Weingarten is a city district in Freiburg which was built between 1960 and 1965 and consists of four types of buildings: 16-storey high-rise buildings, 8-storey and 4-storey blocks of flats. In Freiburg the public company Freiburger Stadtbau GmbH is in charge of managing social housing in the city. The Weingarten area is undergoing renovation which started in 2007 and is planned to be completed by 2018. The renovation of the first 16-storey high-rise building was completed in 2011 and this was the first residential high-rise building worldwide to reach Passive House standards through renovation. The works dealt with refurbishing the building envelop (achieving U value between 0.11-0.13 W/m2K), installing new balconies, photovoltaic systems and fire protection. Moreover, the heating system of the building was connected to the district heating available in the area. Thanks to the refurbishment, the heating requirement achieved in the building was 15 KWh/m²yr (EnEff, 2014). Figure 1 presents final and primary energy demand before and after renovation of the high-rise building. It is interesting to see the great reduction for heating demand and distribution losses thanks to the refurbishment.
Figure 1: Primary and final energy demand, before and after renovation of the high-rise building in Freiburg
When planning the refurbishment of the high-rise building in Weingarten, it was decided to reduce the size of flats, since nowadays, compared to the '60s, average families are smaller. Consequently, from 90 flats before the refurbishment, 136 were the flats obtained at the end of the works. In order to engage with residents, Freiburger Stadtbau GmbH, after the refurbishment, organised some meetings with tenants in order to explain the features of the passive house flats, together with guidelines and tips on how to best use them.
The cost for the refurbishment of the first high-rise was about 13 million € which correspond to 1700€/m2, while, for the following buildings it is estimated to be about 1500€/m2.
Figure 2: Refurbishment of 16 storey high-rise building in Freiburg (EnEff, 2014)