Nieuwbouw Drees & Sommer hoofdkantoor brengt duurzaamheid in de praktijk

© Drees & Sommer/Maximilian Schwarz
© Drees & Sommer/Maximilian Schwarz
© Drees & Sommer/Maximilian Schwarz
© Drees & Sommer/Maximilian Schwarz
© Drees & Sommer/Maximilian Schwarz
© Drees & Sommer/Maximilian Schwarz

Dit artikel van journalist Lucas Ligtenberg verscheen in het internationale magazine PropertyEU

Straight from the drawing board: a prefab office lab

What will the office look like post-Covid, and how can its environmental impact be minimised? Drees & Sommer explores the possibilities at its new Stuttgart HQ.

Obere Waldplätze, where the new headquarters of consulting, planning and project management company Drees & Sommer (D&S) is located, is an unremarkable street in the suburbs of Stuttgart. In fact, at first sight, the 7,500 m² building, dubbed OWP12 after its address, does not really stand out amidst the other, fairly low structures. All form part of a Drees & Sommer campus that is not quite a campus yet. The company owns nine separate buildings on the same street and the plan is to transform the whole site into a park, including a still-to-be-built underground parking garage. ‘To build your own building is more difficult than somebody else’s,’ says Drees & Sommer’s CEO Steffen Szeidl during a tour of the new complex. ‘I have about four thousand colleagues here who have ideas for even better buildings.’ Since D&S is in the business of designing and developing ‘better’ buildings, that should not come as a surprise. The company refers to its new office headquarters, which opened last December, as its business card, a showcase of what it has to offer potential clients. As such, it is both a lighthouse project and test facility. Says a proud Szeidl: ‘We are designing and developing the building, and we own it.’

Function over aesthetics
OWP12 measures 70 x 20 x 20 metres and is neither shiny nor glassy, like a lot of new buildings. It may not be beautiful, but it is very functional. The philosophy behind it, which Drees & Sommer applies to all its buildings, is that the real estate sector has a special responsibility towards the planet and in combatting climate change. ‘In terms of CO₂-emissions, buildings are responsible for 36% of them,’ Szeidl points out. ‘By comparison: cars account for only 11%.’ It was one of the reasons why, four years ago, Drees & Sommer set out to design its own new main office as a zero emissions building which would preferably give energy back to the grid. At the time, the building was scheduled to be finished by mid-2021, but there was some delay due to Covid. ‘We did well, considering the pandemic,’ says Szeidl. The costs of the project amounted to €22 mln and D&S was able to finance this on its own. It applied for a subsidy for just one small application in the parking garage, a ‘smart’ solution for organising the charging of electric vehicles. Comments Szeidl: ‘You won’t believe it, but that is now the last part of our headquarters still not finished.’

Steffen Szeidl, CEO and a Member of the Executive Board at Drees & Sommer, gives a tour of the building, unpacking the elements and building process that resulted in this super sustainable, circular, net energy plus, modular and smart office building - a modern workplace ready for the future.

Spin-off effects
Drees & Sommer has annual turnover of approximately €500 mln and its R&D budget is about €20 mln per year. Of course, the new building is not for sale. Says Szeidl: ‘We won’t be selling this. We want to use the knowledge of developing this building in our business. We will use what we learn here and the information we collect in other projects.’ So far, OWP12 has resulted in about 60 new projects for D&S. Various applications and findings that resulted from OWP12 are being applied elsewhere. From the start, the company has endeavoured to do everything ‘right’. That means that in developing its own new headquarters for the long term, it has opted for sustainable solutions. But it also meant that this should not be more costly than other buildings. ‘This building was developed at the same cost as comparable buildings,’ says Szeidl. ‘Maybe the design was 10% more expensive. However, using new methods in developing and building made it cheaper.’

Use of BIM (Building Information Modelling) created a digital twin of the building that allowed designers and engineers to work on all aspects of the project from behind a computer. It also enabled the use of prefab methods as much as possible. From manufacturing the builders borrowed the just-in-time principle. ‘This is the wave of the future,’ says Szeidl, ‘preparing off-site as much as you can always saves money.’ D&S also devoted a lot of time and energy to Cradle to Cradle principles, aimed at avoiding the production of waste. Under the C2C philosophy, ‘waste is a design flaw’ – that is to say, there should be no waste from the start. C2C goes a step further than just recycling; if from the start all building parts are designed with a second life in mind, there will be no waste at all. In OWP12 Drees & Sommer claims to have achieved a Cradle to Cradle score of about 70%, but promises that 100% is possible in about five years’ time. ‘In construction, individual solutions still make up 80% of the work, whereas standard solutions amount to 20%,’ Szeidl explains. ‘It should be the other way around.’ This is not to criticise the construction workers, it is just part of the evolution of building, he says. New designs that meet the C2C requirement may at this point still be too expensive. Over time, however, prices will go down.

Checking the walls
The plot of land that Drees & Sommer was able to secure for its new project was not ideally situated. At a distance of about 100 metres lies the 831 motorway, connecting Stuttgart to nearby Sindelfingen, home of Mercedes Benz. The constant noise emanating from the traffic racing by added to the sustainability challenges for D&S. Not only did the walls of the building have to insulate cold and heat, but also sound. The solution the designers and engineers came up with turned out to be vacuum insulation, turning the building into a sort of Thermos flask. The thickness of the walls was limited to 90 millimetres, where 340 is considered normal. The solid part of the walls is made of calostat, a silicon foam that is 100% recyclable. Surprisingly, standing inside the building and looking at the cars racing by, one hardly hears anything. A calculation of how much space is saved and money gained by having walls this thin amounts in the event of a sale to a higher profit of €3,800/m² in an office building with 15 floors of 600 m² and a façade area of 5,250 m². The space gain would be 345 m² because of the slim façade. The extra revenue in the event of a sale would be €1.26 mln.

‘All the technology we use is available,’ says Johannes Hopf, engineer and manager of building performance. ‘We are just cooking a new meal with old ingredients.’ 
The new OWP12 building is powered by geothermal energy and has solar panels on the roof and the façades. The roof generates 67% of the energy that is produced, while the south and west façades contribute 24%. There are even solar panels in the glass of the windows. The total output of the photovoltaic system is 243 kWp. Says Hopf: ‘The first months were better than expected. We produced more energy than we had forecast.’ The costs of the photovoltaic system will pay off in 10 to 12 years, according to Hopf – maybe even earlier given the current rise in energy prices. The building has no CO₂ emissions when in operation.

Part of the façade on the north side of the building consists of plants, with a hemp basis. Plants’ benefits are well documented: they absorb carbon dioxide and produce oxygen, plus they stimulate biodiversity. While this certainly adds to OWP12’s green look and appeal, no bees were noted during PropertyEU’s visit. Another proven benefit of the presence of plants is that they offer extra coolness during hot weather – reducing temperatures by five to six degrees. They also have the ability to self-regulate: the hemp and the plants are able to hold water for a few days. And in terms of maintenance, costwise the green façade is no different to the other walls or windows.

Drees & Sommer developed a Building Circularity Passport and a Building Material Scout for its new HQ building.  However, it was really difficult at times to find out how certain materials were treated. The aluminum in OWP12 is recycled and the three-layer carpet consists of recycled polyamide fishing nets. When it starts to show signs of wear, the carpet producer takes it back and even pays for it. The German firm is keen to apply the knowhow gained from the Stuttgart HQ building to other projects, such as the residential Moringa project in Hamburg, where a lot of wood is used, and the World Trade Center ZIN in Brussels, a mixed-use renovation project comprising offices, residential and a hotel where Cradle to Cradle techniques have also been applied.

Worker wellbeing
It was also involved in the development of the city hall building in Venlo in the Netherlands, a Cradle to Cradle project that was completed in 2016. A lot of attention was devoted here to improving the air quality, both inside and outside. A green façade reduced sulphur and nitrogen oxide outside, the University of Maastricht found. Inside the building, better air quality as a result of the use of the right materials significantly reduced sick leave among employees. Absenteeism due to illness went down from 6.2% to 4.7% – a significant drop. In a hypothetical situation where 500 workers each work 200 days a year, that would save 1,500 sick days. According to Szeidl, busloads of designers, architects and developers from all over Europe have travelled to Venlo to see the city hall for themselves.

Among the smart solutions being used in OWP12 are light and motion sensors, so that sunlight is optimally used and the sensors only light up rooms that are in use. This saves energy because lighting is reduced by 10%. Heating is also regulated; sensors automatically adjust the temperature when a room fills with people and it gets warmer. Of course, no one should feel cold so users can interfere with the automated system. ‘Employees are really happy they can adjust the lighting and heating on an individual basis,’ says Christof Göbel, lead IT expert. ‘Things we come up with have to be helpful. The human being takes centre stage, not the building.’ According to Szeidl, the thinking on how to organise work changes about every seven years. Drees & Sommer is aware of that and stresses that OWP12 is meant to be flexible and adjustable. The way it was designed, for instance, allows the building to be split up for up to seven users.

Apart from that, even working in the office itself is not a given anymore since the pandemic. ‘We can work anywhere,’ attests Rowena Johnston, team leader of user experience. ‘The office has definitely lost its monopoly.’ As a consequence, the office has to compete with other spaces. More time and effort have to be devoted to workers’ wellbeing: do they want to stand up or sit down when working? How much space do people need? In OWP12, four desks are grouped in a block and there are eight to 12 desks in a room. In Germany, ‘people don’t like to be squished and squashed in a room’, says Johnston, who is Australian herself and a 12-year veteran at D&S. ‘Already in this new building we can see what works and what doesn’t.’ Since December several adjustments have already been made. For example, the temperature on the third floor turned out to be slightly higher than on other floors, but that was easy to fix. OWP12 therefore remains a work in progress, a laboratory where D&S can monitor its own office use and learn.

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