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Newly constructed building brings municipal administration under one roof.
© ingenhoven architects H.G. Esch
Grid-friendly building
26.04.2018

The building encircles an inner garden courtyard.
© ingenhoven architects H.G. Esch

Ground floor floor plan
© ingenhoven architects H.G. Esch

New administrative facility with energy-plus concept

In 2013, the City of Freiburg held a competition for the construction of a new central administrative facility, including town hall, to consolidate its various agencies spread across the municipal area. The objective being two-fold: to produce an outstanding architectural design and to maximise energy efficiency. Monitoring measures put into effect upon commissioning are intended to reveal whether operation of the new energy-plus building fulfils the promise evident at the planning stage.

The new six-storey building of the Freiburg town hall, based on the design of ingenhoven architects, was officially opened at the end of 2017 as the first of three planned construction phases. 840 staff members of the municipal administration now work from the facility. The citizen’s service centre with conferencing rooms and staff canteen are located on the ground floor, and the administrative bodies of the municipal administration use the various floors above.

An energy-plus building of this scale is unheard of in Europe. The City of Freiburg, the DS-Plan planning office and the Fraunhofer Institute for Solar Energy Systems (ISE) are therefore supervising the construction and operation as part of a research project. A central theme of investigation is the issue of how targets stipulated in the planning phase carry over into operation and how their implementation is verifiable.

Building and energy concept

The building is highly thermally insulated and with floor-to-ceiling triple glazing combined with external solar shading allows for the optimal use of daylight. Protruding larch timber elements with integrated PV modules provide a defining visual touch. Ground water as a heat source is used to heat the facility via heat pumps and to cool the building directly via a heat exchanger, supplemented by coolers on the roof. A biogas-fired boiler covers peak loads and ensures domestic hot water heating, required first and foremost for the canteen, in combination with solar thermal usage. The rooms are supplied with fresh air via a ventilation system with highly efficient heat recovery.

Warm and cool air is supplied to office space via concrete core activation and heating/cooling ceiling panels. Public areas are largely fitted with underfloor heating and partial air-conditioning.

Difficulties of large energy-plus buildings

An energy-plus building produces more energy via renewable sources than it actually needs for heating, cooling, ventilation and lighting. It covers its own energy requirements therefore in terms of bills. In addition to a well-insulated building envelope, this usually requires expansive solar-active surfaces. For large, compact buildings, this presents a challenge, since the usable surface area as a measure of the full extent of energy needs increases faster than the envelope area as the building size increases. Furthermore, competition for space results between solar thermal and photovoltaic systems. For this reason, both the roof and façade on the new Freiburg central administration building are used for photovoltaic electricity generation. Photovoltaic-thermal hybrid collectors (PVT) operating in sub-areas simultaneously produce electrical power and hot water for domestic hot water heating.

Challenges of grid-friendliness

While on the balance sheet energy consumption is coverable from renewable resources in zero energy and energy-plus buildings, closer scrutiny reveals a seasonal, weather and daylight-dependent disparity between supply and demand, particularly with solar energy. The increasing proportion of such fluctuating renewable energies represents a challenge for grid operation. The objective of planning therefore is to maximise self-consumption while preventing load peaks both in drawing and in feeding electricity into the supply network. Intelligent control technology is designed to support grid-friendly operation. In terms of overall consumption, the way the administrative building is used facilitates high self-consumption of PV electricity generated on the building owing to its infrastructure of EDP workstations that require electricity during the day. User electricity is not factored into energy-plus accounting.

You can find a detailed version of this news item on the ENERGIEWENDEBAUEN web portal (in German).

(dg)

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Monitoring
Fraunhofer ISE

Energy concept
DS-Plan

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