Building for Plants

Online-Interview: Wolfgang Fiel, March 31 2020
14 min to read

Topic: Domesticated Nature

We met with Thomas Auer, Managing Director of Transsolar Energietechnik, to discuss the “Expo Greenhouse” in Shanghai, for which he developed the energy and climatic concept and which is currently under construction. On top of this, we also took the opportunity to chat with the Professor of Building Technology and Climate Responsive Design at the Technical University of Munich about the current and future challenges in his sector in this age of global warming and to reflect upon the power of simulation as a design and communication tool, the looming paradigm change in research into thermal comfort, the role of the user and the intercultural added value of his academy, before returning to his greenhouse and to some musings about the unusual problems connected with building for plants.

Wolfgang Fiel: Dear Mr Auer. First of all, I'd like to thank you warmly for your readiness to take part in this conversation and I'll begin if I may with a question about your work. Although I don't know if you were involved in the founding of Transsolar, you're now the Managing Director of the company, which has offices in a number of locations. Could you please say a few words about the development of Transsolar?

Thomas Auer: Okay, starting perhaps with the basics: Transsolar develops energy and climatic concepts for buildings and also for urban quarters and districts with the help of simulation tools. The idea out of which we emerged in the mid-1990s was that of integrated design. In architecture, design is understood as the creative process of synthesising a range of different expertise. In fact, architects are always trying to synthesise influences from various directions into something that is more valuable as a whole. This is exactly the spirit with which we seek to participate in this iterative process by using productive simulation tools. Unlike many others, however, we use these simulation tools not as a means of expert evaluation but iteratively, to support the design process. In English, this is very elegantly described by the term “Informed Design”. Hence, we use information with the aim of – ideally – creatively stimulating the synthesising process. And this has much to do with personal chemistry. It works better with some and less well with others. This, I believe, is simply in the nature of things.

We've been doing this since the mid-1990s. I wasn't a founder of Transsolar myself but, rather, the first trainee (laughs). I did my traineeship with Transsolar in '93, started as an engineer in '94, became a partner in 2000 and have now also been Managing Director for several years.

Incidentally, Transsolar is a rather small office with almost 60 engineers in four locations. We've realised that a certain proximity to the client is extremely helpful to our way of working, even if the current crisis has shown us that certain things can also be very well resolved “remotely”. Maybe we'll reflect on this so much that we persuade ourselves to reduce in size back down to one office (laughs).

Expo Cultural Park Greenhouse Garden, Shanghai/China, design development, Delugan Meissl Associated Architects

Our philosophy, on the other hand, is that we want to understand not the system but the physics behind it.

F: I'm interested in the development of the office, in the question of whether your spectrum of activity and the related approach and tools have changed in the nearly 30 years since it was established. In other words: How much have issues such as climate change impacted upon your search for new or alternative solutions? I have the impression that, in this respect, you can definitely be counted amongst the “early adopters”.

A: (Laughs) In this case we can indeed claim to have been “early adopters”, even if the work itself hasn't changed so much. The tools, on the other hand, have certainly changed and enable us to produce many more results much more quickly today than before. But this also leads to a tendency to reflect much less today or, putting it another way, to simply try things out instead. It's possible that, earlier, we developed things rather more specifically in a certain direction and thought about them more before doing so. What generally happens today is that we interpret the results of all the simulations that we carry out and then often realise that, with a little reflection, we could actually have arrived at the same conclusions ourselves (laughs).

Now we produce a lot more data, which has both advantages and disadvantages. One common disadvantage is that all these data have to be interpreted. One example of an advantage is the fact that we now have the data that show that our gut feeling was right in the first place.

F: In the case of these simulations, surely the key issue is the ability to communicate the whole thing: Isn't it fair to assume that the results of a simulation can be communicated with more credibility than an engineer's gut feeling?

A: Yes, of course that's what it's about. It has a lot to do with communication. In truth, communication is our principal activity. Whereby, of course there are also frequently architects who say that we could avoid all this “simulation nonsense” if we would just tell them how things should be built (laughs).

F: I call that trust!

A: Then I always say: You wouldn't trust a structural engineer who wasn't able to calculate their structural solution. And we can't build something that we can't calculate. This means, of course, that we must be in a position to provide this proof. There's too much money involved to rely on experiments or speculation.

The Arid Desert Pavilion, 3D-renderings

What do plants actually need, what is comfortable for them?

F: In this connection I'd be interested to know to what extent there are historical models in your specialist field from which you can learn and that can help you to solve current constructional challenges. I ask this question against the background of an ecological park in Shanghai, on which you're currently working together with DMAA. Given that the greenhouse is a contemporary interpretation of a historical building type there are perhaps certain reference points upon which you can draw. I'm principally wondering about this with respect to the definition of the interior climate, which, in the case of plants, probably permits a certain variation that, potentially, could be linked with a reduction in the technical complexity. To what extent is your work related to people's expectations of being able to control something that is, in reality, uncontrollable?

A: As it happens, you're touching on the most interesting aspect. Even if I leave out a couple of steps here, the basic fact is that the philosophy of the building services engineer is that the temperature of a space should always be under control. Our philosophy, on the other hand, is that we want to understand not the system but the physics behind it. The physics that leads to the fact that certain conditions arise and that the architecture, the space, controls itself, while permitting fluctuations to occur. These fluctuations are a fundamental idea. We only implement technical systems in order to avoid certain peaks.

This can best be described in terms of the simple activation of constructional components or thermal building mass. We open the windows at night so that the thermal mass cools down and we can then use simulations to show the extent to which we are able to limit the temperature on the following day. But this whole use of thermal mass naturally only makes sense if I also permit fluctuations. This means, if the window is open at night the space will be colder. This enables the concrete slab to cool down so that it can absorb heat again the next day. But it can only absorb this heat if the temperature of the space rises. So the question is: What rise in temperature are we prepared to tolerate? In order to answer this, researchers have been investigating for years whether these constant temperatures are really a good thing. Indeed, I only truly feel pleasantly warm when I come in out of the cold. In other words, we believe that changing conditions have a positive effect on people. Naturally, the same applies to light. A diffuse level of 500 Lux might be good for reading or working on the computer but it's not necessarily also healthy. We're becoming increasingly aware of the fact that the body also needs periods of 1,000 or 2,000 Lux or even direct sunshine in order to maintain its vitamin and hormonal balance. That's why it's been common for some time to think in terms of daily doses of light, of the amount of light that we need throughout an entire day rather than at any specific moment.

And now we're attempting to rethink the idea of thermal comfort in a similar way.

F: Okay, but if I may butt in here am I not right in saying that this is a recent development? How long have researchers been addressing these subjects, surely for a number of years?

A: Yes, exactly. UC Berkeley has led the way in this area so far. We've known about these adaptive comfort standards, as we call them, for some time. In the early “noughties” it was noted that people in naturally ventilated spaces not only accept different conditions but also have a different definition of comfortable conditions than people in air-conditioned spaces. And the research in this area is now so advanced that this finding has been integrated into the norms. Dynamic conditions – conditions that change in terms of both time and position and, hence, have a positive impact on people – are the subject of the latest research, which hasn't yet reached the point at which it can also be integrated into the norms.

F: To what extent does user behaviour play a role here? When you use the word dynamic my first reaction is to think about user behaviour and about the question of how we can do justice to the unpredictable and highly dynamic movement patterns that users introduce into a situation. Can such parameters already be incorporated into the control of an interior climate or is this still a pipe dream?

A: Quite by chance, we've just made an application for a research project in which we want to do exactly this, to investigate movement patterns in an office building. Users wear a small transmitter that enables us to record their movements. One philosophy is that a range of conditions are created in one location during the course of a day, while the objective of the other is to provide a spectrum of varying conditions in different locations and to allow users to choose the place in which they feel comfortable. We want to investigate both these concepts within a test environment.

The Natural Rainforest Pavilion, 3D-Rendering

F: If I may return to the greenhouse, the particular challenge is probably the need to establish the best possible climate for the well-being of the plants. Which approach to determining the interior climate are you using in this project?

A: Yes, as you've just suggested the interesting aspect in the case of the greenhouse is finding out exactly which climate is comfortable for the plants. In the case of people we already know – or at least we think that we know – what makes them feel comfortable. But when we began to discuss the climate of the greenhouse we were somewhat surprised to discover that we still don't know much about what plants actually need.

F: Really!

A: Yes.

F: Assuming that you've discussed this issue with botanists, biochemists and other experts; does this mean that even they only partly know what – to take an example – a palm tree really needs in order to “live well”?

A: Yes. There is, for example, much debate about the subject of UV radiation. As botanical laypersons we naturally assume that plants need this. But the fact is that, for safety reasons, overhead glazing requires an extra film that generally filters out such radiation, as a result of which we can effectively no longer get sunburnt behind glass. To date, no one has been able to tell us whether this drastic reduction in UV radiation is a problem or not.

F: Okay. Here I'd like to relate this back to my question about historical models, of which there are undoubtedly many in the case of the greenhouse, given that it is an archetype of European architecture. Is the question of how orangeries or palm houses developed across the centuries at all relevant for you? At least this could provide a certain amount of empirical know-how about the suitable interior climate for plants.

A: Yes, of course we look at that, even if these old greenhouses and orangeries had single glazing rather than any sort of laminated safety glass. Due to the relatively small panes, the issue of overhead glazing was relatively unproblematic. This means that the interior of a modern greenhouse has a completely different radiation spectrum. In the case of DMAA's project in Shanghai, the plan was for the interior to have a desert climate. Hence, we looked at the climatic data for a range of deserts and, in doing so, our first discovery was that there's more than just one type of desert (laughs). In terms of climate, the greatest challenge is to create dry heat. But there's also the Gobi Desert, where it's generally dry but cold. Nevertheless, given the very high humidity in Shanghai in summer, we have to massively reduce the level of humidity in the air. However, when we asked the botanist how often we had to do this the answer was: “well, cacti love humidity and really flourish.” Thereupon we fundamentally questioned the need for dehumidification, especially in the light of the huge investment costs that this involves.

If temperatures in the greenhouse reach a very high level in summer, we must, for example, remove this heat by opening the windows. But then humid air flows in and if we don't want this humidity it has to be removed by the air conditioning. Re-cooling such a greenhouse requires huge amounts of cooling energy and, hence, a huge air conditioning system. But if we accept that the botanist is right, this leads to a completely different design approach and, hence, a completely different system.

F: Did you arrive at a decision here?

A: Yes, our current assumption is that we don't need any dehumidification.

And as the roof of the greenhouse wasn't big enough we proposed the installation of underwater photovoltaics.

F: I'd like to return to the historical predecessor with small panes of simple glazing. Is it really out of the question to repeat this approach and, at the same time, combine this with a contemporary architectural expression?

A: That's a good question that I wouldn't even dare to answer right now. Even in the case of small panes there'd still be certain safety requirements for overhead glazing. I can't say offhand whether we’d be allowed to build the greenhouse in such a way.

The client in Shanghai originally wanted to create an air-conditioned building, which was only possible with double glazing. But the huge disadvantage of double glazing is that it removes even more radiation, which must then be offset with artificial light.

F: The filter effect really reduces the total daily dose of light to below the amount required by the plants?

A: Yes, that's the case. The plants in this greenhouse generally grow in climatic zones that have much more light than Shanghai. This means that there's already a certain lack of daylight that has to be offset with the help of artificial light.

In addition to this, we were also able to show that the relatively high average annual temperature in Shanghai means that the savings resulting from the insulating properties of double glazing are much lower than the cost of artificially illuminating the plants.

F: And this enabled you to persuade the client not to use double glazing?

A: Yes.

F: So it's really about finding a proof that scientifically underpins a gut feeling. About using a simulation to show that this is really the case!

A: Precisely!

F: When you consider the overall ecological footprint of such a building the technological complexity of meeting certain standards clearly plays a significant role. Doesn't this lead you to consider making concessions in the area of spatial comfort in order to reduce this technical complexity?

A: No. You asked me earlier what has changed in our planning role and our everyday work. One thing that's really changed in recent years is the seriousness of this debate. And certain economic relationships have also changed. Photovoltaic energy has become really cheap. We've reached the point at which we can say that a building without photovoltaic energy represents a failure of design. And this insight is already shared by investors and project developers who are concerned that their properties will become a problem in ten years' time.

In the case of the project in Shanghai, for example, Roman (Delugan, editor's note) pushed these energy questions really strongly with the demand: “If we build a greenhouse it must be a zero-energy greenhouse, we need photovoltaic energy!“

F: This means that a PV plant was part of the strategy for meeting this zero-energy target from day one!

A: Yes, and as the roof of the greenhouse wasn't big enough we proposed the installation of underwater photovoltaics.

Restaurant Area, 3D-Rendering

The dialogue with DMAA is extremely open and very productive. With DMAA there's a search for ways of stimulating the architecture, of making it stronger.

F: From the climatic point of view is there really an ideal architectural form for a greenhouse or are the influencing factors too complex to enable the form to be reduced to the lowest common denominator?

A: The situation's really too complex to enable me to give a generalised answer. I believe that the ideal form of a greenhouse is more a function of the structure. How can I build an attractive structure using the minimum amount of steel? The fact is that the question of light, of solar gain, is central to a greenhouse. This solar gain depends upon the surface through which the radiation passes as it enters the greenhouse. Whether the building is a dome or a “shoebox” does little to change the relevant area. But I could also imagine that a combination of different plants that require both a lot of and little light could enable a completely different form to emerge.

F: Is the dialogue that you have with DMAA about such questions really iterative. Can you describe this process to us?

A: Okay, the first thing I should say is that the dialogue with DMAA is extremely open and very productive. There are a lot of architects who, if anything, find our input disruptive because they have a fixed design idea and merely hope that the engineers will destroy as little of it as possible (laugh). With DMAA there's a search for ways of stimulating the architecture, of making it stronger. In the case of Shanghai we only came together after the competition, so the form had naturally already been developed. But we're currently working on a competition in Vienna where we're also involved in the discussion of the form. Not that we only ever discuss the overall form – there are lots of other subjects. And, as I've already said, this is a highly iterative process.

F: This means that, in an ideal world, your cooperation with the architects begins during the competition, during the development of the project!

A: Yes.

F: Given that you're also a professor at the Technical University of Munich, I have to ask about the extent to which a synthesising planning process could be integrated into the curriculum of future architects. How do you at the university manage to get across the message that, in the future, the importance of the interface with the other professions will increase hugely?

A: Yes, that's a really good question. Well, at the Technical University of Munich we have Integrated Design. Here, architecture students in the third semester have to design something modest, such as a house, which they then develop together with the department of structural design. My opinion is that the engineering input for such a house can easily be provided by the colleagues from the architectural department.

We recently launched a discussion with students from the sixth and seventh semesters about introducing a BIM project, in which the model is then parametrically optimised in cooperation with specialists from the areas of climatic and structural engineering. Maybe such an approach has the potential to introduce more interdisciplinary and integrated design.

F: Now I must take a step back again. As you've spoken of BIM I'd be interested to know if you carry out the simulations that you mentioned at the start of this conversation with tools that you've fully or partly developed yourself or if there are suitable applications on the market.

F: A bit of both. The most important tool that we use for thermal simulations is known as TRNSYS and we're involved in its development. We do this through a small development team and also distribute it amongst a community of a couple of hundred users across the German-speaking region. If you're involved in the development you can naturally better meet your own needs.

The Cloud Garden, 3D-Rendering

The fact that we constantly have six young people from various countries in our Stuttgart office has done much to promote our intercultural nature.

F: A final question. How do you see the future development of Transsolar? Do you aim to grow further or do you constantly, so to say, align your development with the next project?

A: For us, turnover and growth were never qualitative criteria. And yet a certain level of growth definitely helps. Small offices always have the problem that they might be able to attract good people but they aren't able to offer them much in the way of promotion prospects. And that's where growth comes in.

Because growth leads to groups, and groups need leaders, and so it goes on. At the moment we're discussing how a generational change can occur without either abandoning the current philosophy or losing know-how.

F: That brings me back to the question of the multiple locations which – I assume – already contribute to the fact that intercultural exchange takes place within the organisation. What role does this play for you?

A: It plays a major role. One thing that's enabled us to come a long way in this respect is our in-house academy. Every year, we offer training scholarships in our office to six people from the so-called “developing world,” who have completed their training as an architect or engineer. We rent an apartment for these people and also pay them the minimum wage so that they can live well in Germany and spend a year learning with us. The fact that we constantly have six young people from various countries in our Stuttgart office has done much to promote our intercultural nature. For example, every large meeting in our office takes place in English.

F: How can one apply?

A: We announce it on our website. In the meantime it's become so well-known that we receive between fifty and a hundred applications.

F: The choice can't exactly be easy.

A: Yes, of course, but it's not always about finding the best ones. The six have to spend a year living together so they also have to fit well together as a team.

F: I think that that's an inspiring conclusion to this informative and open conversation, for which I'd also like to thank you warmly on behalf of DMAA!

A: Mr Fiel, it was my pleasure!

3D-renderings: ©DMAA
Coverphoto: © lily –

Photo: Silicya Roth


THOMAS AUER is the managing director of Transsolar and Professor for Building Technology and Climate Responsive Design at the Technical University of Munich since 2014. After its inception nearly 30 years ago, currently Transsolar employs about 60 engineers in 4 offices in Europe and North America. Deploying sophisticated design tools and strategies for climate responsive and energy efficient building design, the company has gained international experience working on a wide range of projects and a variety of topics, such as user comfort, building technology and passive design strategies, as well as strategies for districts and cities.

THE ACADEMY offers a one-year fellowship in climate-responsive building design for 6 young architects or engineers in the Transsolar office in Stuttgart. The fellowship covers tuition, travel and accommodation. The program provides lectures, tutorials and project work. The comprehensive and practical training combines theoretical background with hands-on experience: working on a personal project and on projects in the company. The goal is that the fellows will discover the opportunities of 'KlimaEngineering' in their home countries, where great changes are expected to take place in the near future.