Net-Zero Energy Building, Freiburg’s New City Hall

Demonstration Building – City of Freiburg’s New Administrative Center is Housed in a Grid-Supportive, Net-Zero Energy Office Building

Duration: August 2015 - December 2019
Contracting Authority/ Sponsors: German Federal Ministry for Economic Affairs and Energy (BMWi) through the Project Management Jülich PTJ
Project Partners: City of Freiburg, Badenova
Project Focus:
Freiburg’s new administrative center
© Fraunhofer ISE
City of Freiburg’s new administrative center in the construction phase.
Winning design submitted by the architectural firm ingenhoven architects
© Albert Josef Schmidt
Winning design submitted by the architectural firm ingenhoven architects, the oval building in the middle is the first of three planned construction phases.

The City of Freiburg is currently building its new administrative center (NVZ) based on a Zero-energy concept. According to present state of knowledge, it will be the largest building (ERA 23,000 m²) in Europe to date with this declared goal. A plus-energy building means that the building supplies more energy than it consumes per year, as determined in a yearly primary energy balance. The assessment limits for the annual energy balance are based on the energy demand requirements set down in the Energy Saving Ordnance (EnEV) for heating, ventilation, lighting and cooling. The user-dependent energy demand, e.g. plugloads, IT and the cafeteria is not considered in the balance. The building is to be completed at the beginning of 2017 and is the first of three buildings planned. In the course of 2017, several departmental offices located throughout the city up to now will move into the new premises. Operation of all administrative services, including the citizens’ service center shall be in full swing at the new location by fall 2017.  

Large buildings that aim to achieve a neutral primary energy balance through onsite energy generation by PV on the building envelope face particular challenges, since the useful area (thus, the energy demand) rises faster than the area available for energy generation (roof and facades). To balance out this energy consumption, nearly the entire building envelope – where feasible – is used to generate energy. Active energy generation is carried out primarily by photovoltaics, combined with photovoltaic-thermal combined collectors (PVT) and a biogas boiler. The low-temperature heating supply is based on a ground-water coupled heat pump. Heating and cooling are provided by concrete core activation in combination with radiant ceiling panels so that low supply temperatures can be used for heating. Cooling is provided almost entirely with environmental energy from the surroundings (ground water source). The hot water supply for the cafeteria and sanitary systems are supplied by a gas boiler (biogas) assisted by a solar thermal system.

One project aim is to develop and implement tools for integral planning and monitoring throughout the entire project: from the planning and tendering up to the construction phase and start of operation. Once in operation, the focus is on the dynamic load profile of demand and supply. In addition to the performance monitoring, the interaction with the supply grids will be analyzed and the possibility of grid-supportive operation will be investigated.