The new headquarters of the Gesellschaft für internationale Zusammenarbeit (GIZ) in Eschborn near Frankfurt is a 6-story building. The ground floor consists of public spaces (restaurant, atrium and auditorium etc), while the upper floors are for office space.
The main goal of the building was to achieve a very high level of comfort while minimizing energy demand. The building will meet the target "DGNB Platin".
To reduce heat loads and overheating of the building, the upper floors have an optimized window-to-wall ratio and movable external screens that also serve as glare protection. The ground floor is almost entirely glazed but is covered with 50% serigraphy. Thanks to the efficient facade, all office spaces offer very good daylight quality: Mean Daylight Factor is above 2% and continuous Daylight Autonomy (cDA) above 60%.
Office spaces are conditioned with innovative radiant systems: Innogration© activated slab. In addition to heating and cooling functions, acoustic absorbers are integrated in the slabs. Therefore, the office spaces do not require additional acoustic panels and the thermal mass of the concrete ceiling remains fully visible. This enhances the inertia of the building and its passive cooling capacity: The operative temperature in the offices is always under 27° C (80,6° F). Fresh air is supplied by a displacement ventilation system with heat recovery: In combination with a very performant envelope, this results in a very low heating demand.
Extensive thermal simulations and Computational Fluid Dynamic Simulations have been carried out on the atrium, to assess its comfort both in winter and summer. Its glass roof has photovoltaic screen printing (ca. 50 kWp), producing renewable electricity while reducing heat gains in the atrium. Natural ventilation during shoulder season and night ventilation, combined with a floor heating and cooling system, make the atrium comfortable even during summer temperature peaks.
Boreholes are connected to a reversible geothermal heat pump, which provides low temperature heating and free cooling for the building. High temperature heating is obtained with a biogas boiler, while cooling for the mechanical ventilation and the servers is achieved by a chiller.
Overall, over 75% of the heating energy and 50% of the building cooling energy is provided by geothermal energy. Around 300 m² photovoltaic panels (60 kWp) on the roof produce renewable electricity. Together with the electricity produced by the monocrystalline cells integrated on the atrium’s glass roof, 50 t CO2 are saved every year.