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The Energa - Barbas


Environment-friendly wood burners 

The Energa is a modern built-in fireplace provided with a patented filter of ceramic material with a finely-woven structure. The smoke gasses are transported before they leave the fireplace and the microscopic dust is combusted by the high temperatures. So the ceramic foam filter ensures a lower emission of organic microscopic dust. Due to the enormous heat reflection the ceramic filter also ensures a better combustion with higher efficiency as a result.


Due to the sponge-like structure the filter stops the flaming parts and prevents a chimney fire. Furthermore, the filter isolates very well as a result of which the temperature in the chimney will be lower and give off more heat to its environment with again a higher efficiency as a result.  



Ceramic filter

Classique avec une plaque pour les flammesFiltre en mousse de céramiqueFiltre en mousse de céramique

      1. With classic flame turning plate                 2. Our ceramic filter:  microscopic dust is cached in the filter and combusted.






Wood-burning heaters and fireplaces need a certain height in order to function well, while consumers rather have a lower model from the aesthetic point of view. Thanks to the ceramic filter we can build well functioning heaters which are much lower then the current ones’.


‘That is why you can not only distinguish yourself in quality but also in looks from other producers. An absolute surplus point in this market which is for the most part all about the design .’ Eric Smit explains, product development engineer at Interfocos.


Eric Smit

In an interview with Agentschap NL November 2012 Eric Smit, product development engineer at Interfocos, explains this innovation.

You can read the complete interview here below.



Interview with Agentschap NL (November 2012)Eric Smit, houtstook expert

At Interfocos they dont like to lack behind. On top of that, they rather be the first. therefore the company also spends time and money on innovating its operational management. For example in 2008 a brand-new lacquer installation was put into use. With this modern and environment-friendly lacquering line Interfocos is able to handle several orders at the same time and it is not necessary anymore to spray in series. The result: a lot of flexibility and less stock. Also now the new innovation provides for a better environment performance and more flexibility. And also this time Interfocos applied for subsidy under the program Milieu & Technology from Agentschap NL. Thanks to the subsidy we were able to hire the expertise of Procede, the engineer agency in Twente’, Smit explains. Their knowledge and expertise were the reason that we understand better now how the filter works. As a result the focus has become more clearer.’ The choice for a filter was quickly made though. For flaring-out the microscopic dust a foam ceramic filter is currently the most effective method. Converters are focused on for example only to reduce the carbon monoxide and other gaseous hydrocarbons in the smoke gasses and not on the microscopic dust. Many manufacturers are focused on improving the isolation and air supply of the combustion room in order to achieve a better combustion. Although a better combustion provides less root but you cant totally prevent it. An other disadvantage is that optimizing the combustion room results in a certain geometry which are extremely limiting the degrees of freedom of the measurements of the heater. And that while consumers attach great value to design.



A better combustion quality and limitation of inconvenience were the most important starting points in order to have a critical look at the performance of wood-burning fireplaces. We expect that the European regulation becomes more stricter in the future’, explains Eric Smit. ‘If you want to continue to take the lead then it is needed to anticipate on that already.’ Smit refers to the European directive Ecodesign. This directive sets requirements to the ecological design of energy related products. And that also includes wood-burning fireplaces. That the directive can have far reaching consequences, appears from the prohibition on light bulbs. Since 1 September 2009 frosted light bulbs and 100 Watt light bulbs are no longer allowed to bring into the market within the Member States of the European Union. With the ceramic foam filter it works both ways’,according to Smit. On one hand you limit the emission of organic microscopic dust and on the other hand the efficiency of your combustion is higher; air-treatment and saving energy in one.’ Under microscopic dust is meant; floating parts in the air which have a diameter which is smaller than 10 micrometers. These parts can be very diverse in shape. Both the size, the source and the chemical composition are very diverse. Natural microscopic dust is created from the ground and sea salt from evaporated seawater droplets. Unnatural microscopic dust is emission through traffic, the industry and through households and arises mostly through combustion of fossil fuels and through grinding materials. In households it are often the open fireplaces and wood-burning heaters which causes problems through the emission of microscopic dust. Bad for the image of the wood-burning heater, while a well stoked heater and healthy sense can prevent many of the complaints. Microscopic dust forces itself into the airways and causes in that way harm to your health. Health complaints as a result of microscopic dust expresses in premature death, emergency admissions for heart and airway disorders, airway complaints and functioning disorders.



Ceramic foam filters are indeed new in the world of wood-burning fireplaces, the material itself is available much longer. This kind of filters are mainly used in aluminium forges in order to flare-out slags from the meltage. The filter is obtained by impregnating a polymer with an open structure with a ceramic slurry. Thereupon the polymer is combusted in the oven, as a result of which a ceramic foam remains. It stays remarkable that Interfocos applies the material in its fireplaces. 'The idea to do something with ceramic, slumbers for a long time’. Smit explains. 'My predecessor Frans Sulilatu used to work at TNO, just like me. Part of our job was testing the wood-burning appliances. One of those appliances had a ceramic flame turning plate. During the testing Frans Sulilatu noticed the plate glowing up during the burning.’ With that observation the idea was born that small, not-burned parts which are taken by the hot flow of air precipitates on ceramic and combust there. Years later at Interfocos, when the question arose how the emission of microscopic dust could be decreased, the ceramic-idea came up again. 'And because you want to have a filter which is integrated in the  turning plate, we started to search for a porous ceramic material’, Smit explains. 'Not much long afterwards we discovered foam ceramic. This material has been developed in Israel in the 90s and is used a lot in aluminium forges. And the material appeared to meet our requirements.’ A nice example of looking beyond the borders of your own field of study. The nice thing about foam ceramic is that it is besides porous also heat-resistant. Pleasant incidental circumstance; foam ceramic costs only a fraction of the price you pay for metal foam.

The foam ceramic filter.   The foam ceramic filter.



During the combustion of wood, root parts are whirling up due to the heat and disappear through the chimney into the open air. Root consists for the large part of organic and thus flammable material. By using the ceramic filter these root parts are still combusted. As soon as the parts flare-out on the filter the ceramic material transfers its warmth to the root parts with the consequence that the root parts will be completely combusted into vapour and carbon dioxide. As a result the emission of microscopic dust decreases. The mineral parts which remain and which have mainly a diameter of less then 0.1 micrometer, are flushed out of the filter by means of the smoke gasses and blown out through the chimney into the open air. An important condition because you dont want your filter to silt up. In the first instance we started to experiment ourselves with the dimensions of the filter’, Smit explains. But the results were very diverse and we were not able to explain why at one time the filter did flare-out the dust and the other time it didn´t seem to work.’ Thanks to the subsidy from Agentschap NL Interfocos had the financial space to hire external expertise. ‘A golden chance ’, according to Smit. Thanks to the input of Procede we understand much better now what happens in the filter and thus also why our experiments showed different results.’ About the outcome of the result from Procede Smit doesn´t want to say too much. If we do, we immediately lose our lead on our competitors, but I do have a tip for other companies: call in science in an early stage. Sometimes it appears that your intuition is not good, then you can choose to stick to that, but it is better to call in an expert for your problem and with grounded theories you can take a different road.’



To continue innovating is a must for Interfocos. But it always is a matter of balancing. Innovating is important, in that you you remain in the lead’, according to Smit. But it also must stay profitable. The idea of a ceramic filter appeared to be much more complicated then we thought at first instance. Fortunately we didn´t give up and are now able to produce lower appliances then the competitor. A big wish from the consumer has been fulfilled.’ And that consumer causes a lot of thinking. There are not only the esthetical wishes, in general consumers are also laymen. A well stoked fireplace or heater causes less inconvenience and emits much less microscopic dust’, knows Smit. It is just that not everyone has a command of this skill. With the design we are taking extreme circumstances into account and are trying to limit the possible negative influences of the user on the performance of the heater as much as possible.’ A bad stoked fireplace produces much more microscopic dust. This also means that the filter runs full much quicker and that the draught becomes less. While you want to have a self-cleaning filter. The choice of the pores size in the filter are therefore crucial. Besides the filter must be that robust so it doesn´t break,  for example if a woodblock accidently knocks into it. A filter should also not be too expensive, because then the purchase value of the heater becomes too high. In short, before a new heater is introduced into the market, many considerations and decisions have been taken in advance. As an engineer you rather have the best technique, but unfortunately you can´t avoid concessions.’



Durable warmth

Many people are not aware of it but wood-burning fireplaces provide for permanent warmth. Wood is after all a bio-based and thus a renewable base material. The market for wood-burning fireplaces and heaters is thus still increasing. In the Netherlands this is still a modest growth but in countries around us there is talk of a large increase of the market share visible. There is a clear trend in which the wood-burning heater more and more takes over the central heating and is considered as an important source of heat.

More and more people want to be independent when it comes to energy and warmth. And not only solar panels but especially also wood-burning heaters contribute to that. Maybe it sounds contradictory but more and more wood-burning heaters are provided with a plug’, knows Smit. And that offers possibilities again for the choice of the filter. One of the problems is that the filter must become warm before it can do its job. If you have electricity in the heater then you are able to preheat the filter. Ideal.’ Besides Interfocos builds in a relapse option for those moments that the electricity drops out while you are just so happy with your own, independent warmth supply.



Meanwhile the first models with ceramic foam filter are available on the market. Interfocos delivers them under the name Barbas Energa into the market. ‘This type is already in the List of Agentschap NL’, tells Smit enthusiastically. With that it is the only wood burner in the Netherlands that qualifies for MIA/Vamil.’ 

This doesn't mean that Interfocos rests on its laurels. Besides the ceramic foam filter the company investigates whether there are also other filters and materials available which deliver the same or better performance. At this moment we investigate the possibilities of new types metal filters’,Smit gives away a little. The results are stunning but there are also still quite a few hurdles ahead.’The emission of microscopic dust may not contain more than 40 mg/m3. Measurements with a similar filter show an emission of not more than 5 mg/m3. Far below the legal requirement. A very promising development. As mentioned before, the first results are great but that isn´t enough’, Smit assuages. But it has appeared from this project that the emission of microscopic dust can be decreased enormously.’ And that´s good news for the environment and the public health. 


More about the Energa-70-55

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More about the Energa 80-50


Barbas Bellfires 

P.O. BOX 6940 
Kidderminster DY11 9EW 
United Kingdom   


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