Built in the sixties, the “Rosengarten” at the Dornacherplatz square in Solothurn underwent renovation to meet the needs of the cantonal administration, and was reopened in 2022 after a two-year construction period. RIVULETTA® ribbed structure glass from SCHOTT was used for energy-efficiency refurbishment of the distinctive façade.

The challenge
Extensive renovation of the “Rosengarten” was intended to create a modern, future-ready office building.

The distinctive façade with its characteristic features such as the louvred aluminum and glass façades and the smooth concrete panels was to be given a new architectural outfit without radically changing the original look.

Background
The “Rosengarten” building dates back to the 1960s and was built in a skeletal structure design. It has two lower and five upper floors as well as a rooftop level. The site area is 1,312 m² with total floor space of around 7,000 m². Initial strategic discussions took place in 2006, and in 2012 the property was acquired by the cantonal government for use as an administrative building. Refurbishment was finally approved in 2016.

Characteristic for the external appearance and in particular for the fully glazed, twelve-story square façade were the evenly gridded glass sections alternating with windowless wall sections of raw exposed concrete. Thin aluminum profiles held dark blue-green parapet glass alternating with transparent window glass, which was mounted flush between the load-bearing wall sections as a curtain wall.

What needed to be retained was the original contrast between the steel and glass façade elements and the solid wall panels, as well as the façade’s balanced horizontal and vertical proportions.

The solution
Architect and site manager Roger Stucki was tasked with planning the major renovation. The project was implemented by Fahrni Fassadensysteme AG from Lyss in Switzerland.

The Spanish architectural glass company Tvitec produced laminated safety glass comprised of RIVULETTA® color-coated structured glass and float glass, each with a thickness of 6 mm. Both types of glass were also partially thermally tempered. In the images, these façade elements are the green glass parapet elements below the windows.

Post-renovation, this has retained the visually interconnected façade fields between the exposed concrete and panes, as well as the structure exterior identity. The band of vertical glass louvers on the south side, known as the “spoiler”, links with the extra height of the first floor, which previously housed a shop. The “Rosengarten” lettering printed on the louvers displays the building’s name and, for viewers from the Dornacherplatz, creates a visual interplay of lettering whose legibility change depending on the daylight.

The renovation also focused on sustainability. Preserving the concrete structure alone saved around 1,500 tons of carbon dioxide. The building’s energy efficiency was improved by 30 to 40 per cent.

Sixteen years have passed from the initial strategic discussions up to the completed “Rosengarten” conversion. In August 2022, after two years of construction, the building was reopened as the new headquarters of the education and culture department. The department’s staff, numbering around 120, are now housed together under one roof. This has benefits for everyone.

The material
230 sheets of laminated safety glass made from thermally tempered glass (laminated safety glass from thermally tempered glass) composed of the following:

• SCHOTT RIVULETTA® 6 mm with green screen printing on the back, laminated safety glass
• PVB film 1.52 mm
• Float glass 6 mm thermally tempered glass
• Ground edges (KGN)

A total 105 sheets of RIVULETTA® from SCHOTT (2,500 mm x 1,500 mm) were used.