"It's about balance."

Martina Metzner
17. April 2019
Engineer Markus Pfeil and his office Pfeil & Koch ingenieurgesellschaft are specializing in integrated energy concepts. (photo: Fabian Stürtz | Photographer) 

In an interview, Professor Markus Pfeil advocates that resource-saving, efficient, and integrated energy and air-conditioning concepts should be given a greater emphasis in the practical work of architects. After the ISH trade fair, we talked to him about product highlights and the future of building services engineering.

Whether a breathing façade for the dm headquarters, a wooden passive house for German Federal Environmental Foundation (DBU) or an ice storage unit for FESTO: Is this research spirit also to be found among many of your BSE colleagues or are you rather the exception?

Markus Pfeil: I don't want to presume to judge the whole industry. For our office, I can say: yes, we have a spirit of research. Both my partner, Holger Koch, and I come from research. Many BSE offices tend to come from the utility engineering sector. We focus on an integral approach, which is also the subject of my teaching at the Münster School of Architecture. To begin with, we look at the building and the building envelope.

For the new office building of the German Federal Environmental Foundation (DBU) in Osnabrück, PKi, together with METARAUM Architekten, developed a building shell made of wood and hemp. (photo: Fabian Stürtz) 
Thanks to the resource-saving combination of envelope, groundwater cooling, combined heat and power unit, and photovoltaic system, the DBU building is a plus energy house. (scheme: PKi) 
Which BSE concepts will gain more importance in the next few years?

For one thing: For us, an integrated energy concept comprises ten components. In principle, each energy concept is developed individually. It's a question of balance: the building physics measures are important to reduce the technology. And bringing qualities in buildings to the fore that are useful for people. We don't construct buildings for the sake of saving energy, but for the sake of people.
For another thing: The future of energy supply on the electricity side will increasingly come from renewable sources. Photovoltaics will play a decisive role in building design. For architects, this means the integration of photovoltaics, that is the active building envelope as a power plant, in an architecture-compatible manner. In the future, electricity will become an even more important energy source that must be used very efficiently in buildings.

In addition to thermal insulation, the heat pump is also considered to be a kind of savior in terms of the energy turnaround. What do you think of that?

The heat pump has an enormously important role to play in this respect: it uses electricity to generate heat efficiently. However, the heat pump must be very well incorporated into a concept. The question where the heat comes from must be answered thoroughly – ideally, it is obtained as geothermal energy from a geothermal probe or a well.

The ice storage unit at FESTO (photo: SONDERWOMAN PHOTOGRAPHY) 
During the tour at ISH, you took us to 'Naturspeicher', a Swabian company that supplies ice storage systems. When is it worth thinking about an ice storage system?

First of all, you have to understand why an ice storage is a heat source: If I put a small bowl of water in my freezer compartment, then heat has to be extracted until ice forms. This process is equivalent to a heat supply – but at a very low temperature level. For example, in rural areas, where there is no district heating network and the geological conditions may not allow a well or a geothermal probe to be built, an ice reservoir in combination with a heat pump could be a good solution. We implemented this for the Festo office building with a 1,300 cubic meter ice storage unit. Naturspeicher offers a product for smaller scale applications, such as a single-family house. A combination of water, ice storage, regeneration by air, with a fan, and a small pond located above that acts as a short-term storage. A very clever approach.

At ISH we saw that many suppliers from the conventional heating sector are switching to fuel cell technology. They say that this is no competition to photovoltaics and only an interim solution. Why is that?

This is an interim solution in so far as the fuel cell, like the one from Solidpower, requires natural gas as an energy source. It produces hydrogen via a natural gas reformer, and only hydrogen is the fuel for the fuel cell. What distinguishes the "Blugen-BG 15" is an electricity efficiency of 55 %. This is enormous for decentralized power generation and at the level of current large-scale power plants. In the long term, we will have to move to a situation where fossil fuels are no longer used to produce electricity, heat, or cold.

For smaller households, you recommend pellet heating in combination with a photovoltaic system.

Yes, because pellets and photovoltaics are an excellent combination – they use so-called renewable energies and do not impede each other. We use photovoltaics to generate electricity, with pellets we generate heat. And a pellet boiler can also do well with a solar thermal system for water heating, especially in summer.

Generating electricity from pellets is not possible for the time being. This is where the "Pellematic" boiler from Ökofen comes in, which has a Stirling engine mounted on top. An ancient invention, very rarely seen, that manages to produce electricity from heat. Proportionally, it generates much less than the fuel cell – but biomass as an energy source makes this pellet boiler very interesting.

In the field of air-conditioning technology, you have presented two systems that improve ventilation in rooms. How does it work?

At Howatherm but also at LTG Air Tech Systems – two manufacturers for large-scale applications, Howatherm for halls and LTG for offices – we have seen the principle of 'transient' ventilation. Here, air does not flow into a room continuously and steady but in a pulsating manner. This alternation of switching on and off results in a very good indoor air mixture. At the same time, draughts are prevented – a major challenge when planning stationary ventilation systems.

At Kiefer, we saw a kind of hypocaust system – a hot-air heating system which was already used in Roman antiquity. Isn't that a niche theme?

Building component activation using water is standard, and where it is used, it can serve very well. Water is an exceptionally good energy source, while air principally isn't. Nevertheless, I think Kiefer's approach of integrating the system into the design is clever: if air is needed anyway, you can use it to cool or heat. This way you use the inertia of the building's mass. However, this modern form of hypocaust heating requires a very integral approach.

Ki has developed a "breathing" façade for the dm headquarters in cooperation with LRO Architekten. (photo: PKi) 
At the dm headquarters, fresh air is blown into the rooms in a pulsating manner and then extracted again. (scheme: PKi) 
Following the passive house concept, completely different energy-saving concepts are emerging today. Is the passive house outdated?

One has to consider the qualities of the passive house – it will not be possible to surpass them for a long time, because the highest level has been reached in terms of building physics. If the demands are very high, as is the case with energy plus houses, one would always want the envelope of the passive house. It provides very good thermal insulation, high air-tightness, and extremely energy-saving windows. In general, one must be grateful to the passive house movement that these products have arrived on the market at all.

Do you think that young people today are sufficiently aware of these topics and building services in general?

My experience is that architects see themselves primarily as designers and that the importance of energy issues is only gradually recognized. My job as a university teacher is to give students an overview so that they know what questions they need to ask and what possibilities they have. Many young architects are interested in this field, but social change is also necessary. Something is happening, as we can see from the Fridays for Future student protests. I hope the future students will ask: How can we change the world? How can we build outstanding energetic concepts? And at the same time achieve good design? 

Thank you very much for the interview!

Markus Pfeil (*1967) studied mechanical engineering and energy technology from 1987 to 1995. In 1997, together with Holger Koch, he founded the engineering firm Pfeil & Koch ingenieurgesellschaft based in Stuttgart and Cologne, which specializes in integrated energy concepts for buildings. Since 2011, Pfeil has been Professor for "Integrated Building Services Engineering" at the Münster School of Architecture of the Münster University of Applied Sciences.

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