A new city district of 116 hectares is growing on an abandoned area of a former freight yard in Heidelberg. This area will be transformed into a district which is being developed considering multiple aspects of environmental protection. 5,000 citizens will find a place to live and 7,000 new jobs will be created. This development is an on-going process which started in the year 2008 and is scheduled for completion in 2022. To date most of the areas are sold and the majority of the planned residential buildings has already been constructed. The main project idea has always been to create a mixed space for living, research and work. Accordingly, some office buildings and trade facilities were built in parallel with the residential buildings and are being used by high-tech and science companies.
The Energy Concept of Heidelberg Bahnstadt
The second and perhaps even more outstanding idea has been to create a showcase-district to prove the feasibility of high energy-efficient building and a sustainable energy supply. All buildings in Bahnstadt have to be constructed in accordance with the Passive House Standard. A dense insulation of walls, roofs and windows keeps the heat inside the buildings. The orientation determined by the sun helps to use as much solar power as possible for passive heating. A well elaborated ventilation system with heat recovery offers a high air quality and uses the warm exhaust air to heat up the fresh air, again saving energy. The threshold to become a passive house is an overall energy demand for heating of maximum 15 kWh per m² per year (approximately 10% of the average heat demand of the existing building stock in Germany). To implement these ideas in the construction of new buildings, all partners (municipal institutions, investors, developers, architects, engineers, construction workers) were informed about challenges during construction. An evaluation of the energy consumption after the first two years in usage showed that the energy demand of the residential buildings in Bahnstadt complies with the Passive House Standard and the feedback of the inhabitants is mainly positive.
The City of Heidelberg aims to supply the energy still needed in a CO2–neutral way. The first step towards this ambitious goal was to connect the whole district to the existing urban district heating system. The second step is to run this district heating system on renewable sources. A combined heat and power plant (CHP) fed by wood chips started operation in 2014. This power plant is connected to the main grid but, in a stand-alone solution, its thermal and electrical power output would be high enough to cover the whole energy demand of Bahnstadt.
View of one of three daycare centres in Bahnstadt and one of the main squares “Schwetzinger Terasse”; Photo credit Stadt Heidelberg/Ralf Bermich
Environmental Protection Measures in Heidelberg Bahnstadt
However, the high energy-efficiency standard is not the only aspect of environmental protection borne in mind during the development of the Bahnstadt district.
A sophisticated soil management scheme helped to reduce the impact of transportation to and from the construction site. Soil removed from areas where construction is in progress was transferred to areas where no construction was going on, but remained inside the project area. Due to this, no lorries where driving through the existing city districts. Fuel saving and a minimum impact on the surrounding population were the results.
Another environmental issue accompanying all bigger construction projects is soil sealing. Sealed areas have an impact on the ground water depletion and lead to problems with the handling of rain water on surfaces. A rainwater management system is employed that helps to maintain the natural functions of the soil, with an increased proportion of rainwater being allowed to evaporate and benefiting the local climate. Therefore 66% of the flat roofs have to be equipped with an extensive green roof where up to 70% of the rain water is stored and from where it evaporates at higher temperatures. Additionally, a 710 m long pond system collects and stores water. The remaining rainwater is infiltrated into ground water.
For more than one decade the area had been abandoned and not maintained. This led to the development of a rich flora and fauna including some rare and protected species (especially lizards). Prior to the start of the construction work, amongst others, thousands of sand and common wall lizards were relocated to specially created new habitats. Areas that are of importance to local ecosystems are deliberately being undeveloped. The greened roofs (see above) also provide new habitats for plants and animals.
Project Status and Outlook
Only five years after the construction of the first residential building, 3,200 inhabitants are living in the new district. On an area of 243,000 m² constructions are finished or in progress. One third of this area is public green space. 168,087 m² heated floor area with 106,879 m² for living highlight the importance of the Bahnstadt district to improve the housing situation in Heidelberg. The second phase of the project will be dominated by the construction of non-residential buildings. These will include schools, shopping malls, a cinema, recreation centers, an international convention center, buildings with space for laboratories and offices. As all of those are non-standardized buildings, it is even more important for the municipal offices to communicate continuously with investors and architects to ensure the high energy efficiency standard of the building and therefor to minimize the carbon footprint of a whole urban district.
City of Heidelberg
Office of Environmental Protection, Trade Supervision and Energy
Phone: +49 6221 58-18000
Ask for: Ralf Bermich; Robert Persch, Fabian Nagel