The new administration and production premises of Envola GmbH are located in the Science Park III in the Eselsberg district of Ulm. The compact building consists of two sections with two distinct supporting structures: on the one hand, we have a hall with a free-spanning BauBuche lattice girder roof construction. On the other, there is three-storey timber frame structure of the office block made with BauBuche posts and beams.
The Science Parks in Ulm bring together science and business, tapping into local resources and focusing on technologies that are in demand, and Envola GmbH is a perfect fit: the company designs intelligent storage technology for the efficient heating and cooling of buildings, especially in connection with renewable energies. In 2018, the new premises of Envola were built on the 40-hectare site of the third Science Park in Ulm, as there was no more space at the other two Science Parks in the city.
The design of the building is based on the urban development concept of the city for sites on slopes. Right above the block runs Wolfgang-Paul-Strasse. The entrance of the new building is located at the level of Max Born Strasse. The difference in elevation between the two street levels is reflected in the height of the building sections, and the architects made sure that the view from Wolfgang-Paul-Strasse over the Schammental valley remained unobstructed. This was achieved by placing the long side of the 10 m high block parallel to the street and into the slope. Together with the smaller wing to the west, this block provides ample space for a large entrance hall and exhibition space. Adjacent to the short side of the hall, we have the three-storey office building. While the new building houses both office facilities and a production hall, this is not instantly visible from the outside. At the inside, the building with a length of 55 m and a width of 25 m is divided into a 45 m long hall, and a 10 m long office section. The dual nature of the building is only reflected in its façade.
BauBuche for a climate-friendly supporting structure
The proprietors were looking for a building that meets the highest standards as regards sustainability, economy and design, and therefore opted for a timber construction. Although the components of this structure need to withstand a fire for 30 minutes, the designers nevertheless wanted to keep them as slim as possible. In order to span the hall width, they had to find a suitable support construction and roof geometry. The architects eventually opted for lattice girders, as they are not only elegant but also offer great material efficiency. With the exception of the top chord, all roof supporting elements are made in high-strength BauBuche, which enabled the planners to use small cross-sections and also achieve R30 fire safety.
The load-bearing system consists for rows of beams supported by two posts each. The BauBuche lattice girders are spaced at 5 m and rest on precast reinforced concrete posts. They form the supporting skeleton of the production hall. Thanks to the excellent material properties of BauBuche, the 25 m long lattice girders measure only 2 m in height and 24 cm in width. The girders are designed with a superelevation of 75 mm. The 26 cm wide and 28 cm high top chords are made from cross-laminated timber (GL28c) with a 2% slope from the centre of the hall to the eaves for roof drainage. At the supports, the lattice girders end a diagonal element that offers an aesthetically pleasing visual transition to the base structure. The girders are secured by means of slotted sheet metal plates and dowels to steel fasteners at the top of the supports. The spaces between the posts and the diagonal elements provides ample space for utility and cable ducts.
The 62.50 cm wide Lignotrend roof elements have a length of around 15 m and thus span across three lattice sections. They are screwed to the cross-laminated timber top chords and butt-joined to each other, forming stiffening roof plate across the entire hall.
The decision to use cross-laminated timber for the top chords was taken for assembly reasons, as using elements made from the same timber – spruce in this project – facilitates the installation of fasteners. As the softwood top chords only need to withstand compressive forces, it was possible to choose cross-sections that fit the overall filigree design of the structure.
The reinforced concrete posts carry most of the horizontal stiffening forces, while the timber frame construction of the external walls has no stiffening function. The actual hall was assembled first, and as a stand-alone building, and the adjacent office block is also a structurally separate construction.
BauBuche timber skeleton with stiffening blocks in three-storey office building
The office block attached to the small side of the production hall is built entirely from timber, including the elevator shaft and stairwell. The 10 m wide and 25 m deep elements form a skeleton made of BauBuche posts (w/h corner: 24 cm x 24 cm, w/h façade post: 12 cm x 24 cm, w/h interior: 20 cm x 20 cm, GL70) and beams (w/h 1st storey: 20 cm x 28 cm / w/h 2nd storey: 24 cm x 12 cm , GL70) in combination with Lignotrend for the floors and the roof (w: 62,50 cm, h: 27.50 cm). The single-span beams extend over a distance of 5 m from the partition wall of the hall to the steel girders, crossing the centre posts or internal walls along the centre axis. From there, the beams run another 5 m to the façade. They are joined by roof and floor slabs. Together with the double-shell elevator shaft and the partition wall to the hall, which are both made in cross-laminated timber, they provide the necessary horizontal and traverse stiffening. For the longitudinal stiffening of the office block, the structural engineers chose strut assemblies installed in the end fields of the two external wall planes running parallel to the hall length. These three-storey stiffening blocks are left exposed and form visually attractive elements of the supporting structure. They construction consists of BauBuche elements (w/h: 12 cm x 24 cm, GL70) connected to each other with concealed slotted sheet metal plates and dowels or fit bolts. For the connection of the stiffening blocks to the reinforced concrete base, the designers opted for slotted sheet metal plates welded to matching fasteners embedded in the concrete.
Ample light thanks to slim construction elements along the façade
The supporting structure of the hall with its 5-m grid allows for large windows along the street-facing side of the building. Equally airy and light is the adjacent office block. The filigree, high-strength BauBuche posts and beams form the backbone of the glass façade extending across all three floors and reflecting the post & beam design of the building. Both the offices and the hall are filled with light, and the façades of the two buildings are of the same attractive design. According to the architects, this approach promotes teamwork and cooperation between people working in R&D and people working in production.
Apart from the excellent working environment created by the timber construction, the building also comes with optimised room acoustics, as all ceilings are equipped with carefully chosen timber acoustic panels. They carry recessed LED luminaires that can be individually controlled via WLAN. The office space includes drop-in desks. Workers who only spend a few days a week in the office are given a roller containers for their belongings and simply pick a free workplace for the day. The building also houses a library, a Silentium or silent room and numerous video conference boxes. At the top floor, there is a lounge and a meeting space with kitchenette and break rooms accessible to all employees. From here, they can walk across a catwalk to access a patio located in the elevated section of the site.
The office and production premises of Envola GmbH is the first project completed on the site. The future development of the site envisages additional base buildings to the east and west of the Envola premises, as well as high office towers with up to nine storeys and a height of 32 m, all to be completed as timber-hybrid constructions. It is the vision of the architects to design a modern urban quarter that acts a beacon for sustainability and innovation.
– Text by Susanne Jacob-Freitag-
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