Flues used for wood fires are systems that naturally discharge the flue gases out of the house.
Exhaust systems are divided into two main groups based on the material used:
• Stone-like material;
• Metal systems.
In most cases, metal systems are used in the Netherlands, as this is usually cheaper and in addition, the risk of improper functioning is smaller with metal systems. The building regulations do not require a specific type of material for exhaust systems. However, the material should be fireproof (NEN 6062) and non-flammable (NEN6064). The fire safety (and other aspects such as leak protection, smudge resistance, etc.) are tested according to the NEN 6062 norm, also known as the TNO label. Furthermore, a KOMO-label can be provided to an exhaust system. This discharge material complies with the NEN 6062 standard, and also meets all the requirements of the building regulations and is absolutely safe. Since 2005, all systems must also be provided with a European CE label.
There are several exhaust systems available on the market:
1. Single-walled stainless steel systems, suitable as connection pipe from appliance to exhaust system or as renovation of an existing flue;
2. Double-walled insulated stainless steel systems, suitable as an individual, independent exhaust system;
3. Double-walled stone exhaust systems, suitable as an individual, independent exhaust system;
4. Stainless steel flexible pipelines (single or double walled) suitable for flue renovation;
5. Single-walled steel chimney, suitable as a connection pipe (in sight) from a wood stove to an exhaust system.
Focus areas for flues for wood burning appliances
Below are a number of points of interest that are important in the purchase and installation of a exhaust system suitable for wood stoves:
• Flue gases: The maximum fume temperatures are 600 ° Celsius, the average temperatures that occur during the combustion are around 400 ° Celsius;
• Material: Eliminated systems (therefore no longer accessible) are made of stainless steel grade 316L;
• Diameter: The connection size on a wood stove is also the flue diameter. With open fires, the dimensions of the fireplace, in combination with the applied chimney height determines the final flue diameter;
• Insulation: Double-walled systems are equipped with high-quality insulation, which optimizes the thermal draft and enables safe installation;
• Duct installation and outlet: To ensure proper operation of natural draft, the proper installation must be determined in advance. The outlet must be in the vicinity of the ridge, in the case of a gable roof. Any adjacent building (e.g. expansion) may adversely affect the natural draft of a exhaust system. The duct should also be installed as vertical as possible. Applying up to 2 turns of 45 degrees is allowed. The installation instructions provide the necessary information;
• Flue renovation: In general, it can be argued that the older existing masonry flues are not suitable for the connection of a stove or fireplace. These channels may show signs of leakage, or the construction is not suitable to withstand higher flue gas temperatures. This can cause damage to the flue and / or house. Our advice is to renovate the flue. This can be done by means of rigid stainless steel flue elements (with a straight chimney) or a flexible chimney lining (with a curved flue). Between the new lining and the existing flue, vermiculite insulation pellets are applied. These ensure that the lining maintains the right temperature during the burning;
• Installation: Ensure a fireproof installation. All systems must be equipped with a fireproof casing so the surrounding structure is protected against fire;
• Environmental nuisance: for the outlet at the roof, the smoke nuisance for the environment must be taken into account. In the NEN 2757 norm are requirements drafted, and the installation instructions from the supplier also provide directions in there;
• Maintenance: The cleaning and inspection of the exhaust system should take place 1-2 times a year. This to prevent any chimney fires. To avoid contamination of the exhaust system and of your environment, only burn dry and clean wood.