Despite the wide range of modern and modern heating systems, solid fuel stoves are not going to give up their positions of popularity at all. This is understandable - the presence of such a heating facility gives a certain sense of autonomy - even under the most adverse circumstances caused by interruptions in the supply of other energy sources, a stove with a supply of fuel will help both heat the house and cook food for the family.

But the stove will only work efficiently and safely if it is designed, built or built to the right specifications. And one of the key conditions for the functioning of the furnace is a well-thought-out and reliable system for removing combustion products -. There are several options for the equipment of this system - from laying out a classic brick pipe "the old fashioned way" to the use of completely new, sometimes even unexpected technological solutions using modern composite materials. And at the peak of popularity in this matter in our time, probably, are sandwich pipes for furnaces.

What are sandwich pipes for furnaces, how they differ, what you need to know about their choice and the basic rules for designing a system - all this in this publication.

What are sandwich pipes and their main advantages

The developers of sandwich chimneys set themselves the task of minimizing the disadvantages that are characteristic of almost all chimneys, regardless of the material they are made of.

Any chimney is subject to negative destructive influence both from the inside and from the outside. The combustion products have a high temperature and a very aggressive chemical composition, which leads to erosion or corrosion of the materials of the internal channel. In addition, over time, the chimney channel becomes overgrown with soot, which reduces the patency of the pipe, and as a result, the efficiency and safety of the furnace.

Outside, in open areas, external factors act on pipes - high humidity, precipitation, fluctuations in air temperature outside. In addition, the temperature difference between the outside and inside the chimney leads to the active formation of condensate - and this, in turn, increases the likelihood of soot deposits.

"Classic" brick chimneys, although considered time-tested, have a whole "bouquet" of shortcomings.

• Firstly, the rectangular section of the channel is by no means optimal - unnecessary turbulence of the gas flow inevitably occurs in it. Reduce overall traction.
• Secondly, it is impossible to achieve ideal smoothness of the channel walls - the porous structure of the brick will still contribute to soot deposits.
• Thirdly, the brick chimney itself is a very massive structure, quite difficult to build and requiring a reliable foundation.

How to lay out a brick chimney

If this option is chosen, then a number of important rules must be strictly observed. How to fold a brick chimney on your own - in a special publication of our portal.

• And fourthly, even a high-quality brick, under the influence of a whole complex of negative influences, is prone to erosion, and the picture of crumbling chimneys is by no means uncommon.

This means that in order for the chimney to be optimal, it must be made with a round cross section, smooth inner walls, from heat-resistant, erosion-resistant and corrosion-resistant material. and light enough not to weigh down the entire furnace structure. It would seem that modern types of stainless steels meet all these requirements. However, such a simplified scheme is impossible for a number of reasons:

• Any metal has a high thermal conductivity, and a high temperature difference inside the chimney channel and outside can have a destructive effect on thin walls, and most importantly, leads to abundant condensed water vapor, which is always contained in the combustion products.
• The rapid cooling of gases in open areas of the chimney will inevitably lead to a decrease in the draft of the furnace.
• The sections of the metal pipe located inside the building are heated to very high temperatures, and this is unsafe both from a fire point of view and from the standpoint of a high probability of accidental injury - a burn.

This complex of problems would be completely or to the maximum extent possible resolved by creating a sandwich chimney structure. The inner channel and the outer surface of this design are two separate metal cylinders separated by a layer of heat-resistant thermal insulating material with a markedly low thermal conductivity.

The inner duct must always be made of a special type of stainless steel, with a reliable welding of the seam - usually argon welding is used.

The outer casing is also metal, but options are already possible here. Of course, the most resistant to external influences will be a stainless steel casing. However, sometimes, in order to save money, they also purchase cheaper options in which the outer pipe is made of galvanized steel.

Mineral wool made of basalt fiber is most often used as a thermal insulation layer, as it is the most resistant to high temperatures. The high density of basalt wool (from 120 to 200 kg/m³) provides the necessary structural strength. The thickness of this layer can vary - from 25 and even up to 100 mm. It depends on the parameters of the heating equipment and, to a certain extent, on the climatic conditions of the region.

The great convenience of such a design is that it carefully considers the issues of mounting individual parts into a single system. For this, connecting nodes are provided in the form of sockets and narrowed sections, special clamps, stoppers, sometimes flanges, etc.

Such a chimney system for the furnace immediately acquires a number of important virtues :

• The mass of the entire chimney system assembly is not so large, that is, it will not be necessary to strengthen the foundation of the furnace and its structure, as is the case with a brick pipe.
• The chimney can be placed on brackets vertically along the outer wall of the building. And this is a simplification of assembly, especially when passing through floors, and a significant saving of usable space inside the premises.
• The system is very "flexible" in terms of the possibilities of its placement. Manufacturers provide a wide range of additional components and components that allow you to quickly and reliably assemble the chimney of the required configuration. It becomes possible to bypass possible obstacles without resorting to large-scale alterations in the design of the house.

• The temperature difference between outside and inside is compensated by a thermal insulation layer. This stability guarantees normal stable traction, and condensation and soot deposits are minimized.
• The outer surface of the sandwich pipe, when properly assembled, does not heat up to critical temperatures, that is, the safety of the chimney operation is significantly increased.
• The assembly of such a chimney, subject to all technological recommendations, is an accessible and intuitive event that does not require any special training.

Such chimneys also have certain limitations :

• A quality set will be quite expensive.
• Over time, under the influence of high and low temperatures, signs of depressurization may appear at the junctions of individual nodes - this requires special attention: regular checks and, if necessary, preventive maintenance.
• Limited overall service life. Despite the fact that high-quality stainless steel is highly resistant, aging processes also do not bypass it. As a rule, manufacturers guarantee up to 15 years of trouble-free operation of their products. However, any other chimney for such a period will most likely require some kind of repair and restoration work.

How to choose a metal sandwich chimney

As already mentioned, the cost of such a chimney system is quite high, and replacing low-quality pipe sections can result in considerable costs. Therefore, it is very important to be able to correctly evaluate products when choosing, so that disappointment does not come after one or two years of operation.

Selection criteria can be roughly divided into several categories. So, first of all, the quality of the materials used in the production of sandwich pipes is evaluated. The necessary linear parameters are selected - that is, the diameter of the chimney, the height of the future pipe, the thickness of the insulation layer. It is important to immediately think over the features of the structure being created in order to assess whether all the components are commercially available for its installation.

Assessment of the quality of manufacturing materials

To the untrained eye, all stainless steels look the same. The new pipe shines - but this is not at all a criterion for the quality of the metal.

The same "beautiful and shiny" pipe after a short period of time can be deformed and even simply burn through - alas, there is a lot of evidence of this on the Internet. And such a situation is a direct road to a fire or carbon monoxide poisoning.

Unfortunately, we have to state that the increased demand for such chimneys has also given rise to the "shadow sector" of their production, where materials are used that are of little use for such purposes. There is another situation when a perfectly high-quality sandwich was used in conditions for which it was simply not designed. For example, a pipe that is quite suitable for a gas boiler is unsuitable for use with a solid fuel stove.

Stainless steel grade

When choosing sandwich pipes, it is necessary to focus on the steel grade, which is used primarily for the internal channel. This parameter should be indicated in the passport documentation of the product, unless, of course, it is produced by a bona fide manufacturer. If the steel grade is not indicated, then it is better to look for another option.

So, the following grades of stainless steel can be found:

— AISI 430. Such steel belongs to the category of the most inexpensive. It is quite suitable for the outer lining of a sandwich, since its resistance to atmospheric phenomena is quite enough. But for the inner pipe, it is not suitable categorically. Its composition predetermines unimportant weldability, that is, it is very problematic to obtain a sealed seam. Such steel does not meet the requirements of increased heat resistance.

— AISI 439. This alloy is enriched with titanium additives, which significantly increases its resistance to corrosion and mechanical strength. Pipes made of such steel are quite suitable for any gas installations, as well as for solid fuel boilers and furnaces, but only for a small thermal power.

— AISI 316. This steel has a pronounced corrosion resistance to almost all aggressive substances. Thermal stability is average, so the pipe is only suitable for gas-powered equipment.

— AISI 304. Steel does not have the highest heat resistance, therefore it is usually not used by serious manufacturers from being used as an internal channel. Perfect for outer shells.

— AISI 321 and AISI 316i. They have excellent heat resistance and good ductility, easily amenable to high-quality welding. Such pipes are quite suitable for most types of boiler and furnace equipment, as they can withstand heating up to 850 ° C without deformation.

— AISI 310S. Fully versatile steel that can withstand temperatures up to 1000°C. It is quite suitable even for powerful solid fuel furnaces and boilers operating on the principle of afterburning pyrolysis gases. The only conditional drawback is the high price.

Knowing the parameters of your furnace, you can choose the optimal grade of stainless steel.

Do not forget about another way to check stainless steel. Of course, it will not give an accurate picture, but it will help you immediately avoid buying a low-quality fake:

It is necessary to take an ordinary magnet and try to “glue” it to the inner wall of a vertically standing sandwich pipe. The magnet should not be held - ideally it will just slide down. If it stays in place or goes down with visible braking, the “black” component of such steel is too high, and the pipe is unsuitable for a chimney.

Type of insulation material

As already noted, only basalt mineral wool should be used as an insulating material for the thermal insulation layer. In no case, no matter how attractive the price may seem, you should not purchase a sandwich pipe filled with glass wool. The thermal conductivity coefficient of glass wool is no worse, the heat resistance is completely different. At temperatures of about 300 ° C, its sintering begins, subsidence in size, and all its advantages are reduced to zero. In addition, fiberglass is very brittle, and the insulation layer does not differ in volumetric stability, it is prone to shrinkage.

In really high-quality sandwich pipes, manufacturers use heaters from leading brands - ROCKWOOL, PAROC and the like.

The diameter of the chimney channel and the thickness of the insulation

Manufacturers provide a fairly wide range of diameters. So, models are produced with an inner pipe from 110 to 300 mm, with different thicknesses of the insulation layer, that is, different external diameters of the structure.

The main parameters of a sandwich pipe are the diameter of the inner channel, the thickness of the insulation and, accordingly, the size of the outer casing

If new equipment, a boiler or a furnace is purchased, then the required diameter of the chimney pipe must be indicated in the passport data - this value should be followed. It is more difficult if the chimney is planned to be installed on a brick or home-made one - here it is important not to make a mistake with this parameter.

In this case, you can do it in several ways. The first, simple one, is to navigate according to the table showing the dependence of the thermal power of the equipment and the diameter of the chimney.

Thermal power of solid fuel furnace		Minimum section of a rectangular chimney	Pipe cross-sectional area	Minimum diameter of the inner pipe of a sandwich chimney
kW	kcal/hour
up to 3.5	up to 3000	140×140 mm	19600 mm²	158 mm
3.6 ÷ 5.2	3000 ÷ 4500	140×200 mm	28000 mm²	189 mm
5.3 ÷ 7.0	4500 ÷ 6000	140×270 mm	37800 mm²	220 mm

You can also focus on the approximate consumption of an existing furnace of one or another fuel. In this case, the following formula is used to calculate:

S=Vg/wg

S- cross-sectional area of ​​the chimney channel.

Vg is the volume of combustion products.

wg- the speed of movement of gases through the chimney (optimum is 2 m / s).

Thus, to calculate the diameter, it is necessary to apply the formula for the area of ​​a circle:

d = √4 ×S/π = √(4 ×Vg /wg) /π = √2 ×Vg /π

The value remains unclear. Vg. It is calculated as follows:

Vg = M × Vy × (1 +T / 273) / 3600

M- the total approximate mass of fuel burned in one hour.

Vy– specific volume of combustion products from combustion of 1 kg of fuel.

T- temperature at the outlet of the chimney

273 - the difference between the value of temperature zero in degrees Celsius and Kelvin.

3600 - the number of seconds in an hour, to bring the value to a single value.

So the formula looks like this:

d = √(2 × M ×Vу × (1 + T / 273) / (3600 × π))

Values Vy and T you can accept tabular ones using the table below.

Fuel type	Average calorific value of fuel, kcal/kg	Specific volume of combustion products from combustion 1 kg, m³/kg	Chimney outlet temperature, °С
Firewood, average humidity level 25%	3300	10	150
Peat lump or loose, air dried, humidity up to 30%	3000	10	130
Peat in briquettes	4000	11	130
Brown coal	4700	12	120
Coal	6500	17	110
Anthracite	7000	17	110

Surely, the formula will seem “heavyweight” to many, not conducive to independent calculations. To simplify the task, a calculator is placed below, in which the necessary arithmetic ratios are already laid down.

The efficiency of heating stoves and other similar devices largely depends on the design chimney in home.
Furnace chimney designed to remove volatile and gaseous products of combustion from the furnace and to create thrust to ensure the combustion process.
Until relatively recently, all chimney pipes were made either from brick, or from asbestos-cement pipes, or from black non-galvanized metal.
The thing is that at a temperature of the exhaust gases over 100 degrees C, zinc began to evaporate into the room, and its fumes are harmful to health. That is why they used non-galvanized metal, covering it from the outside with beautiful silver.
Today, chimneys are built from a variety of materials, and each of them has its own pros and cons. So let's try to figure out which pipe to choose for the chimney of your house so that it has served faithfully for decades.

Asbestos-cement chimney
Asbestos-cement pipes have been widely used since the middle of the last century. They were cheap, they were easy to manufacture, there was enough natural asbestos in the country. Moreover, such pipes could be used without any preliminary insulation for a variety of agricultural needs. That's just for the arrangement of chimneys, they were never intended.
At the time of land reclamation in rural areas, asbestos-cement pipes were not uncommon, and during the period of mass construction of private houses, they were already used as chimney pipes.
Many opponents of such an implementation immediately appeared - first of all, environmentalists who claimed that asbestos cement releases many bad compounds into the environment.
Although, according to scientists, the asphalt on the road is even more carcinogenic.
But, nevertheless, even the roofs of buildings today are covered with a variety of expensive roofing instead of cheap and durable asbestos.
All these fears and myths have little to do with asbestos-cement chimneys.
And at the same time, they are not at all safe - this material was never designed for high temperatures, and can burst already at 300 degrees C. Therefore, if you already put them, then just not at the stove itself - but as close as possible to the roof, where the smoke is already going a little chilled.
To prevent the danger of fragments flying and accidental fire (God forbid) in the hot part of the pipe, as well as in uncontrolled places (attic), it is better to wrap the asbestos-cement pipe with a sheet iron bandage.

There is also another point. Soot forms in any chimney, but the smoother its walls, the less soot lingers on them.
But asbestos-cement pipes just never differed in smoothness, and soot accumulates on them very, very much. And it’s easy for her to catch fire - any stove-maker knows this.
Moreover, if soot ignites inside an asbestos-cement pipe, it can break from temperature. This is dangerous.
Even asbestos-cement pipes are severely destroyed by condensate. Condensate is an aggressive environment from a mixture of combustion oxides and a very small amount of moisture.
Moreover, the oxides contain a good percentage of hydrochloric acid, which even destroys bricks, but asbestos also absorbs into itself, transferring all this to the structure in the form of unsightly spots with the same unpleasant odor.
So, if you decide to use an asbestos-cement pipe for the chimney, clean it as often as possible.
True, cleaning such pipes is difficult - it will not work to make revision windows in such pipes.

brick pipe

The construction of a brick chimney has a long history.
Such a pipe is laid out from red oven bricks simultaneously with the stove. A competent stove-maker knows exactly which brick to choose for the stove, even different inside and out, which brick is needed for the pipe inside the attic, and which one - from the outside of the chimney on the street.
The inside of the chimney should not be corroded by condensate, and the outside should not be washed away by rain and crack from temperature changes. Therefore, overheated, under-heated and raw bricks should be clearly distinguished.
A pipe made of this material needs periodic repairs. In addition, for do-it-yourself installation of a brick pipe, it is necessary to use a special solution that is resistant to the combustion process, but at the same time is plastic and heat-resistant.
Since the weight of a brick pipe is very significant, the entire stove-pipe structure is usually one piece and is placed on a separate foundation that is not connected with the house.
Brick chimneys and chimneys are also arranged inside the brickwork of the building wall.
Lay chimneys and chimneys with dressing, on lime or cement-lime mortar inside the house, and above the roof on cement mortar.
According to SNiP, wall channels are made of high quality solid red brick, with a seam no thicker than 10 mm. The inner surface of the channel is not plastered.
However, no matter how well such brickwork is done, the inner surface of the brick chimney is rough and it will still become covered with soot over time. In any uneven section of the chimney, soot accumulates more intensively.
The wall with the chimney channel inside is almost constantly wet from condensate.

Aggressive acidic condensate destroys the brickwork, the brick crumbles and sometimes even collapses into the channel and narrows its cross section.
To significantly increase the life of the chimney, it is necessary to periodically clean it at least once every six months.
The internal section of a brick chimney has a rectangular section, so when gases move in the corners, turbulences occur that reduce draft.
Therefore, an asbestos-cement or steel pipe is sometimes inserted into the internal channel.
The main disadvantages of a brick pipe are weight, size, complexity of repair and replacement.
But the aesthetics, fire safety and durability of brick chimneys exceed any of their shortcomings.

Ceramic chimney

Ceramic chimneys are also a modular system of elements of complete factory readiness.
In the simplest cases, they are a conventional ceramic pipe, but it is considered more appropriate to use sandwich structures that provide safe operating conditions.
Heat-resistant ceramics are acid-resistant and durable.
Some manufacturers claim a warranty period of up to 30 years, and an expected service life of up to 100 years.
The inner surface of ceramics is covered with a special heat-resistant glaze, which makes it absolutely smooth.
This does not allow the formation of turbulent eddies, the flow of gases passes through a calm laminar flow. Soot does not linger on a smooth ceramic surface.
The chimney of such pipes is the most durable. He is not afraid of either prolonged intense heating, or chemical aggressive environments, or corrosion. Its inner surface is very smooth, soot or ash almost does not linger in it, and as a result, pipe maintenance is minimal.
And ceramics is an excellent heat-absorbing material, and in combination with the expanded clay concrete box in which it is hidden, the outer surface of the chimney does not heat up at all. And this is a complete guarantee that your house will never fall into those sad statistics of houses that burn because of chimneys!
These elements have a significant total weight, so the ceramic chimney is installed on a separate foundation.
Brickwork requires considerable time, and the installation of a chimney with a ceramic pipe can be carried out in a short time.
Ceramic pipes are expensive and practical.

metal chimney
Metal chimneys are almost always made of stainless steel. They are a practically modular system of straight sections and fittings: adapters, bends, tees, umbrellas.
Such systems can either be embedded inside brick channels or mounted separately.
Stainless steel is heat-resistant and acid-resistant and condensate cannot corrode it.
Stainless steel is the most suitable material in terms of overheating, soot and getting wet. This material can even heat up to 500 degrees C - and it will not melt yet.
Soot does not accumulate on the smooth inner surface of the chimney.
Thus, due to the smooth surface without soot and a stable cross section, stable aerodynamic characteristics of the passage of exhaust gases are ensured.
Single-walled metal chimneys consist of one layer of stainless steel, and double-walled ones of two layers of metal and mineral (most often basalt) wool is laid between them.
These are sandwich systems. In this case, the outer surface heats up minimally, heat is retained perfectly throughout the entire chimney, and therefore there is almost no condensation on the inner surface.

Sandwich pipes are very technologically advanced and have been used quite often lately, especially for baths. The only thing is that when buying, you need to carefully check the quality of steel, because there are many cases of pipe burns and fires for this reason.
Sometimes, during repair or restoration work, a metal pipe is placed inside brick channels. This is called a "sleeve".
The low weight allows these chimneys to be installed without a special foundation.

There are also corrugated pipes. They are used exclusively to create turns and bends in the chimney, but almost never as the main pipe. But they are indispensable if there is just a beam above the furnace and it remains only to go around it. For more, they do not yet have sufficient anti-corrosion or thermal insulation qualities.
It should be noted that metal chimneys are not made of stainless steel. For example, for sauna stoves, some manufacturers offer thick-walled low-alloy steel pipes.
And craftsmen, when constructing bath stoves, quite often use cast-iron chimneys from sewer pipes.

Concrete pipes for the chimney

The main advantage of such pipes is the cheapness of the material, durability, maintainability and lack of seams. And you can make the pipes themselves at home by using a sliding formwork.
The composition of the mixture is as follows: three parts of sand, water and one part of Portland cement M400. Concrete is quite hard. It is better to make pipes monolithic, and there will be very little soot.
The only drawback of such pipes is their heaviness. This can be corrected by using expanded clay in the composition.

Vermiculite pipes
Vermiculite pipes are a new wave of popularity in the construction market. Condensation does not form inside such pipes at all, and therefore they very rarely need to be cleaned.
In its composition, vermiculite is close to aerated concrete, and is also light, but it does not absorb moisture at all, tolerates high temperatures and has good resistance to any physical influences.

Chimney cap
Many have seen at the end of the pipe something like an umbrella, fungus or cap. This part of the chimney is called the head, more modern terminology refers to this design as a spark arrestor, deflector.
The head of the chimney can perform either one or more functions - it protects against precipitation, extinguishes sparks flying out of the chimney, improves the draft of the stove, and sometimes it is a very beautiful decoration.
The head of the chimney can be structurally simple - in the form of an umbrella, or it can also have a complex design to protect against wind blowing and improve overall traction, the appearance in this case may have a different shape.

Chimney draft
There are special devices that measure the chimney draft in pascals (pressure difference in the sections of the chimney), although they are very expensive, so in most cases rather trivial methods are used to determine the draft:
- the traction force is set by the deflection of the sheet of paper (in most cases, toilet paper is the best fit);
- the direction of the draft is determined by the direction of the smoke from the lit cigarette.
Also, the sufficiency of traction can be determined visually:
- Smoke in the room - reverse draft;
- The flame is bright white, a hum in the chimney is possible - the draft is too strong;
- Flame with dark stripes, red - insufficient draft;
- The flame is golden yellow - draft is normal.
What determines the draft of the chimney:
- insufficient height will lead to a decrease in thrust, and in the case of excess, then, on the contrary, to an excessive increase. If you are not going to carry out an accurate physical and mathematical calculation, you should focus on a length of at least 4.5 meters.
- The shape of the section directly affects the aerodynamic characteristics of the chimney: in the case of a rectangular or square section, we get additional twists at the corners that prevent the overall flow, which is not observed in round counterparts.
- Placing the chimney mainly in the inner part of the building will allow you not only to increase the heating capacity of the entire heating system, but will also make it possible to maintain a constant good draft (even in frosty weather).

At the same time, the location of the chimney outside the building requires a longer heating and, as a result, will cause a decrease in draft.
- Too small dimensions of the cross-sectional area with the release of a large volume of combustion products will not create the necessary thrust. This rule is exactly the opposite: too large a cross-sectional area with small volumes of combustion products will lead to the fact that all the heat will “fly out into the pipe”. Installing chimney pipes of different diameters in different sections of the chimney will not only lead to unpredictable draft behavior, but will also allow the formation of soot and other deposits.

- It is best to place the chimney pipe closer to the roof ridge, but certain conditions must be observed here: if the pipe is at a distance of 1.5 meters from the ridge, then the head must rise at least half a meter. If the distance between the ridge and the head is in the range from 1.5 to 3 meters, then we place the chimney flush with the ridge. When the distance exceeds 3 meters, in this case, the head should be located on a line drawn at an angle of 10 degrees from the roof ridge down. Incorrect positioning of the chimney in relation to the roof ridge can lead to a weakening of draft in certain wind directions.
- Chimney draft also depends on the smoothness of the chimney walls, the presence of sharp turns.
- The shape and dimensions of the pipe head also affect the thrust. When assembling and choosing an umbrella, there is a significant risk of "miscalculating" the dimensions and, as a result, getting a reverse thrust, for example, if the umbrella is too large and lowered too low. In the case of installing a factory stainless steel chimney umbrella, there will be no problems - all the necessary parameters have already been calculated by engineers
- Atmospheric phenomena, air pressure, temperature, humidity, presence of wind - all this, of course, affects the draft in the chimney.
We can manually adjust the draft with the help of a gate.
A gate is a damper, the intended use of which is designed not only to regulate the traction force, but also to protect the room from fire. One gate is installed in the chimney channel, the other, as a rule, is mounted either in the furnace itself or in its door. Thus, by varying their position, we can adjust the traction force, which is an important plus.
A good stove and chimney are the key to warmth and comfort in the house, because with its help you can easily heat even a very large house.
However, not everyone can fold the stove and pipe correctly with their own hands, which is why in order to perform such work, you need certain knowledge and work experience. Laying a chimney with your own hands is not at all difficult, you just need to have all the necessary materials and follow the instructions.

We do not imagine homes without heating. Our concept of comfort unconditionally includes a suitable temperature regime. There is no central heating in a private house, and each owner has a heating problem.

We welcome our regular reader and bring to his attention an article about chimneys for stoves - an absolutely necessary component of any heating system, whether it is a stove, a modern fireplace or a boiler with automatic fuel supply.

Chimney - a vertically located pipe that discharges hot flue gases of the fuel in the heating unit into the atmosphere to a height sufficient to create draft in the duct and disperse toxic combustion products away from windows and ventilation ducts.

Principle of operation

The principle of operation of chimneys is based on the phenomenon of expansion of hot gases, a decrease in their density and, accordingly, the rise of lighter gases upwards.

Flue gases rise upwards, a rarefaction is formed in the furnace and colder air is sucked in - a draft phenomenon occurs.

How is the chimney

The main part of any chimney is a vertical pipe structure. Structurally different from modern prefabricated counterparts from prefabricated modules.

A traditional brick chimney includes the following elements: a neck for connecting to a furnace, a riser with valves, a slope, an otter, a neck (at the point of passage through the roof), a headband, and sometimes a metal cap.

Homemade chimneys made of metal or asbestos cement include pipes, caps, adapters for connecting to the furnace, and insulation.

The most modern types of chimneys are ceramic and made of. The ceramic structure consists of an external expanded clay concrete frame, an internal prefabricated ceramic pipe, and a layer of insulation between them. The ceramic and sandwich structures themselves include the following blocks: straight, for collecting condensate, tees, cleaning modules, transition elements for connecting heating units. An integral part of a modern chimney is a deflector.

Types and designs

The design features of the chimney primarily depend on the material from which they are made.

According to the material of the chimneys are:

• brick;
• reinforced concrete (usually industrial);
• asbestos-cement;
• of steel;
• ceramic;
• three-layer metal - two layers of steel with mineral wool insulation between them.

By design, chimneys are:

• indigenous - the design has its own foundation;
• wall, built into the bearing walls of the building;
• mounted - light pipes are mounted on a vertically located outlet pipe of a boiler or fireplace (and a potbelly stove);
• often lightweight structures are simply suspended from the supporting structures of the building;
• coaxial - arranged according to the "pipe in pipe" principle. The most common example is the horizontal gas outlets of gas heating boilers. It is used in devices with a closed combustion chamber and provides maximum safety for residents. Save fuel consumption. Recently, vertical structures of the Shidel system have appeared, taking air for combustion on the roof of the house (just below the head).

Which is better to choose

The choice of a chimney largely depends on the parameters of the installed heating unit (design, temperature, type of fuel used), the degree of readiness of the house (we are modernizing an old house with a stove and a wall pipe, the house is only “in the project” or the supporting structures have already been mounted, or there is already a finish) ; heated volumes.

Features of various types of chimneys are shown in the table:

Table 1

Name	Advantages	disadvantages
brick	Robust and high temperature resistant masonry construction, durability depending on the liner material.	Difficult installation requiring highly qualified masons; heavy weight, the need for a foundation; long installation time, the need to replace the insert approximately every 10 years. When working with modern boilers and fireplaces, a brick without an insert can collapse in just 10 years. Wall structures can only be mounted during the construction of the house.
Ceramic	Service life up to 50 years, smooth inner surface, high installation speed; high acid resistance, good thermal insulation; withstand temperatures up to 550°	Expensive option; installation requires some qualification, there is a need for a foundation; fragility
Steel single-layer (and asbestos-cement)	Smooth inner surface, light, inexpensive, fast installation, easy repair; resistance to corrosion and condensation	Requires insulation; when passing through structures made of combustible materials, large retreats are necessary; they burn out in 10-15 years, there are no components - during installation you will have to do all the elements yourself. Galvanized will last five years (or less)
Steel type "sandwich"	Long service life, smooth inner surface, light weight, quick easy installation, easy repair, high resistance to corrosion and condensation; can be installed / hung outside the building; good thermal insulation	Fairly expensive items.

It is not worth using flexible steel corrugation - they burn out very quickly.

Despite the price, it is worth choosing modern ceramic chimneys or "sandwich". If necessary, they can be mounted both in the finished house and outside the house, they are durable, easy to assemble, resistant to high temperatures, well insulated, and have a large assortment of ready-made factory elements.

If you want to use an old wall box from a conventional heating stove, you need to insert a stainless steel insert and insulate it. But perhaps you should choose a sandwich - less hassle.

Do it yourself or order

You can do it yourself some elements for the installation of single-layer pipes or lay out a brick structure (if you have the skills of a qualified bricklayer).

But the installation of prefabricated structures - this will help save a considerable amount from the family budget. You will have to pay a lot for the services of a qualified team - the amount is comparable to the cost of materials. There is a risk of running into unskilled workers.

When deciding whether to do the work yourself, you need to carefully analyze your capabilities:

• how accessible is the roof;
• Do you have friends or relatives who can help?
• do you have a fear of heights;
• What are your qualifications in performing repair work.

Building regulations

The arrangement of chimneys is determined by the provisions of SNiP 41-01-2003.

The design of the chimney must meet the following regulatory requirements:

• the minimum height must be at least 5,000 mm or grate;
• when located on a roof slope at a distance of less than 1.5 m to the ridge - the pipe must be 500 mm higher than the ridge;
• when located on a roof slope at a distance of 1.5-3 m to the ridge - the pipe must not be lower than the ridge;
• when located on a roof slope at a distance of more than 3 m to the ridge, the angle between the horizontal and the line passing through the ridge and the top of the pipe should be no more than 10 °;
• the head should rise above the flat roof to a height of at least 1,000 mm;

• the maximum length of each horizontal and inclined sections should not exceed 1000 mm, the total length of their projections on the horizontal should not exceed 2000 mm. In the presence of oblique and horizontal sections, it is necessary to lengthen the pipe by the length of the horizontal projections. For ceramics, the presence of horizontal sections is not allowed.

Fire safety requirements for chimneys

The distance from the surface of chimneys made of ceramic, insulated steel and asbestos-cement to combustible structures of the house must be at least 250 mm; for brick chimneys and sandwich pipe structures - at least 130 mm.

It is necessary to protect building structures made of combustible materials with cement or gypsum plaster over a grid of at least 25 mm thick.

If the roof covering can burn (roofing material, shingles, ondulin), or leaves and fluff can accumulate on it, a mesh spark arrestor should be installed on the head.

Remember that the quality of smoke removal depends on the life and health of your loved ones.

Traction force

Factors affecting traction force:

• pipe height;
• the state of the surface of the internal channel - the regularity of cleaning from soot, the roughness of the walls;
• the presence of inclined or horizontal sections. The presence of horizontal and inclined sections is undesirable, since the lengthening of the chimney is undesirable - the gases will cool, the draft will decrease up to tipping over;
• deflector installation;
• quality of insulation;
• air supply to the furnace.

Your safety depends on the traction force, therefore it is necessary to regularly check the presence of traction and take measures to clean the channel from soot, the pipe head from ice.

Making and installing a chimney with your own hands

What materials are better to make

The easiest to install are steel structures. Single-layer steel products require insulation and the manufacture of components - in general, work for pathological workaholics, and here we will not consider their installation.

Installing a chimney from a sandwich pipe is quite simple, the presence of a large number of various elements and components in stores allows you to assemble a device of any configuration.

Drawing and diagrams

Before starting work, determine the dimensions and draw a diagram or drawing - this will help to correctly calculate the required amount of materials and properly organize the work.

Size calculation

The height of the pipe is determined in accordance with the requirements of SNiP 41-01-2003, but should not be lower than 5 m from the grate. The diameter is taken equal to the diameter of the outlet of the heater.

Installation video

Watch our video - it will help you see all the intricacies of the assembly process.

Mounting Features

Installation starts from the stove or fireplace. The first starting element is mounted on the nozzle of the boiler or furnace. This element is not insulated for technological reasons (alt-free filler is melted and sintered into stone). All elements are designed in such a way that one of its ends has a smaller diameter and is inserted one into the other, as into a socket. One of the docking options is to slightly pull out the inner pipe, insert it into another inner pipe. Press down. Then lower the outer pipe with insulation along it, press it down. Fasten the connection with a crimp collar, tighten it with a bolt and nut. All joints must be sealed with sealant.

Then a tee is mounted, modules with a cleaning hatch and a condensate trap are mounted from below. There are designs for installing the lower part of the chimney on the floor.

Then mount the rest of the structure. After a meter, the sandwich is attached to the wall with special brackets. An element with a cleaning hatch should be installed on each floor and in the attic.

It is advisable to connect the elements of the chimney “through condensate” - the pipes are mounted in such a way that the upper one is inserted into the lower one and the condensate cannot seep through the joints, but flows down the walls into the trap.

An element with a gate is mounted under the ceiling.

The passage of the pipe in the ceiling is covered with a galvanized sheet and filled with insulation. The distance to the structures must be at least 130 mm.

The most difficult stage in the installation is the passage of the roof. Mark the hole in the right place on the roof. Make a hole in the roof. A roof sheet is attached from the inside, a roof cutting is installed on the roof. It is selected depending on the angle of the roof. The cutting edges lead under a sheet of roofing material.

If necessary, install extensions. Install deflector.

Common errors and installation problems

The most serious mistake is the lack of a condensate collector and elements with cleaning hatches.

In places where structures pass through ceilings, it is strictly forbidden to install joints of individual elements - leaking hot smoke can cause a fire.

A very significant mistake is the absence of a deflector or at least a cap over the chimney.

Snow and rain should not get inside the pipe - they increase the formation of condensate, ice can block the cross section of the pipe.

Maintenance and cleaning

Any chimney requires regular cleaning of soot. This will avoid fires, reduce traction. Cleaning should be done twice a year.

There are two cleaning methods - mechanical and chemical.

With a chemical fire, special agents are burned in the furnace. They burn at a very high temperature and accelerate the wear of the inner walls of the chimney, so it is better to use mechanical cleaning methods for a sandwich.

Icicles and frost from condensate can freeze on the head - they block the section of the box and reduce draft, which increases the risk of carbon monoxide poisoning for residents.

It is necessary to choose pipes in which the thickness of the outer metal layer is 1 mm (and not 0.5 mm). It is very easy to check - for a product with a thin wall, the wall bends if you squeeze it with your hands.

When installing sandwich structures, it is necessary to use a special sealant for high operating temperatures (automotive sealant with an operating temperature of 500 ° is not suitable).

If the pipe rises above the roof by more than one meter, it should be reinforced with stretch marks.

Of course, a modern house with a stove is an anachronism. A zealous owner puts himself a complex economical heating system.

However, what could be better than sitting in front of a fireplace on a cold evening or taking a steam bath in a Russian bath? But both a fireplace and a good stove in a Russian bath cannot do without chimneys and chimneys. This equipment will also be relevant in the construction of stationary barbecues and barbecues. The device of chimneys and chimneys is quite simple, but has some nuances.

Chimneys and chimneys can be divided into several large groups depending on the material of their manufacture. So they can be made using brickwork, from metal pipes of various types, as well as from multilayer materials.

In addition, stove chimneys may differ in the way they are installed:

• Wall chimneys are mounted directly in the thickness of the walls of the building, external or internal. At the same time, stoves and fireplaces can also be mounted directly in the walls of buildings.
• Suspended chimneys are mounted on the outer walls of buildings.
• There are also indigenous chimneys. Such structures are mounted separately, next to the furnace.

SNiP requirements for chimneys and chimneys

Certain requirements are imposed on chimneys and chimneys under construction by existing SNiPs:

• They must effectively remove combustion products.
• They must have sufficient height above the roof ridge.
• Their internal section should be sufficient for complete removal of smoke.
• Pipes must be resistant to high temperatures.
• They must be strong, the upper part of the chimney must withstand gusts of wind

Let's start with the height of the chimney. Sufficient height of the chimney provides good draft and effectively removes combustion products, preventing the room from smoking and maintaining draft. However, excessive pipe height can lead to condensation and reduced draft.

The diameter of the chimney or its internal section is calculated based on the dimensions of the furnace. It increases along with the volume of the furnace space, in proportion to it. An insufficient section of the chimney leads to smoke, but an excessive diameter will, on the contrary, lead to a decrease in traction.

What should the chimney be made of, what materials are prohibited to use?

The main requirement for the material for the manufacture of chimney chimneys is heat resistance. The minimum fire safety threshold for chimney material is set at 30 minutes and 1000 degrees. In continuous operation, the pipe material must withstand temperatures of 500 degrees without damage, since the temperature of the combustion products rarely drops below 300 degrees.

A margin of 200 degrees is due to the fact that soot accumulating in pipes tends to ignite spontaneously.

Strict requirements are also imposed on thermal conductivity. The temperature of the outer layer of chimney pipes should not exceed 90 degrees, and in places of interface with flammable structures - no higher than 65 degrees.

We especially note that the combustion materials have an aggressive chemical composition and the material from which the pipes of furnace chimneys are made must effectively withstand an unfavorable chemical environment. In addition, the part of the pipe that extends outside the room is exposed to climatic conditions and must not be destroyed due to temperature changes.

The traditional material for the manufacture of chimneys is refractory bricks. It almost perfectly meets all the requirements for chimney materials. However, the construction of brick chimney chimneys requires certain skills.

In addition, the brick must be individually selected for each heating device. So in furnaces, the temperature of the combustion products is usually kept at 250 degrees, but in fireplaces, under direct fire conditions, it can reach 400 degrees. Thus, the walls of a brick pipe for a fireplace are recommended to be made of fireclay bricks, laying a wall thickness of more than 15 centimeters with 5 mm seams. This significantly increases the cost of manufacturing chimney pipes for fireplaces, as well as the requirements for the strength characteristics of the foundations under the fireplace.

Asbestos cement chimneys and chimneys

Relatively cheap, but also reliable material for the manufacture of chimney pipes are asbestos-cement pipes. They can be used for the construction of chimneys in stationary barbecues, light buildings, baths. When installing such pipes, special attention should be paid to areas of interface with flammable materials, since an asbestos-cement pipe may crack during service.

Stainless steel chimneys

As a rule, furnace chimneys made of stainless steel can be used in the construction of heating systems with gas boilers. Such a pipe heats up very strongly from the passage of combustion products and therefore it must be reliably equipped. In addition, it is necessary to pay special attention to the quality of the pipe from which the chimney is made. Thin stainless metal, especially in low-quality pipes, can crack, which can easily cause a fire.

Also, the disadvantage of this model of pipes is the strong formation of condensate on their surface.

Pipes and chimneys made of multilayer composite materials

New models of pipes, also called "sandwich pipes", appeared on the market relatively recently, but have already managed to prove themselves well. Multilayer pipes are manufactured in industrial conditions, usually in the form of meter lengths; during installation, the chimneys simply need to be connected. Such a pipe is reliable in terms of strength, is highly resistant to high temperatures and to aggressive chemical environments.

Usually sandwich pipe has three layers. The inner surface is made of stainless steel, the upper surface is galvanized. An insulating material is placed between them.

Such a pipe has a small weight and is quite undemanding to installation. It does not give a big load on the furnace. As a disadvantage, one can note the high cost of such structures and a relatively low service life. However, the time of trouble-free operation of a sandwich pipe depends on the specific manufacturer. During operation, such a pipe is subjected to temperature deformations, which can violate its integrity.

Multilayer pipes may have a different composition. So the inner part can be made of refractory clay, and basalt wool can be placed between it and the upper shell of lightweight concrete. Such a complete set of multilayer pipes significantly increases their service life. In addition, various decorative coatings can be glued to the outer part of such a pipe.

Modular chimneys

Modern industry offers ready-made kits for self-installation of chimney chimneys. All components are produced in industrial plants and then easily assembled on site.

How to arrange a chimney passage through the roof?

1 - chimney chimney, 2 - rafter leg, 3 - fireproof heat-insulating material, 4 - load-bearing beam

Typically, the installation of chimney chimneys is carried out during the construction of a building or structure, simultaneously with the installation of a stove or heating system.

With this approach, you can easily adjust the relative position of the rafters under the chimney and create the necessary gaps between the wooden materials and the chimney. They must leave at least 15 centimeters and are laid with fireproof material, such as basalt wool.

When building a stove or fireplace, when calculating their foundation, it is necessary to take into account the weight of the chimney pipe.

The upper part of the pipe can be equipped with a protective device that prevents, on the one hand, the scattering of sparks, and on the other hand, the ingress of rain into the pipe.

Brick chimney laying - instructional video

In everyday life in any province, stove-makers offer several types of chimneys:

Stainless steel chimneys
- Ceramic chimneys
- Brickwork chimneys
- Chimneys from asbestos pipes

For consumers, stainless steel chimneys for stoves are the most inexpensive, reliable and convenient solution for smoke extraction. If you look at asbestos pipes, then their only plus is only the price. And the sea of ​​minuses, firstly: asbestos is harmful to health, harmful substances are released at high temperatures. Secondly, these pipes are not intended for smoke removal, it is very difficult to make a non-linear chimney. Thirdly, they are not durable.

Ceramic chimneys are extremely expensive and durable, and for such a chimney it is necessary to fill in a special foundation, the weight of one block is more than 25 kg, and there can be more than five dozen of them in the design, such a load will be a big problem for the floor. A brick chimney is also not a cheap solution, the overall design is heavy due to the complexity of the chimney, problems often arise when igniting the stove.

Stainless steel chimneys for stoves features

The main advantages of chimneys made of stainless steel:
- Large selection of metals for the chimney - no need to overpay for the material if you do not need a chimney for a large thermal and chemical load.
- more than 30 manufactured elements will allow you to assemble a chimney of any design
- the chimney structure to the stove is light, no additional foundations are needed
- a stainless steel stove chimney is much cheaper than brick and ceramic ones.