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Projektinfo – Detailed information on energy research

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The new building Z3 on the Züblin-Campus in Stuttgart-Möhringen was awarded the certificate in Gold by the German Sustainable Building Council (DGNB).
© Ed. Züblin AG/Tom Philippi
Usinge waste heat
Projektinfo 06/2017

Technology concept for heating, ventilation and cooling.
© Ed. Züblin AG/Klett Ingenieur GmbH

Floor plan of the third storey: The staircase, corridors, meeting rooms, copy rooms, IT rooms, kitchenettes and toilets are located in the inner zone (red).
© zafh.net/MHM Ziviltechniker GmbH
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Servers heat office buildings

The Züblin construction group set high standards for the extension of their headquarters: in terms of construction, energy efficiency and sustainability. In operation, the energy consumed for heating and cooling is below the calculated values. The high-performance data processing centre housed in the building provides enough thermal energy to heat the building. The thermal comfort leads to a high level of satisfaction of the occupants. Most of the energy – far more than planned – is consumed by artificial light.

It was a central concern of Ed. Züblin AG to achieve the highest certification of the German Sustainable Building Council (DGNB) for its new Z3 building in Stuttgart. The building was to create a high-quality work environment for around 250 employees, and be as energy-efficient and innovative as possible in terms of its features. On the one hand, it serves as a figurehead and on the other, as a prototype. This is because the company develops and implements many such major projects at home and abroad. The experience gained from the research project can be put to use in consulting and planning. The German Federal Ministry for Economic Affairs and Energy financed a scientific monitoring with the necessary additional measuring equipment, well-grounded user surveys as well as various innovative components.

An architectural competition ensured the high quality of its design and the urban development link to the two existing company buildings. The five-storey reinforced concrete skeleton structure was realised within 15 months. The workspaces are arranged along the façade of the compact building. Glass walls separate the office rooms from the corridor, so that areas deeper within the building also receive their fair share of daylight. The exterior walls consist of prefabricated timber frame elements, which were transported to the construction site with windows, solar shading and a sheet metal covering, and were installed there. Projecting and recessed strips of untreated larch wood structure the façade in a vertical direction and contribute to shading. Externally fixed Venetian blinds provide for protection against the sun. With an average U-value of 0.4 W/m2K including the windows, the façade meets passive house requirements. A photovoltaic system installed on the green roof further improves the energy balance.

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Two chillers for the data centre

The data centre requires about 200 MWh of cooling. At low outside temperatures, free cooling can be used for the most part, and at higher outside temperatures, the chillers increasingly cover the required cooling supply. One unit is designed for heat pump operation, the other for cooling operation. During the winter months, the heat pump covers the cooling requirements of the data centre and simultaneously heats the building; this is when operation is most efficient. During the summer months, both chillers work in conjunction.

The heat demand of the building is low due to the high quality of the insulated building envelope and is almost completely covered by waste heat from the data centre. As a backup for heat supply, the combined heat and power plant of the neighbouring building is used, which is otherwise used mostly for domestic hot water heating. The heating as well as the active cooling of the office spaces is carried out primarily by capillary tube mats plastered onto the ceilings. Due to their low thermal storage capacity, they react relatively quickly and are therefore integrated into the individual room controls.

Fresh air and light regulated as required

The ventilation of the building is based on a hybrid concept. At ambient temperatures close to room temperature, the ventilation system in the office area is switched off, but the rooms are then to be manually ventilated via the windows. In the case of higher differences between outside and room temperatures, the office area is automatically ventilated with a timer. The ventilation system has a highly efficient heat and cold recovery system as well as the option of adiabatic exhaust air humidification for passive cooling. The rooms towards the interior and in the basement are only machine-ventilated. This is controlled by CO2 sensors in the meeting rooms. A ground-coupled heat exchanger and the option of free night cooling via the ventilation system raise the energy efficiency of the system.

Solar shading, lighting as well as the room temperature are presence-controlled and can be set individually using the room operating panel. Users can use a web interface to see detailed information on the operational parameters of their rooms. For example, the interface informs users about the current operating state of the ventilation system with a corresponding indicator to manually ventilate by opening the windows.

In the office rooms, only high-voltage floor lamps with direct and indirect light shares are used, which automatically adjust themselves depending on presence and ambient brightness. When the office is not occupied, presence detectors will power off the sockets to which the floor lights are connected. This prevents stand-by consumption. The lighting of the corridors and adjacent rooms also depends on presence and brightness.

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Addresses

Project management Construction
Ed. Züblin AG

Project management Monitoring
HFT Stuttgart, zafh.net

User survey
Fraunhofer IBP

Energetic assessment of the cooling supply
Hochschule Biberach, IGE

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BINE-Projektinfo 06/2017
(PDF, 4 pages, 334 kB)