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Recirculating air or kitchen exhaust air (ducting)? The advantages and disadvantages of the extractor systems

In many ways, cooktop extractors cannot be compared to the conventional rangehood however, there is still one aspect that both types of appliance have in common. Both cooktop extractors and rangehoods can work with either recirculating air or kitchen exhaust air (ducting). With both operating modes, the cooking and roasting vapours are suctioned away by the extractor and odours and grease particles are removed safely. However, there is a difference in how the air is channelled: with recirculating air, the air that is suctioned away is filtered through a high-quality activated charcoal filter (cleaning and removing odour molecules) and channelled back into the room. In the exhaust air version, it is carried away to the outside. Which version is best depends on a number of factors – including the surrounding architecture. A comparison of the advantages and disadvantages of each system will help you make your decision.

Kitchen exhaust air and recirculating air – the different operating modes in a nutshell

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Kitchen exhaust air

As the name already suggests, the air that is drawn in, is then transported outside by an exhaust air extractor. To do this, the extractor will be linked to an exhaust duct system with wall sleeves. The duct system leads through an opening in the building shell to the outside. The opening does not have to be in an external kitchen wall, but can also be in the roof or cellar. Firstly, the extractor draws the steam directly away from the pot or pan and guides it through a grease filter, this cleans the oily particles from the air, and into a duct system. Thanks to the great design freedom of the BORA duct system (BORA Ecotube), plans can be created for longer distances, with no negative effect on performance. This enables air to be channelled to either the left or right, giving ultimate freedom for planning. The cooking vapours/ steam which are filled with odours are guided outside, through a wall sleeve in the exterior wall of the building. The backflow traps in the exhaust air duct prevent air from outside re-entering the building. It depends on where the system is installed, as special exhaust air accessories are used – from external wall fans to tiled roof fans to flat roof fans.

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Recirculating air

However, in a recirculating air system, the air remains inside the room. The extractor draws away the air that is filled with cooking odours and grease molecules, It is then filtered and returned into the kitchen as fresh, clean air. In addition to the grease filter, an activated charcoal filter is also necessary.
Once, the grease and food particles are removed by the grease filter, the activated charcoal then absorbs the remaining food odours from the air. The recirculating air system blocks any odour particles re-entering the room. When used over a long period of time, the extremely large filter surface of the activated charcoal gradually absorbs less and less odour molecules, until none are absorbed at all. For this reason, the recirculation filter must be changed regularly. Please see the service life or operating hours in the operating instructions of your cooktop extractor system. Depending on the system, the BORA recirculation filters have different service lives of between 1 and 2 years. This means that they work for a comparatively long time before a filter change is necessary.
Compared to kitchen exhaust air solutions, recirculating air solutions are considerably easier to install. For this reason, recirculation is generally preferred for smaller apartments, kitchens and refurbished properties. 

BORA Classic 2.0 System

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Which operating mode should you choose? Kitchen exhaust air (ducting) vs. recirculating air

Due to its basic operating principles every extractor system has different advantages and so suits every kitchen differently. A comparison of the most important features of both operating modes will help you to make a decision.

 

Exhaust rangehoods and cooktop extractors guide the moisture generated during cooking out of the room along with the exhaust air. In the case of extractors with recirculating air this is not the case. The latter does remove grease and odours just as the exhaust air system does, but it does not remove steam. For this reason, when using an extractor with recirculating air it is generally important that an adequate exchange of air is guaranteed – either through an open window or automatically using a controlled ventilation system. As with kitchen exhaust air system, it is important that sufficient fresh air can flow into the house.

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Assembly

A kitchen exhaust air solution cannot always be installed. If the building is new, find out beforehand whether or not it is possible. Due to the pipework needed and the opening in the wall to the outside, the installation of a kitchen exhaust air system is more costly and time consuming than that of a cooktop extractor in recirculating air mode. Particularly in rented flats, installation of a kitchen exhaust air system is more complicated than that of a recirculating air system. As a tenant, as well as information from the planner, you will need to obtain the landlord’s permission to install the extractor components. At the end of the day, the building must be modified and this must be approved by the owner of the house or flat.

 

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Energy efficiency

In winter, with an exhaust air extractor, along with the cooking vapours warm heating air is also channelled outside the building. The result: valuable energy is lost. For this reason, building experts recommend installing recirculating air systems rather than kitchen exhaust air systems with conventional extractor hoods in highly insulated new builds. In many new builds kitchen exhaust air systems are even prohibited. Contrary to conventional extractor hoods BORA systems work with a relatively low displacement volume, whereby from the outset very little warm air from the room escapes to the outside, however, in airtight buildings recirculating air is often the best option as such buildings generally have controlled ventilation systems. This automatic ventilation allowing the air to enter and exit the room ensures that moisture is safely carried away and, together with a recirculating air extractor, the air in the kitchen remains fresh. However, in older buildings, kitchen exhaust air is normally recommended. This is because there are often large temperature differences in old buildings, which encourage the formation of condensation. With a kitchen exhaust air system, the moisture in the air is quickly removed to the outside.

 

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Maintenance

To effectively remove odours, when using a recirculating air system, in addition to the grease filter an activated charcoal filter or special recirculating air filter is installed. Keep in mind that used over a long period of time, the extremely large filter surface of the activated charcoal gradually absorbs less and less odour molecules, until none are absorbed at all. For this reason, the recirculation filter must be changed regularly. This enables the extractor to continue providing fresh air. Please see the service life or operating hours in the operating instructions of your cooktop extractor system.

 

Kitchen exhaust air vs. recirculating air – the advantages and disadvantages of the systems at a glance

Recirculating air

Advantages:

  • Easy and inexpensive to install 
  • Can be installed in any kitchen, even in passive and low-energy homes
  • Design freedom (e.g. kitchen island can be freestanding)

Disadvantages:

Kitchen exhaust air

Advantages:

  • Low maintenance as no filter change is necessary 
  • Moisture in the air is transported to the outside with the exhaust air

Disadvantages:

  • In winter, energy is lost as some warm air is suctioned away and transported outside.

Your BORA partner will advise you on optimum planning options

Your BORA partner will advise you on optimum planning options

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