Saving heating costs - an interview with Michael Merscher
Maximum comfort and maximum energy savings with home ventilation
An interview with ventilation expert Michael Merscher, 1st Chairman of the Interessensgemeinschaft Dezentrale Wohnungslüftung e.V. (Interest Group for Decentralised Apartment Ventilation). (IGDWL)
Energy - always an expensive commodity - is reaching new record levels this year. According to a forecast by the non-profit consulting company co2online, consumers will notice the price increases especially when it comes to heating their homes. This is because heating, with a share of around 55 percent, is the biggest energy guzzler in the household. When considering possible savings on heating costs, it is worth taking a look at an increasingly popular home technology, the comfortable ventilation of living spaces. Michael Merscher, 1st Chairman of the IGDWL e.V. association, provides interesting insights into the high energy efficiency of this technology.
1 Why is it possible to use living space ventilation and do without window ventilation, which is particularly cost-intensive in winter?
In the case of living space ventilation with fan-assisted ventilation systems, intelligent electronics and sensors only ventilate as much as is necessary. If you ventilate via windows, you have to know exactly when it is the right time to open and close them. Otherwise you ventilate too little or too much. Often people ventilate "incorrectly": the window is set to "tilt" in the good faith of an air exchange and left open behind the curtain for a long time - often forgotten. In reality, however, almost no air is exchanged, only a lot of heat is lost, surfaces cool down and you can get moisture problems where there were none before. A home ventilation system with heat recovery extracts heat from the exhaust air during air exchange and returns it to the fresh air. In this way, even less energy is consumed than in systems without heat recovery. So if you want maximum comfort and maximum energy savings, a system with heat recovery is the optimal choice.
2. Are there further energy saving potentials with ventilation systems?
As already mentioned, the automatic control system only ventilates as much as necessary and, in the case of units with heat recovery, also recirculates the room heat. In addition, CO2, chemicals from furniture and furnishings, gases and odours are always quickly removed. It should also be remembered that people do not only perceive a certain temperature as comfortable, but that humidity also plays a decisive role. Because a demand-controlled system only ventilates as much as is actually necessary, the room humidity does not drop unnecessarily in winter. There are even systems that significantly influence the humidity in the room through so-called humidity recovery. In many cases, this can lower the room temperature without making it feel any different for the occupants. Just one degree difference can reduce heating costs by about 5-8 percent.
3. How exactly does heat recovery work?
This is a rather complex but easily explainable process in the so-called heat exchanger of a ventilation system. There are various methods and processes for extracting heat from the exhaust air. Typical designs are cross-flow or cross-counter-flow heat exchangers, rotors or regenerators, as well as heat exchangers, for example in heat pumps. By means of fans, "used" room air is conveyed outside and at the same time the same amount of fresh air is fed back into the room. The air flows through the heat exchanger on its way outside. In the process, it passes along a surface made of plastics, various metals, foils or ceramics. Now the first part of the heat transfer begins: The air releases part of the heat energy (i.e. the heating energy previously put in) to the heat exchanger. Depending on the operating principle, this energy is stored or directly transferred to the next step: fresh air, which is still cool, flows along the other side of the heat exchanger. Here, the previously absorbed energy is transferred to the cooler air. The air is thus heated by the heat exchanger without fresh air and extract air mixing. Or to put it quite simply: the heating energy is "extracted" from the exhaust air and transferred to the fresh air.
4. How much heating costs can be saved with modern living space ventilation?
That is very difficult to say. I don't want to give anyone false hope with slogans like "savings of up to 40 percent are possible". You have to look at each case individually, anything else would not be serious. For example, if someone ventilates rather little (or almost not at all), he will not have any savings after the installation of a living space ventilation system. And there are also people who still open the windows in spite of a living ventilation system in the house. Everyone should live exactly as they want to, i.e. if someone wants to hear the birds, the wind or the nocturnal hustle and bustle of the street café through an open window or simply feels the need to open the window, then so be it. But then the savings are smaller. If someone ventilates a lot, on the other hand, the savings effect with a ventilation system can be very large. In modern, well-insulated buildings, the effect is greatest. In most cases, the only way to get moisture out of the building and prevent mould problems is to ventilate the home. If an energy consultant or a system planner knows the exact parameters of a flat or house, he can calculate the possible savings quite accurately. These may well amount to a potential of up to 30 percent (or in individual cases even more) of the heating costs. Whether the user can exploit this potential, however, is a very individual question. But home ventilation is much more than just an energy-saving tool. We must not forget that it is also a question of permanently fresh air, health, comfort and much more when one decides to use a home ventilation system. It provides continuous ventilation when the windows are closed, so that mosquitoes no longer enter the home through open windows, allergy sufferers benefit from pollen filters in the systems and a potential burglar has a hard time because he will not find any tilted windows through which he can enter.
5. What about the electricity consumption of the ventilation units?
I already mentioned it briefly, the electricity consumption of a living space ventilation system is significantly lower than the possible savings potential. One can say that the savings are always at least as high as the electricity consumption of the home ventilation. So you don't "pay on top" for the operation of the system. For a 100 m² flat with a modern building standard and a state of the art flat ventilation system, the electricity consumption is roughly 15 to 20 W on average. Over the course of the year, this amounts to about 130 to 175 kWh.
LUNOS is a member of IGDWL e.V., the association of the community of interest in decentralised residential ventilation. This is part of the Good Air Initiative.
Michael Merscher is Technical Manager and member of the management of LUNOS. He is also the 1st Chairman of IGDWL e.V.