Types of thermal insulation of chimneys

The products of combustion of fuel in a stove or fireplace are removed from the room using a chimney. Chimneys have a complex structure. To obtain the necessary traction, it is necessary not only to correctly calculate their height, to carry out a competent installation of the chimney, but also to properly organize thermal insulation. There is a wide choice of heaters for insulating pipes of all types of stoves and fireplaces.

Why is thermal insulation needed?

One of the important reasons is fire safety. Flue gases can have temperatures up to 400 degrees. An overheated chimney often causes a fire. Therefore, it is especially carefully isolated at the points of contact with the structures of the house: ceilings, roofs, walls.

The second reason for the insulation of the chimney is the fight against condensate. Water vapor impregnated with combustion products cools and settles in the form of a resinous liquid on the inner walls of the chimney. The substance not only clogs the pipe and reduces its permeability, but also corrodes its walls. Another negative consequence is an unpleasant odor that enters the living space from the chimney.

The formation of condensate is especially intense in winter, when there is a big difference between the temperatures outside and inside the chimney. This is one of the main causes of condensation. Therefore, thermal insulation of the chimney is an important step that will significantly extend its service life.

The most popular types of heaters

Often, the thermal insulation of chimneys is done by hand. In this case, the main attention is paid to the section of the chimney, which is located outside the heated zone. That is, the part of the chimney that is on the roof is insulated. Sheet insulation is stuffed or glued onto brick pipes, and when insulating round metal pipes of wood-burning stoves, a “sandwich” type construction is used. Most often, stone and mineral wool, polyethylene foam, and kaolin fabric are used to insulate chimneys.

Teploizol

It is molded polyethylene foam. It is made in the form of pipes of different diameters, can be used without additional operations for cutting, winding, tying. Also sold in sheet form.

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Advantages:

• no shrinkage;
• seamless;
• does not absorb moisture;
• vapor tightness;
• long service life.

Folgoizol

May consist of two or three layers. One is polyethylene foam, the second is foil. The third layer is made of either foil or polypropylene.

Advantages:

• light weight;
• high heat-reflecting properties due to the use of foil;
• there is no moisture absorption;
• simple installation;
• safe for humans.

The cost is higher than that of thermal insulation, but its protective properties are also better.

Basalt wool

Made on the basis of basalt fiber. Synthetic resins are used as a fixing agent. Modern manufacturing technologies make the material as safe as possible.

Advantages:

• low thermal conductivity;
• incombustibility;
• long service life;
• high strength;
• good soundproofing properties.

glass wool

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Time tested material. It is made from cullet, soda, sand, borax, limestone, dolomite are also used as raw materials — the same that is used to make glass. Polymer components are used as a binder for fibrous material.

Advantages:

• withstands temperatures up to 450 °C;
• has low thermal conductivity;
• high strength;
• good soundproofing properties;
• incombustibility.

Kaolin

Natural material that is mined in special deposits. Another name is white clay. It is used in the form of non-combustible kaolin wool — thermal insulation, which is suitable for all types of chimneys.

Advantages:

• does not emit harmful substances when heated;
• refractory material;
• electrical insulating material;
• low thermal conductivity;
• resistance to high temperatures;
• high chemical resistance.

Recommendations of experts on the choice of insulation

There is a wide range of thermal insulation materials. The quality of the insulation depends on its thermal conductivity and thickness. The thicker the insulation and the lower its thermal conductivity, the better it will insulate from unwanted heating or cooling. When choosing a heater, you need to pay attention to fire resistance, heat resistance, and the absence of toxic emissions when heated.

Kaolin wool has no competitors in terms of fire resistance. Even an open fire does not take it. The only drawback is the high price.

Basalt, mineral, glass wool are excellent heat-insulating heaters. They are not flammable. Previously produced brands were not completely safe for humans. Claims were caused by both a binder — phenol-formaldehyde resins, and crumbling hard fibers, the smallest particles of which could get into the respiratory tract. It is believed that modern production methods have completely solved the safety problems.

Advice! When laying insulation in several layers, it is necessary to overlap the heat insulator, avoiding overlapping joints.

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The safest materials: thermal insulation and foil insulation based on polyethylene foam. They have low thermal conductivity and are easy to use. Folgoizol better reflects thermal radiation, so it costs a little more. Ease of installation due to the shape of the product. It is enough just to put them on the insulated product, firmly fix it with aluminum tape. The disadvantage of the material is low heat resistance. Suitable for use at temperatures up to 170 °C. Also, there is no resistance to open fire.

How to install a heater with your own hands

Installing a heater is not a complicated procedure, it is easy to do it yourself. Before starting work, you need to understand what method of insulation will be used. It depends on the type of chimney, the design of the building and the funds that are planned to be spent on the thermal insulation of the chimney.

A reliable way of warming is bulk. A special box is mounted around the chimney. Kaolin, expanded clay, sand, slag and other heat-insulating materials are poured into it. The method is highly reliable: the structures are strong and durable. The used heaters are not combustible, resistant to high temperatures. The properties do not deteriorate over time, which allows you to reliably isolate the chimney. The main disadvantage of this method is the high labor intensity. The box is recommended to be installed at the stage of building construction. Otherwise, serious alterations may be required, which will entail high costs.

Insulation, type «sandwich»

The most popular method of chimney insulation is «sandwich». Rolled or sheet products made of basalt, glass or other mineral wool are used. The “sandwich” is formed as follows: the bottom layer is the chimney itself, the outer one is an additional iron sheet, the “filling” is the insulation layer. The gap should be chosen on the order of 4-5 cm. That is, the diameter of the outer pipe should be 8-10 cm larger than the diameter of the inner one.

The operating procedure is as follows:

• Pre-assembly of the vertical section.
• A heater is laid out next to the assembled chimney, it is desirable that the length of the roll matches its height.
• The chimney must be placed on top of the insulation.
• The heat-insulating material is fixed with adhesive tape. One end is fixed before the whole structure is placed in a large diameter pipe, which will become the outer layer of the “sandwich”. The other end is when the entire chimney is placed in a wide pipe.
• The last stage is the installation of the chimney. It is necessary to fix it to the wall, make a joint with the roof on the roof.

Advice! Reliable fastening of the chimney is provided by special brackets. They can come in a kit, bought separately, independently made from a corner.

Also, mineral wool can be fixed to the chimney simply with a wire or metallized tape. But even in this case, it is necessary to close the outer layer with a non-combustible material. You can use roofing material, refractory fabric, aluminum foil for winding. Protection from the outside will help extend the life of the insulation.

The use of polymeric materials as a heater

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The shape of thermally insulating products made of polymeric materials, including foamed polyethylene, makes it easy to install insulation.

The detachable structure is called the «shell», as it fits snugly around the chimney. Its main advantage is ease of installation. Well suited for warming a round metal chimney. The disadvantages include the need for individual selection of products according to the diameter of the chimney.

A «shell» is produced from polyurethane foam and polystyrene, it is not suitable for chimneys, as it does not withstand temperatures above 100 ° C. Similar polyethylene foam products are used at temperatures up to 170-180 °C. If basalt or mineral wool is used as the material, then such a product can withstand heating up to 400-450 ° C.

Waterproofing

To ensure that the insulation is not exposed to precipitation and is protected from the negative effects of the environment, it is necessary to install waterproofing. It is mounted on top of the roofing materials of the roof and is an apron made of waterproof material. After fixing the waterproofing, all joints must be carefully coated with bitumen, liquid rubber or silicone sealant. There are other ways to waterproof.

Fire insulation

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Heating chimneys to high temperatures causes additional requirements for their design. Especially true for chimneys organized in wooden houses. All points of contact with building structures must be carefully insulated to avoid overheating and ignition.

All of the methods described above are suitable for isolation. They can be insulated with asbestos cloth or cardboard. The use of asbestos pipes, the installation of ceramic chimneys will reduce the risk of fire. Cardinal ways to solve the problem: bringing the chimney to the street and using a pipe made of red refractory bricks.

Thermal insulation of brick pipes

Even if the pipe is made of refractory red brick, it still needs to be insulated. The easiest, fastest and most reliable way is plastering. From 3 to 5 layers of plaster are applied, while the total thickness should be about 40 mm. To keep the layers firmly, additional reinforcing elements are applied. They are installed separately on each layer of plaster.

To insulate a brick pipe with mineral wool, a crate made of a metal profile or a wooden beam is mounted on it. Sheet insulation is installed tightly enough to eliminate any gaps. Cotton wool is covered with a layer of vapor barrier, the joints are glued with adhesive tape. The final stage is finishing. You can apply plaster or sew up with polymer siding.

No matter how simple the measures for warming the chimney may seem, you should first carefully study all the necessary information. It is necessary to pay great attention to the choice of a heat insulator. It is required to think over in advance the order of work and prepare tools, materials, organize free access to the chimney or to the place of its installation.