Pictures of the Future      Fall 2008

Going for Greener Pastures

Siemens real estate wants to slash energy and water use in thousands of company buildings. Potential savings are illustrated by an office complex to be built in Vienna, where 65 % of the energy used for heating and cooling will be recovered.

For a company like Siemens, it pays to take a close look at buildings. The company owns more than 3,000 buildings and plants worldwide, and their energy costs amount to approximately €470 million per year. With increases in efficiency, this could be reduced considerably. Siemens Real Estate (SRE), the real estate company of Siemens AG, is tackling the issue in a systematic way. In conjunction with the Green Building Initiative (GBI), the energy and water consumption of SRE’s most important properties worldwide are set to be reduced by 20 %.

In the Green Building Initiative, SRE experts take into account the whole real estate life cycle. It begins with a requirements analysis and concept, continues with a planning stage and extends to construction, operation and demolition of a building. An important part of this is green building certification. This involves continually monitoring a construction project during its planning and realization phase and assuring the quality of the property. In the case of new building projects and redevelopment measures in European regions, SRE follows the criteria of the Green Building Program of the EU Commission (see GreenBuilding Program). The EU grants this environmental distinction when the energy consumption of a new building is at least 25 % below the value of the guidelines then in effect.

In addition, SRE satisfies the Leadership in Energy and Environmental Design (LEED) criteria, which are derived from a standard of the U.S. Green Building Council and are also widely used in Asia. Alongside energy consumption, other sustainability factors are also assessed, such as efficient use of water, indoor air quality, and the selection of materials. For example, Siemens’ newest buildings in Shanghai, Beijing and Moscow fulfill the LEED criteria.

CO₂ Reduction Program. Another component of the GBI is the "Natural Resources Management" campaign (NRM), which is designed to analyze how existing buildings are upgraded. NRM might, for example, examine the modernization of control systems for a building’s heating and ventilation systems. Such work would include replacing electric drives with higher-efficiency models. In an office building in Berlin known as "Nonnendammallee 101," for example, additional insulation and the optimization of heating and ventilation systems resulted in a 26 % reduction in heating costs. These steps also reduced CO₂ emissions by 500 t per year. This site is one of six Siemens buildings recently granted the Green Building label of the EU.

But according to GBI coordinator Rainer Kohns, there’s more to a good building than  energy efficiency. "To me, an efficient building is also one that has good acoustics and a good indoor climate—a building where the occupants feel comfortable and perform well," he says. SRE hopes to reconcile these criteria with energy efficiency. One place they want to do so is Siemens City Vienna.

Siemens City Vienna will integrate the company’s corporate units at its existing Vienna-Floridsdorf location in the north of the Austrian capital. The site covers 485,000 m²—the size of 100 soccer fields—of which 140,000 m² are occupied by existing buildings, with a new building expected to cover an additional 100,000 m². The new structure will be a 12-story central building, the Siemens Tower, which will be connected to four and five-story office buildings. In addition to rooms for conferences and special events, a number of restaurants and a cafe will be integrated into the complex.

"Our strategy is to optimize the thermal properties of the external envelope of the building so we can scale back the heating and air-conditioning systems," says Project Manager Erich Schöfbeck. When designing the building, experts used computer simulation to not only visualize the building itself, but how its systems will interact with its facade, and the effects of such interactions on the building’s thermal characteristics.

Water Pipes instead of Air Conditioning. Sustainability was also behind the decision to use a mechanical ventilation system instead of installing an air-conditioning system. Through efficient heat recovery in the ventilation system, up to 65 % of the energy employed can be reused. Occupants will be able to enjoy a comfortable atmosphere in both summer and winter. This will be achieved by means of water pipes installed in the concrete ceilings of offices. The pipes will cool the rooms in the summer and heat them in the winter. Experts call this a "thermo-active" building system.

The water cycled through the ceiling pipes will be chilled in cooling towers that will surround the building. In these towers, water will be cooled in sprinkling systems. The cooling effect will be particularly noticeable at night, when outside temperatures fall.

During the day, when room temperature rises with the number of people in the building, the use of office equipment and the sun, cool concrete ceilings will mitigate this warming and ensure a comfortable indoor climate. Concrete ceilings will thus be used as a storage medium for the coolness of the evening. In the winter, the same system will act as a heating mechanism in a similar way. Then, hot water will be pumped from the central heating system through office ceilings.

Another special feature will be a group of 26-m-deep concrete piles that will help serve as the foundation for the Siemens Tower. These "energy piles" with integrated pipe systems will use the ground as an interseasonal heat store. Water will be pumped through the concrete piles. Depending on the water temperature, the latter either transmit heat to the soil or absorb heat from it. The temperature of the ground will be the immediate source of thermo-active cooling in the summer. In the winter, a heat pump will deliver the desired temperature.

Of course, the Vienna design cannot be transferred in its entirety to other regions without modifications. "Other parts of the world have different climates and different cultural preferences. In southern regions, for example, people don’t necessarily feel like sitting next to a window. They have an abundance of sun and don’t find it uncomfortable to have a workspace in the middle of a room. And in China, for instance, there is a culture of sitting much more closely together in offices," says Kohns.

With these differences in mind, SRE has entered into a partnership with the department of Building Climate Control and Building Engineering at Munich’s Technical University (TU). Together, SRE and the TU hope to develop sustainable building designs for various climatic zones. Their long-term objective is the development of a zero-energy standard for administrative buildings. "We want buildings that have zero net CO₂ output over the course of the year. Our approach is therefore to lower their energy requirements as much as possible early on. Of course, they will always need some energy. But it could come from renewable resources such as geothermal energy, groundwater, the sun and wind," says Kohns. Only then will he consider a building to be truly green.
                                                                                                          Evdoxia Tsakiridou