In cooperation with the Technical University of Berlin, we prepared a 3-day study trip for a group of 24 experts from the Czech Republic visiting inspiring buildings with professional guides and an interpreter into Czech. The aim of this trip was to present 6 examples of current construction projects in Berlin, buildings with very low energy intensity and current technologies such as controlled mechanical ventilation, PV, gray water management systems, green façades and roofs. We monitored technical parameters and other information from the project preparation process, construction implementation and the actual operation of buildings meeting sustainability parameters. We were interested in these buildings not only in terms of energy operating demands but also the energy needed for the production, construction and demolition of the building (LCA).  Sustainable measures such as natural and recyclable building materials, water management, green façades and roofs, and the development of community renewable energies in cities were subject of lively discussions during the program. More information about the visited buildings can be downloaded HERE.

” People cannot live in greenhouses.”

” Sixty percent of harvested timber is burnt – it needs to be used in construction.”

“In Berlin, electricity may not be used to cool buildings.”

” We do not need any new buildings any more – we only need to optimize the old ones.”

These are some of the ideas we heard on a trip visiting low-energy buildings in Berlin.

Author’s article by journalist and architecture promoter Karolína Vránková

We could subscribe to some of the participants’ ideas and (passionately) argue with some others. For example, with architect Eik Roswag-Kling, who is the founder of the ZRS Architekten studio and also manages the Natural Building Lab at the Technical University of Berlin.

His objective is to return to “low-tech”, i.e. to reduce technical installations in the buildings – this also applies to ventilation systems and heat recovery. His visions are buildings made of natural materials, he prefers wood and clay plaster. This type of plaster can, to a certain extent, regulate the indoor environment, such as air humidity. “In such a building it suffices to air the rooms by opening the windows twice a day, and no ventilation systems will be needed,” explained architect Roswag-Klinge.

But does this not mean an increase in CO2 inside the building? Does not ventilation without heat recovery mean unnecessary energy losses? There was a long discussion about that at the Technical University without any clear result.

Nevertheless, all participants agree on most of the sustainable principles – they are guided by them in Berlin as well as in the Czech Republic: optimal orientation in relation to cardinal points, compact shape, quality insulation and windows, alternative energy resources such as waste heat or heat pumps, use of wood as a construction material even for multi – story buildings.

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We visited six buildings, each of which providing us with new experience.

NO. 1 FLEXIM, 2016

ZRS Architects

usable area 9,900 m2

The building located in the largest German housing estate Marzahn greeted us with a “Trabant” in the hall and the hall surprised us by its monumentality – a timber structure stretching over three floors, which is much more than the timber buildings we are used to seeing in the Czech Republic.

Our guide here was architect Andreas Pohl from ZRS Architekten.

It is actually a hybrid construction – the basement is made of reinforced concrete, the upper floors offer a combination of concrete and timber, the outer shell is a timber-framed civil structure. As this is a production building, it was necessary to oversize the civil structure in terms of its structural stability. According to the regulations, it was necessary to ensure a 90min fire rating and therefore the timber elements had to be oversized by 1/3 of the volume.

Waste heat is used for heating. The waste heat comes from a nearby wastewater treatment plant using a heat recovery system. The building is shaded by louvres and ventilation is provided in accordance with the “low tech” principles using windows only.

Flexim manufactures measuring instruments. It was established as a small garage company shortly after the fall of the Berlin Wall. The company has grown ever since and hopes to continue to grow. The head office is ready for that. Production and office workplaces are concentrated in three atrium buildings, three other equally large modules could be added to the land plot. Flexibility, use of timber, low energy consumption – all this is what the owners want to use to point out that their company is looking into a (sustainable) future.

NO. 2 SPREEFELD, 2014

carpaneto architekten, fatkoehl architekten, BARarchiteten

60 flats in three  block of flats

price 2,100 EUR m2 including land

Spreefeld is a housing estate, experimental in almost all respects.

It is fitted with shared common rooms and terraces, the residents maintain the spaces between houses, the houses are in passive standard, there are photovoltaic panels installed on the roof and it is not possible to get access by car here. So, in fact, nothing here looks or works the way we are used to from block of flats in the Czech Republic.

Silvia Carpaneto, one of the architects and also a resident in this estate, was our guide here.

Even the design of this non-standard estate did not proceed in a standard way. The promoters invited three architectural studios, which then developed the design together. They emphasized the function, rejected all the more luxurious design solutions, everything is made of standard elements. Three blocks of flats were built offering various types of spaces: standard flats, cluster flats, and the inhabitants share the kitchen and the living room. Furthermore, they include social spaces, commercial spaces and offices.

The flats are of co-operative ownership, each co-operator has made an investment – twenty percent of the flats are provided to people without the necessary funds. They acquired the land on the basis of their innovative project from the federal state of Berlin.

Technically, it is a hybrid construction: it combines concrete load-bearing elements with timber, the outer shell is a frame construction insulated using wood wool. The building is low energy. It is heated geothermally and by means of a common gas cogeneration unit. Solar panels supply the inhabitants with 30 percent of the electricity demand. Each flat has its own ventilation system with recuperation.

While most activities, including maintenance of greenery between the buildings, are performed by the residents themselves, the heating and ventilation systems are controlled by a professional. “It took two or three years to find an optimal set-up. We do not want to mess with it”, says Silvia Carpaneto.

NO. 3 WALDEN 48, 2020

Scharabi Architekten & Anne Raupach

usable area 4800 m2

price 11 million EUR

Walden 48 is a timber block of flats but it has a “city-like” façade made of gray slate facing Landsberger Allee street.

On the other side, the house faces cemetery greenery and has a wooden façade with loggias. However, we learn that the wooden façade is not allowed in Berlin – for fire safety reasons. Scharabi Architekten just tried it and it worked out. “We do a lot of things that are not allowed. We believe that it is necessary to try and then see that it is possible, “says architect Susanne Scharabi, who was our guide here.

The façade is not the only innovative element.

This building with 43 flats and 6 floors is probably the largest timber construction in Berlin. Everything is made of wood, including the elevator shafts and staircases. The only thing made of concrete are the staircase and fire-rated walls. The load-bearing wooden beams are glued from beech wood and, according to the architect, their load-bearing capacity is similar to concrete. The outer walls are of frame construction with wood wool insulation, interior partition walls are made of solid wood. It is heated by a geothermal pump with supplementary gas.

The building was constructed by the so-called “Baugruppe”, a group of individual families that jointly invested in the construction project.

Thus, the residents have known each other since the construction period and they use common areas on the ground floor and a shared roof terrace. The atmosphere is therefore homely and the wood along staircases and in the corridors emphasizes it.

NO. 4 STUDENT RESIDENCE BERLINOVO, 2017

Berlinovo Topteam

usable area 3747 m2

price 1,928 EUR/m2

The Berlinovo real estate agency focuses on cheap rental housing.

And this is the case of a 129 micro-apartments for students in the Lichtenberg district of Berlin. This place shows that timber is also a suitable material for such buildings. Timber enables inexpensive and fast construction – in this case, 9 months.

This six-storey building has been constructed as hybrid civil structure – the load-bearing elements are made of concrete, the partition walls and outer cladding are made of wood. In this case, a wooden façade was not permitted. The building is therefore plastered and the exterior plaster has a wood motif – above life-size.

NO. 5  HUMBOLDT UNIVERSITY – PHYSICAL INSTITUTE IN BERLIN, 2003

Augustin und Frank Architekten

usable area 9700 m2

The building was designed in the late 1990s, at a time when urban warming seemed insignificant and distant.

It is therefore a typical “greenhouse” – a concrete structure with a glass façade. As a rule, such buildings suffer from overheating and are dependent on intensive cooling. However, electricity-driven cooling systems are not allowed in Berlin. That is why rainwater cooling and the most low-tech system – climbing plants on the façade – come into play here.

The building is not connected to rainwater drainage but rainwater is retained in five tanks in the atrium and used for flushing and also for the so-called “adiabatic” cooling – it is injected into the air that enters the ventilation system and cools down through water evaporation. The water that does not fit into the tanks overflows into a pond in one of the atriums, and evaporation from it also improves the micro-climate in and around the building.

Rainwater is also used to irrigate the climbing plants that cover the façade in the atriums and on the southern side of the building.

The plants grow from the ground and also from containers installed on higher floors.

The costs of these plants are about ten times lower than the costs of louvre shading. The efficiency is higher – the plants do not get hot, on the contrary, the evaporated water cools down the microclimate. Of the ten tested plant species, wisteria (Wisteria sinensis), which is hardy and grows to a height of up to 40 meters, proved to be the best option. “The only disadvantage is that the plants cannot be controlled,” as our guide Marco Schmidt, who monitors the experimental system as part of the Berlin Senate project, told us with a pitch of salt. Although the climbing plants cannot be pulled out like louvres and sometimes it is a little dark inside, they can turn a hot greenhouse into a pretty pleasant place to live.

NO. 6 TIERPARK OFFICE BUILDING, 2019

ZRS Architekten Ingenieure

“According to forecasts, the population in Europe is not expected to increase until 2100. That is why we do not need any new buildings,” said architect Eike Roswag-Klinge from ZRS Architekten at the introductory presentation. In her view, it is necessary to optimize the existing ones at the moment. An example of this radical way of thinking is the reconstruction of a panel building from the 1970s in Tierpark, the zoo of the former East Berlin.

As Tierpark was in the East, the head office was located in a small panel building.

However, in the new millennium, the building became obsolete, with gaps between the panels in the winter and getting overheated in the summer. A decision was made to demolish it. ZRS Architekten came up with an alternative solution. They proposed replacing only the façade and windows and continue to use the rest of the building.

Concrete panels from the time of the GDR were thus replaced by timber ones, insulated using cellulose and fitted with insulating windows. The façade is made of larch wood, no one would recognize from the outside that this is a panel building. However, almost everything remained in its place inside, including floors, ceilings and built-in furniture. Energy consumption has been halved. In particular, CO2 and the so-called “grey energy” were saved thanks to the built-in materials.

The building is insulated and its cladding is sealed according to the latest parameters, only the windows are used for ventilation.

The last excursion during this trip thus sparkled a similar debate as during the introductory presentation. Can low-energy, highly sealed buildings be built without technologies? Can they do without recuperation and forced ventilation? Can they really be “low-tech”? The ultimate answer was not found this time, either. After all, all the other buildings we visited brought out a number of questions in addition to answers. It is clear that sustainability is a comprehensive concept and will be defined much more broadly in the future. This is not only about energy demand for heating or hot water. Built-in energy and CO2 will need to be assessed, too. It will also be about material flows and their reuse. It will be necessary to look at the entire construction system.

Nothing simple but the motivation is quite strong:

“According to the latest forecasts, the Earth may warm up by 1.5 degree as early as 2030. That is in 7 and a half years. What are we going to do by then? ”asks Eike Roswag-Klinge.

Thus is one of the questions we brought back with us from Berlin.