In 2009, the structural condition of the roof was examined more closely. Standing water within the structure made a complete renovation of the roof structure - including the replacement of the old XPS insulation and waterproofing - necessary. During the deconstruction, materials containing harmful substances were also removed. When choosing the new insulation material, a durable and safe solution with good insulating properties was required. The goal was to achieve better thermal protection and impermeability, but to maintain the appearance of the building.

The decision was finally made in favour of FOAMGLAS® cellular glass insulation. Around 4,250 m² of surface area was constructed as a durable and leak-proof compact roof with FOAMGLAS®. The insulation layer was laid over the entire surface with hot bitumen. A high-quality, bituminous two-layer waterproofing was applied above. In order not to impair the visual appearance of the roof edge, the foam glass panels were installed in a low thickness of 6 cm. Despite the slim material thickness, the minimum thermal insulation could thus be achieved. Above the waterproofing, the craftsmen applied a covering in the form of a granite gravel layer.

In order to further improve the thermal insulation and to prevent condensation in the building, insulation was also applied on the inside. Here, the fields of the coffered ceiling were lined with 12 cm thick insulation and the flanks were insulated to a thickness of 4 cm. The fastening was not done mechanically, but by means of gluing. Steel mats were mounted on the underside. 

The outdoor area - the visitors' terrace of the New National Galery - was also extensively renovated. In this area, another 6,000 m² of FOAMGLAS® slabs were used within a compact roof structure.