Westspitze Gewerbebau GmbH & Co. KG, in which UmweltProjekt GmbH (a subsidiary of Umweltbank AG Nuremberg) holds a 50 per cent stake, while around 10 private investors from Tübingen and the surrounding area hold the remaining 50 percent, wanted a building with high ecological standards and requested the use of wood for the supporting structure. In terms of energy efficiency, the KfW 55 standard was to be met, which according to Oliver Braun, Managing Director at a+r Architekten and responsible for the Westspitze project, “is a demanding objective for an office building”. Electricity was to be generated using photovoltaics, and the aim was to develop a durable and low-maintenance façade cladding.

The architects of the “tower” shimmering in warm earth tones, which was ready for occupancy in September 2020, faced a whole series of challenges at the beginning of the design process, starting with the oblique-angled site. “For an efficient timber or timber-concrete structure, right-angled ground plans with moderately large spans are actually particularly favourable,” Braun explains. The architects solved this requirement by designing a concrete base with dark clinker facing and integrating a triangular core built of reinforced concrete in the centre, which accommodates the staircase and lifts. This “core” provides sufficient stiffening and makes it possible to connect rectangular timber floor slab elements. The façade design also required an innovative solution. The client wanted photovoltaic elements to be integrated into the façade, which had to have an aesthetically appealing design. 

a+r Architekten succeeded in creating an energy-generating façade without making it look “too technical, which would certainly have been the case if classic PV modules had been integrated,” explains Oliver Braun. The architects chose colour-coated PV elements that were integrated into a curtain-wall façade made of powder-coated aluminium sheets, oscillating in different colours depending on the incidence of light. These innovative thin-film solar panels convey a certain emotionality with their bronze-coloured shimmer. The entire façade geometry had to be very precisely matched to the requirements of the timber supporting structure. A total of approx. 1,100 cubic metres of solid spruce from the northern Black Forest and Upper Swabia was used for the exterior walls and floor slabs – according to the architectural office, this is “more than 1,000 tonnes of permanently bound CO2* – plus the CO2 savings compared to building with reinforced concrete”. Steel and concrete were only used where necessary: the floor slabs, for example, consist of a timber-laminated composite with a seven-metre span (20 cm thick) and a top concrete layer of only 10 centimetres.

“A seven-storey office and commercial building that was constructed from the first floor upwards as a timber hybrid structure can certainly be described as innovative,” is Oliver Braun’s assessment – even though timber hybrid construction is now being given greater focus as an ecological alternative to conventional building materials. a+r Architekten admit that the innovative and sustainable construction method for this building resulted in a good 20 percent extra costs than would have been the case with a conventional building. Planning was much more complex and it was rarely possible to use standard solutions. However, these additional costs were borne by all those involved – and the client, in particular, has considered the high ecological quality to be essential in order to market and rent the building accordingly. The commercial tower tower has been fully occupied since October 2020. Tenants include the renowned World Ethics Institute, consulting companies, medical practices and a provider of co-working spaces.

The interior design with 4,500 square metres of commercial areas is also an expression of the climate-friendly construction method. Vertical gardens welcome visitors on every level with staghorn ferns, orchids and other rainforest plants that evoke immediate well-being and radiate a pleasant greenhouse atmosphere. The partially visible wood composite construction on the underside of ceilings and the supports along the façade, where wood was left visible, are equally appealing to the senses. Floor-to-ceiling glazing allows plenty of daylight to enter the interiors and creates a feeling of spaciousness. A large hall on the ground floor offers a variety of options for congresses, events and all kinds of cultural activities, while on the 7th floor a large common room with terrace is available to all tenants of the Westspitze, who can enjoy a spectacular panoramic view from here.

At the back of Westspitze, further construction work was carried out. According to a design by a+r Architekten, a residential quarter with a total of 106 1- to 5-room flats along with a supermarket and a commercial unit was built in the area of Reutlinger Strasse, Josef-Wochenmark-Weg and Hanna-Bernheim-Strasse, and completed in November 2020.

Source: https://www.holzbau-deutschland.de/mit_holz_bauen/holzbau_und_klimaschutz/co2_verbrauch_in_zahlen/

Planning and construction period: 2018 - 2020
Planning office: a+r Architekten GmbH
Client: Westspitze Gewerbebau GmbH & Co. KG
Project address: Tübingen

With around 130 employees across its offices in Stuttgart and Tübingen, a+r Architekten is an established architectural practice in southern Germany. Led by Oliver Braun, Florian Gruner and Alexander Lange, the practice works across a broad range of building types, from educational, cultural, sports and religious buildings to administrative buildings, housing and urban developments, as well as projects for industry and commerce.

For more than 40 years, a+r Architekten has developed architecture through a close engagement with context, brief and existing structures. The focus is on appropriate, functional and durable solutions. The preservation and transformation of existing buildings, resource-efficient construction and the considered use of materials play a central role in the practice’s work. a+r Architekten has received numerous awards for its architecture.

www.aplusr.de

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