gases warmer, allowing the flue to perform correctly and efficiently, whilst also reducing the build-up of condensation within the flue system.

To the twin wall flue pipes

Yes, it does!

The outside of a twin wall flue can get up to 85 degrees C, close to the stove. Higher up the temperature will drop gradually.

A single wall pipe, which is not isolated, can get a temperature up to 600 degree C close to the stove.

A twin wall flue is a chimney pipe that has a layer of insulation between two walls; this reduces the heat transfer to the outer wall of the pipe, making it safer for humans and less of a fire risk. The high temperature of the smoke ensure a good draw.

It is supplied in sections that are connected.

To the twin wall flue pipes

Twin wall flue systems are used with a stove when it is fitted into a property where there is no masonry chimney. It can run internally or externally and it achieves higher temperatures due to the layer of insulation.

You cannot use a single wall flue pipe in place of a twin wall flue pipe. A single wall flue pipe is not insulated and therefore loses a lot of heat. The layer of insulation in twin wall flue keeps the flue gases warmer, allowing the flue to perform correctly and efficiently, whilst also reducing the build-up of condensation within the flue system. 

At the same time, the outside temperature of a twin wall pipe is much lower than for a single wall flue. If you want to know more, see our ultimate guide to the twin wall flue.

To the twin wall flue pipes

Protection around a twin wall flue

The idea of putting a loft cage around a twin wall flue, is that it keeps flammable items safely away from the chimney in places where they might get too close to the flue . Twin wall flue doesn't normally get very hot on the outside, so you might not think this is too much of a problem... But, if you have a chimney fire then the outside can get very hot when the internal temperature rises up to 1200ºC. Th is is the situation that you are preparing for.

When do you put a loft cage around a twin wall flue?

Where twin wall flue passes through a cupboard or roof space, then a guard should be placed around it.

When do you have to box in twin wall flue pipe?

A bedroom or a storage space is a great example where toys or curtains may easily get too close from the flue/chimney. In this situation, guarding is more commonly done by boxing the flue in, although some type of mesh is still a way to do it. We recommend solid boxing in because, it means that nothing can accidentally fall into the void and you also need consider the fact that, there is ventilation where the twin wall passes through the floor. A mesh guard would let the noise, smells and more crucially smoke pass from the room below to the one above. It's worth bearing this in mind and to make sure your boxing well made and sealed when you build it.

The building regulations (read Document J, page 24-25)

“Where a chimney passes through a cupboard, storage space or roof space, providing a guard placed no closer to the outer wall of the chimney than the distance in (a) above”.

Under “location and shielding of flues” it also reads:

“Fluepipes and factory made chimneys should also be guarded if they could be at risk of damage or i f they present a hazard to people that is not immediately apparent such as when they traverse intermediate floors out of sight of the appliance”.

A stove pipe enables you to connect a wood burner or multi-fuel stove to your chimney or flue installation.

Our stove pipe is a matt black, single wall stove pipe. Its enamelled interior and exterior ensure the durability of the colour and increases its resistance to high temperatures and condensation. At 1mm steel thickness, it can be easily cut to the required size using fine-grain grinding disks.

To the Stove pipes

Connecting a flue liner to a stove

Installation of a stove pipe

Single wall elements should only be used as a connecting piece between your stove and the chimney stack.

Stove pipes should never pass through walls, ceilings, floors or windows. Other products should be used for this purpose, such as the twin wall flues.

Avoid bends in your chimney if possible; the fewer bends, the better the upwards draught will be. UK building regulations and HETAS recommend no more than four 45-degree bends in any one system.

When installing a wood stove flue, remember that the higher the chimney, the better the draugh will be.

The ideal flue assembly rises straight up from the appliance flue collar and directly into the chimney with no elbows. The system can include inspection panels to allow easy access.

A straight flue assembly offers the least restriction to gas flow and results in a stronger draugh. Straight assemblies also need less maintenance because there are no corners for creosote deposits to accumulate.

A perfectly straight stove pipe assembly is another good reason to install chimneys up through the warm space of the house, instead of out, up and outside the wall.

The (inner) diameter of your stove pipe is usually the same size as the flue collar on your stove. Follow manufacturer recommendations whenever applicable. Never use a chimney that is smaller in diameter than the flue size of the appliance it is being connected to. An improperly sized chimney results in excessive creosote formation and poor draugh.

Be sure to install a chimney cowl to prevent animals and rain from entering the chimney and to improve an upwards draugh.

Bad draw

A bad draw is often caused by a contaminated connector or flue. Check all existing valves in the connecting pipe are in the correct (open) position.

When smoke comes back into the room this can be because the flue is not yet warmed up. The chimney only has a good draw if the smoke is warmer than the outside air. Heat up the flue by rolling up a piece of newspaper into a torch and keep it in the flue until the smoke is going in the right direction. Chimneys that run along the outside of the house, particularly, require some pre-heating.

Factors influencing the draw

The build of the flue

- The diameter of the chimney must not be smaller than the diameter of the outlet of the stove.
- A higher chimney means a better draugh. If the draugh is not sufficient sometimes, a higher chimney is sufficient to improve the draw.
- A chimney with a round insert pipe normally gives a better draugh than a square.
- The use of elbows in the pipe reduces the pull. If there are bends to be used, 2 x 45 ° is preferred over 1 x 90 °.

The supply of combustion air is of essential importance for the tensile

An open fireplace needs about 300 m³ of air per hour, and a "closed" fireplace approximately 30 m³ per hour.
A kitchen fan or hood sucks much more air than a chimney. This can lead to a kickback. In other words, the kitchen hood draws air into the room coming from the chimney, thereby drawing smoke into the room.

Opening a window should solve this problem immediately.

Influence of the wind

The draw can be disrupted by:
- high trees
- cliffs
- high buildings

This problem can usually be solved by making the chimney higher. In extreme cases, an exhaust fan can be installed. A draugh regulator can stabilize the draugh of the chimney.

Reduction of draw

At high temperatures, the fireplace provides a strong pull. The best results are achieved when the height and diameter of the chimney are aligned with the device in use. If the pull is too strong, the heat can quickly be sucked into the chimney. Too strong a draft can be adjusted with valves, draugh regulators (insert pipe or chimney) or restrictors. The use of multiple bends in the flue pipe reduces the pull.

For more information click here

A common problem with wood-burning stoves with large doorways.
When the door of a burning stove is opened, the chimney needs a strong draw to maintain a negative pressure in the stove. This will only work if the chimney has a large enough cross-section and a sufficient height. If not, a stove with a smaller door would have been a better choice.

The following tips can sometimes help:

• Check whether any shut-off valve in the connecting pipe is not in the correct position.
• Open the door a little first and wait 10 -20 seconds before slowly opening the door further as far as necessary.
• Check whether the connecting pipe between the stove and the chimney is clean.

There are other possible causes:

The external outlet of the chimney or flue no longer has a free passage of air. This could be because it is blocked by trees or other tall plants, or a bird or an other animal has nested in your flue. Solution: remove the obstructing branches, leaves, or nests.

The problem can also be that the chimney is simply not high enough, for example because an extension to the house or a new garage is higher than the flue pipe. Solution: increase the height of the chimney or flue.

Winds, especially down draugh (between tall buildings), can blow smoke back up the chimney. Solution: Check the hood on the chimney (if there is one), and replace or add it if necessary. However, make sure that this does not reduce the effective opening of your chimney.

Turn off all fans near the stove: Your wood stove’s blower fan, kitchen fans, and even bathroom fans can create partial vacuums that suck smoke out of your stove’s open door. By turning off these devices, it is easier for smoke to stay where it belongs – inside your stove.