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====== Passive House City District Heidelberg-Bahnstadt - Experience and Evaluation ======

//Author: Ralf Bermich. This article is the paper presented at the 23 International Passive House Conference 2019 in Gaobeidian, China. //
===== Introduction =====

In 1992, the city parliament of Heidelberg adopted the first municipal climate protection concept. It was worked out by the Institute for Energy and Environmental Research Heidelberg (ifeu) with intense participation of citizens and stakeholders. It analysed energy consumption and CO<sub>2</sub> emissions from households, industry, trade, crafts, public institutions (university, hospitals, administration) and the mobility sector. Strategies and measures were developed for all sectors. The key focus was the reduction of the heating energy demand, because 40% of CO<sub>2</sub> emissions from energy consumption in Heidelberg were caused by space heating. The City of Heidelberg committed itself to integrate energy efficiency and climate protection into all activities of the administration. Since 2010 all new municipal buildings meet the Passive House standard. Furthermore, energetic retrofit programmes, transformation strategies towards efficient and renewable energy supply as well as awareness raising programmes were introduced. The City of Heidelberg is committed to sustainable development goals and is engaged in numerous city networks on climate protection like Energy Cities, Climate Alliance, ICLEI, Compact of Mayors and C40.

 [{{ :picopen:fig1_aerial_view.png?600 |Figure 1: Aerial view of Heidelberg-Bahnstadt, photo Kay Sommer}}]
===== Heidelberg-Bahnstadt - a sustainable district on former railway ground =====

The freight and switch yard in Heidelberg was no longer needed when logistic concepts for freight transport changed and was therefore closed in 1997. In 2001, an urban planning competition for the master plan of a new city district on this area was announced, and the proposal from Trojan + Trojan, Darmstadt, won the first prize (Figure 2). The concept, which picked up on the geometric structure of the railway lines in designing streets and green spaces, served as the basis for the new urban district Heidelberg-Bahnstadt covering 116 hectares. In 2007, a dynamic development started when the Mayor of Heidelberg initiated the foundation of the Entwicklungsgesellschaft Heidelberg (EGH, Development Agency Heidelberg) in cooperation with the municipal savings bank (Sparkasse Heidelberg), the city’s own housing association (GGH) and the real estate subsidiary of the state bank of the federal state of Baden-Württemberg. EGH purchased the former railway plot from the real estate subsidiary of the German railway company Deutsche Bahn and became the development agency and contracting party of the city in the urban development contract for the Bahnstadt.

[{{ :picopen:fig2_master_plan_heidelberg.png?600 |Figure 2: Master plan of Heidelberg-Bahnstadt,\\
map: City of Heidelberg, based on a draft from Trojan + Trojan}}]

In 2008, urban planning competitions were held for the ‘Wohnen an der Promenade’ residential area and the ‘Campus II’, where student dormitories, educational facilities and research-intensive companies are located. These two areas constitute the core of the first construction phase of Bahnstadt. Construction of the first residential projects began in 2011, and the first plot was finished in 2012. Marketing of the residential untis was very dynamic from the beginning. Estate agents reported that for many of the new inhabitants in the Bahnstadt, the Passive House standard and sustainable concepts were decisive. At rpesent, 4.500 inhabitants are living in 2.500 apartments. When finished, about 6.800 inhabitants will be residing in about 3.700 apartments.

As a conversion area and because of its central location, the Bahnstadt is an excellent place for sustainable urban development. In accordance with the City of Heidelberg’s climate protection and sustainability goals, professional concepts for various environmental aspects were worked out. Because of its proximity to the central train station, the Bahnstadt offers good potential for the use of local and long-distance public transport. Two tram lines were realized connecting the Bahnstadt to the rest of the city, and bike paths on former freight train lines link the Bahnstadt to neighbouring districts without any intersections with car roads. Within the next years, two pedestrian and bike bridges will cross the railway lines and the river of Neckar, providing attractive connections besides car traffic.

[{{ :picopen:fig3_schwetzinger_terasse.png?600 |Figure 3: Residential buildings and municipal kindergarten Schwetzinger Terrasse in Bahnstadt, photo Christian Buck}}]

Soil management minimised the amount of soil transfer. Green spaces and green roofs protect nature and improve the urban climate by means of evaporative cooling, and rainwater is retained so that the amount of rainwater that enters drainage systems is reduced.

===== Energy concept for Bahnstadt: Passive House standard and district heat =====

Together with the engineering company ebök, an energy concept was developed for the Bahnstadt [ebök 2007]. Various building standards and heat supply variants for the building structures in the master plan were assessed in terms of CO<sub>2</sub> emissions and costs. On this basis, Heidelberg’s city council decided to make the Passive House Standard and heat supply via district heat obligatory for the entire Bahnstadt district. District heat and electricity are produced by the municipal supplier Stadtwerke Heidelberg in a wood-chip-fired CHP, using wood from regional sustainable forestry. This makes the Bahnstadt a zero-emissions district. To encourage rational electricity use, a power-saving concept has been worked out [Stadt Heidelberg 2012]. The energy concept is specified as a development goal for the Bahnstadt and was made binding through regulations based on building law and contractual instruments [Bermich 2013]. Intensive PR work and sophisticated quality assurance in the planning and construction phases were decisive towards compliance with the Passive House standard [Persch 2013].

The city of Heidelberg and the municipal energy agency offer energy advice to all investors in the early stages of planning to explain the benefits and concept behind the Passive House standard as well as the reporting and control systems. Passive House calculation using the PHPP is required as part of the building application, together with building energy concepts covering insulation, airtight construction and ventilation.

===== Evaluation of energy consumption for space heating =====

The ciy of Heidelberg comissioned the Passive House Institute in Darmstadt with the evaluation of the district heat consumption for space heating in the residential buildings during the first stage of construction of the Bahnstadt. the monthly heat measurements of the municipal energy utility Stadtwerke Heidelberg for the building plots. All building plots, each comprising about 100 apartments, have one district heat transmission station with a heat meter.  Total district heat consumption was directly measured, including space heating, hot water for showers and kitchens, and standby losses of installations and heating lines. The pure heat consumption was calculated taking into account the summer consumption in those months without the speace heating demand. This analysis is described in detail in the publication monitoring energy consumption in the new district Bahnstadt in Heidelberg  [Peper, Persch 2016].The analysis showed a variety of specific space heating consumptions between 9 and 27 kWh/m<sup>2</sup>  a per square metre of heated floor space for the different projects. The mean value for all analysed apartments was 14.9 kWh/m<sup>2</sup>  a in 2014 and 16.4 kWh/m<sup>2</sup>  a in 2015, thus complying with the Passive House standard.

For the following years 2016 – 2018, the city commissioned the regional energy agency KliBA with energy monitoring using the same method. Due to the growth of the Bahnstadt, a greater number of plots could be analysed. The results of the analysis for 2014 – 2015 were integrated into the report [Orlik 2019]. Figure 4 shows the specific heating consumption (without ambient temperature compensation). Each residential building plot is indicated by an anonymised marker BS-xy. The columns indicate the specific heating energy consumption per square metre in the years 2014 -2017 showing a range from 9 kWh/m<sup>2</sup>  a up to 25 kWh/m<sup>2</sup>  a (ignoring the extreme outlier BS-20). In view of the fact that the actual room temperature in winter is typically in the range between 21° to 22°C, the mean value correlates well with that for the Passive House standard.

[{{ :picopen:fig4_heating_consumption_residential_bahnstadt.png?600 |Figure 4: Total specific space heating consumption of residential building projects in Bahnstadt in 2014 and 2017 [Orlik 2018]}}]


===== Discussion and conclusions =====

Bahnstadt is the largest Passive House dsitrict worldwide – may be Heidelberg must hand over this title to a Chinese City soon. Passive house standard is obligatory in Heidelberg-Bahnstadt for all kinds of building. Energy concept, technical advice and quality assurance during planning and construction phase are main success factors. A questioning showed, that inhabitants are satisfied with living in a Passive House. Evaluation of heat consumption per square metre showed mean values matching Passive House standard.

===== References =====

[Bermich 2013] Bermich, R.: Urban development with Passive House Standard – Heidelberg’s new Bahnstadt district grows dynamically, Proceedings of the 17th International Passive House Conference, Frankfurt 2013

[ebök 2007] ebök Ingenieurbüro für Energieberatung, Haustechnik und ökologische Konzepte, Hildebrandt et al.: Baugebiet Bahnstadt in Heidelberg – Städtebauliches Energie- und Wär¬meversorgungskonzept, Tübingen 2007

[Peper/Persch 2016] Peper, S.; Persch, R.: [[examples:passivehosue_district:passive_house_district_heidelberg-bahnstadt_monitor|Monitoring energy consumption in the new district Bahnstadt in Heidelberg]], Proceedings of the 20th International Passive House Conference, Darmstadt 2016

[Persch 2013] Persch, R.: Quality management system for Heidelberg’s Bahnstadt Passivhaus district, Proceedings of the 17th International Passive House Conference, Frankfurt

[ebök 2012] Hellmann, R. (ebök), Rath, U. (CONSISTE), et. al.: Stromsparkonzept Bahnstadt – Electricity saving concept Bahnstadt, editor: City of Heidelberg, Office for environmental protection, trade supervision and energy

[Orlik 2019] Orlik, W. (KliBA): Heidelberg Bahnstadt - Survey of the Energy Consumption 2014 – 2017 and preview 2018, Passive House Conference “Besser Bauen”, Heidelberg 2019

===== See also =====

[[:examples:passivehosue_district]]

[[:municipalities]]

[[examples:passivehosue_district:Passive House district Heidelberg-Bahnstadt|Passive House district Heidelberg-Bahnstadt in the eyes of its residents]]

[[examples:passivehosue_district:Passive House district Heidelberg-Bahnstadt monitor|Monitoring energy consumption in the new district Bahnstadt in Heidelberg]]