Posttower Deutsche Post AG, Bonn, Germany

Posttower Deutsche Post AG

The prestigious administrative building with a 40-story fully glazed office tower and base building stands on a plot of land near the banks of the Rhine River. The requirements for flexibility and workplace quality were high. High workplace quality is achieved through natural lighting and ventilation; usability is provided by operable windows and limited individual heating and ventilation control. The desire to minimize operating costs for heating, cooling and ventilation is met by utilizing natural energy sources.
The climate concept uses a double-skin façade with reflective solar shading in the space between the façades. The component activation of the solid ceilings takes care of the basic temperature control of the building. A groundwater well is used for cooling. Heat is also extracted from this well during the heating period. If this is not sufficient, the building is connected to the local district heating system.
Decentralized supply air units are integrated into the façade. Fresh air is brought into the offices from the double façade through these underfloor units, while being individually pre-heated or pre-cooled in the unit. In addition, individual window ventilation to the double façade is also possible.
The exhaust air then enters the corridors and is further brought into the atrium, which is divided into four sky gardens, each nine stories high, one above the other. The exhaust air, including the internal heat gains of the offices contained therein, thus warms the adjacent sky garden, which leads to a pleasant temperature there and at the same time keeps the transmission losses from the office to the sky garden low.
This ventilation system also eliminates the need for an entire floor of technical equipment, another economic plus.
The entire ventilation system has minimal pressure losses, which ensures low power consumption for the fans. Presence switches provide intelligent room control; the underfloor units only run when an office is occupied. Since it happens that up to 30% of the offices are unoccupied, this is a sensible energy-saving measure.
In addition to the individual control of the supply air temperature, the desired supply air volume can also be influenced.
As soon as the room is in "presence mode" the normal amount of air is supplied, however, the user can individually switch the ventilation to “high”, which then runs for a certain period of time on this second level. Users really welcome this, as well as the option of free window ventilation. For this purpose, the flaps in the double façade are regulated in such a way that the wind pressure on the inner façade remains so low that window ventilation is always possible. In addition, the ventilation system switches off as soon as a window is opened. No energy is wasted.
The solar shading system also benefits from the double façade. Since it is installed in the interstitial space, it remains protected from wind and weather and performs its service at all times, which reduces the need for cooling.

2014 Council on Tall Buildings and Urban Habitat (CTBUH) 10 Year Award