With the inscription «The Materials are Iron and Glass», the medal from the 1851 World Exhibition aptly describes the Crystal Palace. The show houses of the Botanical Gardens of the University of Bern, built a little later around 1860, could be categorised in the same way. Together with Suter+Partner Architekten, the façade experts from Lüchinger+Meyer are currently planning the refurbishment of the buildings, which must preserve the listed filigree steel structure. In order to ensure the load-bearing safety of this structure with as few reinforcement measures as possible, the weight of the roof glazing is reduced to an absolute minimum. A variant study of possible insulating glass units is carried out within the framework of the building physics and monument preservation constraints, as well as considering the radiation that is important for plant growth. The further development of glass refinement and the resulting improvement in glass properties play a decisive role in this. Lightweight and highly efficient chemically strengthened 0.7 mm thin glass from the Xensation® product family and 4 mm thick low-E coated thermally toughened glass are combined in an insulating glass unit.