Installation of sandwich chimney in a private house

Having a dependable heating system is essential for keeping our homes warm and comfortable during the winter. In order to ensure adequate ventilation and the effective removal of smoke and gases from our homes, a chimney is essential. Sandwich chimneys are more common to see installed by homeowners these days because of their strength, efficiency, and attractive appearance.

An insulating layer is positioned between two layers of stainless steel to create a sandwich chimney. The chimney’s durability and thermal efficiency are both increased by this design. Sandwich chimneys are a sensible option for contemporary homes since they are lightweight and simple to install in contrast to conventional masonry chimneys.

Beyond its practicality, installing a sandwich chimney in a private home has many benefits. Sandwich chimneys’ sleek and contemporary design elevates any house’s overall aesthetic appeal by lending it an air of refinement. In addition, these chimneys require less upkeep than conventional alternatives, which ultimately saves homeowners money and time.

Sandwich chimneys’ superior insulation qualities are one of their main advantages. Better temperature control within the house is made possible by the insulating layer that sits in between the stainless steel walls and helps to retain heat. Sandwich chimneys are an eco-friendly option because of this, which also increases the heating system’s efficiency and lowers energy usage.

Rules of flue duct construction

The general fire safety regulations must be followed when building a sandwich-style chimney, as they are applicable to all flue duct types—brick, asbestos, and ceramic. Inaccurate pipeline installation poses a serious risk of fire, particularly in wooden cottages with chopped, framed walls.

Think back to the modular sandwich design. Sections that are straight and shaped are composed of 0.5–1 mm stainless steel pipe that has been covered in a layer of non-flammable insulation (basalt wool or kaolin, 25–100 mm thick). A protective 0.5 mm stainless steel or galvanized steel casing surrounds the exterior.

Depending on the kind of heating equipment, the chimney device’s requirements vary somewhat. The cause is the disparity in temperature between the combustion products at the heat generators’ output:

• atmospheric gas boiler – maximum 200 °C, working boiler – about 120 degrees;
• natural gas condensing heaters – 120 and 80 °C respectively;
• solid fuel boilers on wood, pellets – up to 300 degrees, on coal – 500…700 °C (maximum);
• fireplaces and fireboxes – 350…650 °C;
• bath stoves – up to 700 °C;
• liquid-fuel (diesel) units – 250 °C.

Due to their high efficiency of 88…96%, gas and solar heat generators have low smoke temperatures at the outlet. However, a significant amount of condensate is produced, which must be emptied. Because they are more heated and soot-filled, the chimneys of wood-fired boilers and stoves present a greater risk of fire.

Note: A coaxial chimney, or double channel of the "pipe in pipe" type, organizes the gas discharge from condensing and turbine units. Not applicable to modular sandwiches.

Gas and diesel boilers flue ducts

The following guidelines should be followed when installing a sandwich chimney for gas-fired heating units:

1. The minimum height of the pipe elevation is 5 meters, the optimal height is 6 meters. We start counting from the working surface of the burner.
2. The chimney head must not be located in the area of wind support, which is formed near the ridge of a gable roof or a tall building standing next to it. To ensure that the natural draught works well, install the chimney according to the diagram below.
3. The diameter of the inner passage of the sandwich is selected according to the size of the boiler outlet pipe. It is inadmissible to install a chimney with a smaller cross-section.
4. The maximum length of the horizontal section connecting the heat generator with the vertical shaft of the sandwich chimney is 3 meters;
5. The permissible number of pipeline turns by 90° is 3.
6. The vertical channel can envelope the supporting structures of the roof – rafters, beams, when installed outside – roof overhangs. Maximum deviation – 1 m to the side, the angle of rotation of the sandwich – 30 or 45 °.
7. At the bottom of the vertical section provides a pocket for the collection and drainage of condensate.

Crucial! Gas heater chimney pipes shouldn’t be covered with any kind of deflectors, umbrellas, or other accessories.

The passage through a combustible wall or ceiling presents a different problem. The following are the requirements for fire protection: there must be at least 38 centimeters between the sandwich pipe’s inner wall and the closest wooden structure. Passage openings are indented with the designated amount.

Requirements for stove chimneys

The temperature of the chimneys of solid fuel boilers, stoves, and fireplaces is higher. When heating with raw wood, condensation forms and soot accumulates inside. The latter combines with sediments to create a thick, sticky deposit that is challenging to remove.

When a thick layer of soot ignites, the shaft can get as hot as 800-1000 °C. As a result, increased temperature of combustion products and maintenance (cleaning) are considered when installing the chimney.

Citation. Sandwiches can tolerate overheating to 1000 °C for a short while. Because basalt insulation operates between 600 and 750 degrees Celsius, minwool is destroyed by frequent emergencies. The inner sleeve’s stainless steel is also distorted, occasionally rupturing at the seam.

Guidelines for placing a sandwich from a TT boiler or wood stove:

1. The above requirements for trunk height, gas duct diameter and number of bends remain in force.
2. The horizontal connecting section is made as short as possible, preferably within 40 cm. This is where a lot of soot accumulates, so it is important to provide a cleaning option.
3. A 250 mm deep condensate pocket is required for solid fuel boilers and metal heating stoves. It also serves as a manhole. Exception – sauna heaters with high gas temperature and fireplaces connected directly to the vertical chimney.
4. Bypass the supporting structures of the roof is allowed, but unnecessary turns should be avoided or made at an angle of 15-30 °.
5. The top cut of the pipe may be covered with a hood. But if there is a condensate collector umbrella is better not to put the umbrella, let precipitation unnecessary flush the channel from soot.
6. Immediately behind the boiler or steel stove, a gate valve must be installed, if not provided by the design of the heat generator.
7. Stove penetrations in wooden ceilings are mandatory. The distance from the inner sleeve of the sandwich to the combustible construction or finish remains the same – 38 cm.

Important point. Section gaps should be filled with non-flammable insulation such as kaolin wool, stone, or basalt cardboard. Connecting pipelines at the floor slab intersection is prohibited.

Certain manufacturers (like Schiedel) specify in their installation manuals that there must be a 20 cm gap between the sandwich pipe’s outer wall and any combustible ceiling or wall structure. Although the indication does not follow widely accepted guidelines, you alone are accountable for any consequences in your own home. Soot buildup, shoddy sandwich construction, and improper installation can all cause a fire.

If the transition from brick chimney to sandwich chimney needs to be organized inside the house, the diameter is chosen as follows:

• fireplace – 8 cm² of cross-section for each kilowatt of heat output;
• Wood stove with a heat output of up to 3 kW.5 kW – 0.02 m² = Ø160 mm;
• the same, up to 5.2 kW – 0.028 m² = Ø190 mm;
• stove with a capacity of 5.2…7 kW – 0.038 m² = Ø220 mm.

Minimum 50 cm should separate the top of the connecting sandwich from the wooden ceiling; this distance should be 40 cm when protected by a metal sheet and basalt cardboard. Cutouts and indentations are not necessary in brick homes with concrete ceilings.

Sandwich installation diagrams

Three methods exist for creating a chimney out of modular sandwich pipes:

1. The vertical part is located on the street, fixed to the outer wall of the building. Horizontal chimney crosses the outer fence, enters the house and is connected to the boiler (furnace) spigot.
2. The vertical flue runs through the roof, descends into the boiler room and ends with a condensate collector. The heat generator is connected to it by a horizontal pipe.
3. The trunk again crosses all roof structures, but it is connected to the heater directly, without a pocket and horizontal sections.

Note: Although there are numerous methods for installing chimneys, they are all variants on the schemes mentioned above.

The first choice is appropriate for prefabricated homes of any kind, including brick, frame, and log homes. It is your responsibility to position the boiler against the outer wall, guide the sandwich outside, and then repair the main pipe. This method of installing the chimney is the most cost-effective in terms of both labor and money.

According to the second scheme, installing a modular system is considerably more difficult. A single-story home’s roof slope and ceiling must be passed, setting up areas for fire safety. The piping in a two-story house will enter the space and prompt you to consider decorative cladding. However, you won’t have to use stretchers to secure the chimney’s end and avoid the roof overhang.

The final version works well with fireplaces and sauna stoves. The first ones practically never condense due to their strong heat, while the second ones are concealed by the fire-resistant gypsum plasterboard finishing. Ventilation is included in the gap between the pipe and the lining to facilitate the cooling of the sandwich channel. Convection grids, seen in the above image, are used to extract heated air from beneath the fireplace furnace’s lining.

It makes sense to install a sandwich chimney in a private residence to increase efficiency and safety. These chimneys have insulation between the inner and outer layers, which lowers heat loss and lowers the possibility of a fire. Sandwich chimneys shield the building from potential damage and enhance indoor air quality by efficiently directing smoke and gases out of the house. Furthermore, compared to conventional chimney setups, their modular design ensures a quicker and more seamless installation process. Sandwich chimneys not only provide homeowners with peace of mind but also a dependable solution for their heating needs because of their durability and low maintenance requirements.

Elements of modular systems

It is vital to comprehend which parts go into a two-circuit chimney in order to design an installation plan, buy parts, and assemble it later. Let’s enumerate the key components, with images:

• straight sections of sandwich pipes with lengths of 25, 50, 100 cm;
• 45°, 90° tees;
• 90, 45, 30 and 15 degree elbows;
• Transitions from single-wall chimney to double-circuit chimney – "start sandwich";
• Rotary flaps (dampers);
• condensate collectors and various headers;
• ceiling passage units (abbreviated as PPU);
• support platforms, brackets;
• fasteners – crimp clamps, under stretching;
• elements of pitched roof sealing called master-flush or "kryza";
• end caps, skirts.

Note: This is a partial list of parts for chimneys. There are floor stands, revision hatches, crosses, and straight channels with revision and condensate drainage.

The socket-profile jointing technique joins double-layer pipes with other pieces. The relationship is referred to as "tongue-and-groove" or "daddy-mommy" by the mother, who finds it endearing. Every shaped part (apart from end pieces) has a groove on one side and a spike on the other during manufacturing.

We recommend, as an illustration, looking at the wall sandwich chimney assembly plan, which begins at the boiler:

1. To the outlet of the heat generator through a coupling connect a single-wall pipe, then mount the starter adapter to the sandwich pipe.
2. Connect the straight section of the double-layer pipe to the transition point, which goes out to the street. There it is inserted into the tee.
3. Below the tee we place the revision section, then the support pad and the condensate collector. The structure is mounted on the wall bracket.
4. From the tee, we climb straight sections, every 2 meters we fix to the wall with sliding brackets, the joints of the elements are clamped with clamps.
5. At the end of the chimney we install a cone without an umbrella (for a gas boiler), a simple cap or a deflector.

Note: In accordance with fire safety regulations, a square opening must be cut out and the FPU installed if the horizontal chimney crosses a wooden wall.

In cases where avoiding the roof overhang is imperative, we employ two 30- or 45-degree bends. As seen in the above photo, secure the chimney’s end with stretchers to stop it from swaying in the wind. Watch the video for an example of professional sandwich pipe installation for a steel stove:

Instructions for assembling the chimney

Thus, a good laying plan has been chosen, and supplies have been bought. Make the following arrangements prior to flue duct installation:

1. Lay the route of the future gas duct. Make sure that when crossing the wall or ceiling, the pipeline did not fall on load-bearing structures – the posts of the frame house, roof beams, rafters.
2. Install the boiler or furnace. Here it is important to choose the right place so that the chimney does not turn more than 2 times (the third turn is the entrance to the tee).
3. Protect the combustible lining of the ceiling and walls adjacent to the heat generator from fire. Use galvanized sheet + basalt cardboard, minerite boards or other fire-resistant materials.
4. Make a passage hole in the outer wall or ceiling (depending on what scheme you have chosen).

Initially, attempt to put the chimney pieces together on the ground in accordance with the designed plan. Verify that every component and fastener is available.

Important nuance. Chimney sections are frequently jointed using high-temperature stove sealant. The modules can only be cut with a bolt cutter once the compound has solidified. Once more, Schiedel advises using clamps instead of sealant when assembling the chimney pieces.

How to build a sandwich chimney correctly using your hands:

1. The chimney should not load the boiler with its own weight. Fix the supporting parts – floor stand, wall brackets. Remember to keep clearances for combustible structures, move the pipe to a safe distance. For plastered brick or concrete walls the interval is minimum – 50 mm.
2. Assemble the ceiling assembly (FPU). To prevent the metal box from touching the wood, lay strips of basalt cardboard at the joints. In the inner cavity of the box, put basalt insulation when you run the pipe.
3. Start the installation of the gas duct from the heat generator. Install the coupling, a section of regular stainless steel pipe, then move on to the sandwich pipe.
4. The correct pipe connection is "condensate". The socket of the upper section (mom) is put on the lower one (dad). The metal extrusions on the sandwich will cover the joint from both sides, then condensate inside the channel and precipitation from outside will safely flow down the walls.
5. After connecting the neighboring modules, the joint is additionally crimped with a special bandage. Do not confuse it with fastening clamps.
6. The tee with inspection and condensate drain can be assembled on the ground, then connected to the horizontal chimney and supported on a bracket.
7. Further installation of the sandwich pipe is carried out from bottom to top. Every 1.5…2 m trunk is fixed to the elements of the building that can withstand the weight of the chimney. Cover the upper cut with a suitable nozzle to protect the insulation from precipitation.
8. The channel laid through the roof is sealed with a "cap", whose upper edge is inserted under the roof covering, the lower edge remains on top. Additionally, a skirt is placed over the "roof" to cover the gap around the pipe.

Remind yourself. The two elements’ connection cannot be made inside the wall, in the FPU. Any type of structure is prohibited, including ones with no flammability.

In order to prevent wind swaying, ties should be used to secure flue ends that are elevated more than 1.5 meters above the final attachment point. Making a square or triangular mast out of steel angles is an additional choice. Using the standard fasteners, the chimney is installed inside the lattice tower.

The efficiency and safety of your heating system can be greatly increased by installing a sandwich chimney in your home. Sandwich chimneys reduce the risk of fire and carbon monoxide poisoning by establishing a sealed pathway for smoke and gases to leave your home. Their insulated construction also aids in maintaining ideal temperatures, minimizing heat loss and raising your heating system’s overall effectiveness.

Sandwich chimneys’ adaptability is one of their main benefits. They can be put in a variety of homes, even ones with odd floor plans or constrained spaces. There is a sandwich chimney solution to fit your needs, regardless of whether you have a wood-burning stove, a modern gas boiler, or a traditional fireplace.

Sandwich chimneys also require little upkeep and are long-lasting. Because they are made of premium materials like ceramic insulation and stainless steel, they can withstand the hard use and bad weather. A sandwich chimney can provide dependable ventilation for your heating system for many years with correct installation and sporadic maintenance.

Consulting with qualified experts is crucial when thinking about installing a sandwich chimney. An experienced chimney technician can evaluate the unique needs of your house, suggest the best chimney system, and make sure it’s installed securely and correctly. You can have peace of mind knowing that your heating system is working effectively and that potential dangers are kept out of your home by leaving the installation to the professionals.

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