The fireplace and chimney must be coordinated. For this reason, it is worthwhile to install a complete chimney system, especially in new buildings, in order to make optimal use of today's technical possibilities and at the same time maintain flexibility with regard to future developments on the fuel market. All components of a chimney system come from a single source and the manufacturers offer a variety of variants that are tailored to different fireplaces. Technical differences between the systems can be seen, for example, in certified properties such as moisture insensitivity or soot fire resistance.
A chimney system is a chimney system whose components are compatible with each other and which are offered by a manufacturer as a complete system. The manufacturer assumes product liability for the entire system.
The systems are delivered to the construction site as individual parts and assembled on site or used as floor-to-ceiling variants in full assembly in the shell construction. In this case, all components are pre-assembled in the manufacturing plant, only the floor-to-ceiling elements still have to be connected to each other on site.
When planning an exhaust system, not only technical construction knowledge is important, but also a feeling for future developments in this sector in order to advise the client correctly. It is difficult to predict today how the various fuel prices will develop and how high the future energy building standards will be.
A certain degree of flexibility in planning is therefore sensible, with regard to possible future developments. This could be, for example, the possibility of converting the fireplace to a different fuel or the simultaneous use of several fireplaces within a building, such as a gas boiler and a pellet stove.
for planning: For general requirements in planning, such as the minimum distances to combustible components or the location of the chimney mouth above the roof, the Combustion Ordinance FeuV of the respective federal state and the Federal Immission Control Ordinance BImSchV must generally be applied.
From a technical point of view, DIN V 18160-1 is of primary interest to the planner of exhaust systems. Despite its status as a pre-standard, it forms the basis for the planning, execution and acceptance of the exhaust system in Germany, together with Supplements 1-3 and DIN 18160-60 .
The harmonized DIN EN 15287 is the counterpart to DIN V 18160-1 at the European level, but still receives little attention in practice in Germany. There are also a large number of supplementary regulations for subcomponents of exhaust systems.
Chimney, how it works: In general, chimneys use the natural buoyancy of the lighter and hot exhaust gas produced during combustion in the fireplace. The resulting vacuum in the vertical exhaust pipe of the chimney causes a continuous upward pulling effect, which at the same time prevents the exhaust gases from entering the living spaces. How large this vacuum is depends heavily on the geometric conditions of the chimney, such as chimney diameter and chimney height, but also on the level of the flue gas temperatures. The higher the flue gas temperature and the smaller the chimney diameter, the higher the vacuum and thus the better the "draught" in the chimney.
If a chimney system is operated with overpressure, the exhaust gas is pushed into the exhaust pipe by means of a blower. This may be necessary if the exhaust gas temperatures are so low that the natural buoyancy is no longer sufficient to transport the exhaust gas out of the chimney. This is particularly the case with fireplaces that are operated with low-temperature or condensing technology. The gas-tightness of the exhaust pipe is important here.
Chimney, internal or external: If a house is planned, it must first be clarified whether an internal chimney system with a casing stone or an external chimney made of stainless steel is suitable for the construction project.
While one builder sees an external chimney as a design accent, another rejects it on principle because of its appearance.
Advantages of an internal chimney with a solid outer shell:
Advantages of an external chimney without a solid outer shell:
Location in the building: In principle, the chimney in the building should be guided exclusively vertically, i.e. without oblique distortions.
The location near the ridge is expedient due to static advantages. The area exposed to wind is reduced here, as the chimney does not have to protrude so far from the roof surface. In addition, there are often problems with the draught effect when it is located near the eaves, as winds blowing over the ridge can press into the chimney. Likewise, the location within the roof construction should be taken into account at an early stage in the planning. In the case of wooden roof trusses, the minimum distances to combustible components must be observed. See encyclopedia article ► Flue system, distances to combustible components in accordance with MFeuV
With a central placement in the building, it is also possible to connect fireplaces on all four sides.
Fire protection: A chimney must be made of non-combustible materials. Solid fuels in particular can reach particularly high exhaust gas temperatures. There is a risk that organic deposits in the chimney pipe will ignite and soot fire with temperatures of around 1000 °C will occur in the chimney pipe. It must be ensured that adjacent materials made of or with combustible materials cannot heat up to such an extent that a building fire occurs due to high temperatures inside the chimney.
In this context, distances or thermal insulation must be used to ensure that at exhaust gas temperatures of 400 °C, adjacent surfaces inside the chimney that consist of combustible or partially combustible materials cannot heat up above 85 °C in normal operation and not above 100 °C in the event of a soot fire. This is ensured by maintaining the prescribed minimum distances to combustible components. See encyclopedia article ► Flue system, distances to combustible components according to MFeuV
According to DIN V 18160-1, the chimney system must meet a fire resistance period of 90 minutes or longer in the event of an external fire. This ensures that a house fire cannot spread via the chimney to other floors.
If exhaust systems in buildings of building classes 1 and 2 are connected to fireplaces that are operated exclusively with gaseous or liquid fuels, a fire resistance period of only 30 minutes is required.
However, in order to be flexible in the long-term choice of fuel for a fireplace, it is always advisable to maintain a fire resistance period of 90 minutes in the planning.
Fire flashover over the chimney:
See also encyclopedia articles ► Flue system, fire resistance classes and ► Flue system, multiple occupancy
Thermal insulation: In the case of exhaust systems, the Energy Saving Ordinance (EnEV) must be observed. Systems that do not draw their combustion air from the boiler room or a supply line through the outer shell are particularly suitable in this regard. Chimney systems with insulated exhaust pipes and combustion air supply lines can also be used to implement high energy standards.
Stability: The stability of a chimney must be proven in accordance with DIN V 18160-1. The chimney shaft will be bricked up throughout and specially founded. If a basement foundation is not possible, e.g. if the shaft is not led to the basement due to subsequent installation, some manufacturers offer systems with particularly light mantle block variants, e.g. made of lightweight concrete. In any case, the shaft must stand on a fireproof surface.
In accordance with DIN V 18160-1, false ceilings can serve as lateral support for the chimney shaft. This is considered fulfilled if the joint between the ceiling and the shaft is not wider than 2 mm. The vertical expansion of the shaft must remain possible. At least every 5 m, a chimney shaft must be supported laterally, whereby it must not be higher than 3 m above the uppermost support and at the same time not higher than 5 times the smallest shaft width.
In the area of the roof truss, the chimney is not sufficiently supported by false ceilings. Here, due to the high wind load over the roof, the bending stiffness of the chimney shaft must be achieved by reinforcing the mantle blocks. In the roof truss area and above, reinforcing bars are inserted into vertical reinforcement channels in the corners of the mantle blocks and mortared according to manufacturer or structural specifications.
Chimney holders in the area of the roof truss, which connect the roof beams and casing stone with each other and also ensure a distance between the components, offer additional stability. They are considered lateral support of the shaft if a force-fit introduction into the supporting structure of the building is achieved.
Multiple occupancy: In the case of multiple occupancy of a chimney drown, several fireplaces in a house may be connected to the same flue pipe. The chimney system requires appropriate building authority approval.
Even if the builder only wants to operate a fireplace on a chimney flue, it can make sense in individual cases to choose a chimney system with approval for multiple occupancy in order to remain flexible for future developments in the house (additional storeys, changing apartment layout). The fireplace must also have an approval for multiple occupancy of the chimney.
From a technical point of view, single-coated chimneys are safer and more reliable, as there is no risk of escaping exhaust gases and their draught effect is stronger due to the smaller dimensions. See also Lexicon article ► Flue gas system, multiple occupancy
Matching the chimney to the fireplace or fuel: The properties of the chimney system must be matched to the respective fireplace chosen:
Outer shells (mantle stones): Mantle stones of system chimneys are in many cases made of poured concrete or lightweight concrete, but also of burnt masonry. A fire resistance period of the outer shell of 90 minutes is required if it is a solid fuel chimney.
Due to ever higher energy building standards, technical silicates with proof of usability, such as calcium silicate or fibersilicate, are increasingly being used for the production of the outer shell. In addition to excellent fire protection properties, these also have a high thermal insulation value.
The outer shells of the chimney systems are available in many geometric variants. As a rule, they are single or multi-stage, i.e. they include an additional draught for a solid fuel stove in addition to the draught for the central building and hot water heating. Depending on the system, further shafts are possible in the mantle stone for the supply air or for general pipe routing. Large manufacturers always offer their systems in a wide variety of variants. You can integrate several chimney systems within one outer shell.
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assembly or installation on site: Manufacturers often offer both variants:
Acceptance by the chimney sweep / chimney sweep: The local chimney sweep / chimney sweep plays a central role in the planning and execution of flue gas systems. After completion of the work and before commissioning, the system is inspected and approved in Germany by the chimney sweep/chimney sweep.
It makes sense to involve the chimney sweep/chimney sweep during planning and construction in order to avoid later problems during acceptance. In particular, the plant concept should be discussed with him before the start of the work. It can also be useful to inspect the construction during the execution.
Renovation of chimneys: Single-shell chimneys that were built up to the 80s are now renovation cases. Since the cross-sections are usually sufficiently dimensioned, it is possible to prepare the chimney for modern fireplaces with low flue gas temperatures by inserting a cross-section-reducing inner pipe with a condensate drain (insulated or uninsulated). If it is possible to place the combustion air supply in the remaining chimney cross-section around the inner pipe (air-exhaust system, LAS), the fireplace can also be operated independently of room air. Many regional companies explicitly offer chimney renovations, for which there are a variety of special products.
DIN EN 1443, Flue gas systems - General requirements
DIN EN 12446, Flue gas systems - Components - Outer shells made of concrete
DIN EN 13384-1, Flue gas systems - Heat and flow calculation methods - Part 1: Flue gas systems with a fireplace
DIN EN 13384-2, Flue gas systems - Heat and flow calculation methods - Part 2: Flue gas systems with several fireplaces
DIN EN 15287-1, Flue systems - Planning, installation and acceptance of flue gas systems - Part 1: Flue systems for room air-dependent fireplaces
DIN EN 15287-2, Flue systems - Planning, installation and acceptance of flue gas systems - Part 2: Flue systems for air-independent fireplaces
DIN V 18160-1, Flue Systems - Part 1: Planning and Execution
DIN V 18160-1 Supplement 1, Flue Systems — Part 1: Planning and Execution; National Supplement to the Application of Metal Flue Systems according to DIN EN 1856-1, of Inner Pipes and Connectors according to DIN EN 1856-2, the Permissibility of Materials and Corrosion Resistance Classes
DIN V 18160-1 Supplement 2, Flue Systems — Part 1: Planning and Execution; National supplement to the application of ceramic inner shells according to DIN EN 1457, assignment of the marking classes for mounting exhaust systems
DIN V 18160-1 Supplement 3, Flue gas systems - Part 1: Planning and execution; Supplement 3: National Supplement to the Application of System Flue Systems with Plastic Inner Pipes according to DIN EN 14471
DIN 18160-60, Flue Systems, Part 60: Evidence for the Fire Behaviour of Flue Gas Systems and Components of Flue Systems — Terms, Requirements and Tests
BImSchV, Federal Immission Control Ordinance
EnEV, Energy Saving Ordinance
►MFeuV, Model Combustion Ordinance
►Federal Association of Chimney Sweeps
Source: bauwion
