Vienna is growing and with it the need for new buildings, but there is hardly any space left for them. Development implies that the old buildings will be demolished and replaced with new ones. However, another solution should be found on how to deal with the existing buildings, as demolition this is not an adequate solution in times of climate change and resource scarcity. The topic of conversion and extension will, therefore, play an increasingly important role in the architecture of tomorrow. This applies above all to high-rise buildings, since a large amount of material is used here.
The APA high-rise is located in Muthgasse, which has been vacant for many years. It has already been through numerous changes of ownership and, therefore, is a sign of poor urban development. The City of Vienna has a masterplan in which they intend to demolish the high-rise and replace it with a sustainable high-rise complex consisting of five buildings rising up to 80m in height. However, it is not sustainable to demolish a well- preserved existing building, only to build another that is almost as tall as the previous one on the same site. The most sustainable building is the building that has already been built. This raises the question of how the existing high-rise can be transformed sustainably, so that it can be used for decades.
The design proposed keeps the flexibility of the existing building and can be used for both residential and office spaces or in combination. The skeleton structure is reused, strengthened with a steel skeleton, and expanded with a wooden structure on the outside. The facade consists of an openable winter garden, which provides protection against wind and various weather conditions and serves as a buffer volume.
As a result, the building has the best design for prolonged use and, if necessary, adapted in the future. Thus, the negative example becomes a role model for sustainable building transformation.