“Buggi 50“ – Linking technological and social innovations

November 10, 2015 Sebastian Fastenrath, Carolin Hulke

The retrofitting of “Buggi 50”, a globally recognized high-rise building project is the most recent “green” flagship project in Freiburg. The 16-storey residential building located on Bugginger Straße is the first renovated high-rise building worldwide that meets the passive house standard. The project was completed in 2011 and linked technological and social aspects.

The retrofitting of “Buggi 50”, a globally recognized high-rise building project is the most recent “green” flagship project in Freiburg. The 16-storey residential building located on “Buggingerstraße 50” is part of a large-scale urban renewal project in Freiburg’s social housing area, Weingarten-West. The area was developed in the 1960s for around 6,000 residents. It was financially supported through public funds (federal, state and local government) and Freiburg’s semi-public housing association (FSB) that initiated the urban renewal program of Weingarten-West.

The main goal of the project was the energy retrofitting and modernization of the district’s existing building stock consisting of 16-storey, 8-storey and 4-storey buildings (see map below). In the context of the federal program “Social City”, the project linked social initiatives including tenant participation and support through social workers in the planning process and beyond. The “Buggi 50” project was an important milestone of Weingarten-West’s local energy and social transition. It demonstrates the potential and importance of an integrated retrofitting concept which brings together technological and social innovations.

Social initiatives in the context of the “Buggi 50” project were essentially driven by social workers of the civic association “Forum Weingarten”, which was founded in 1989 to revitalize the district Weingarten-West.                                                                                    

Social innovations in the context of “Buggi 50” included:

  • Communication through a resident survey prior to the retrofitting process to identify relevant issues, suggestions for improvements, wishes and ideas.
  • Intensive participation, information and consultancy with residents during the planning process and beyond.
(Source: Hulke, C.; according to FSB 2009: 13)

(Source: Hulke, C.; according to FSB 2009: 13)

Facts on retrofitted buildings in Weingarten-West

The table below summarizes some important facts in the context of the retrofitted 4-storey and high-rise buildings by the FSB in Weingarten-West.


4-storey buildings

 “Buggi 50”

Heating energy consumption before retrofitting

118 kWh/m2a68 kWh/m2a

Heating energy consumption after retrofitting

55 kWh/m2a15 kWh/m2a

Heating energy savings (in %)

53 %

78 %

Achieved building standard

KfW 60 (conform to FR EH 60 2005)

Passive house

Investments by FSB per m2 1.100 €/m21.500 €/m2
Energy cost saving per m20,37 €/m20,26 €/m2
Rent increase (average per m2)1,19 €/m21,65 €/m2

Challenges - Increased costs and technological skepticism

Public criticism arose around increased rents and the potential exclusion of lower-income tenants due to the high investment costs required to achieve the passive house standard (see table). The FSB decided to increase the rent from 4,82€/m² to 6,67€/m². Nevertheless, the average rent per square meter remains below Freiburg´s average of 7,35€/m². Despite the relatively low rents, most of the former tenants didn’t move back into the renovated “Buggi 50”. Most of the tenants moved to other renovated apartments of the FSB in Weingarten and remained there. This may be partly due to the demographic structure of former Buggi 50’s tenants. The social workers of “Forum Weingarten” explained that older people in particular are not motivated to move twice within a short time period. Low return rates may also be linked to technological skepticism. For example, some tenants feared that they would not be allowed to open the windows or to use the balconies after the renovations.


The building project “Buggi 50” demonstrates that there are opportunities but also challenges in the context of retrofitting existing building stock. The level of social acceptability and increased awareness of energy efficiency of buildings play an important role in the transformation of the building sector. New business models must be conceptualized to cope with the transaction costs and develop “green” building projects that bring together energy-efficient construction and social innovations. Cooperation of all stakeholders (politicians, business, academia and organizations) can help to reduce costs for energy-efficiency as well as increase civic awareness.

More information: http://forum-weingarten.de/index.php/quartiersarbeit/weingarten-west
Fastenrath, S. (2015): 'Grünes' Bauen. Innovative Ansätze in Freiburg im Breisgau. Geographische Rundschau, 67 (5), 16-23.

Funding agencies

 Project partners

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