The Neanderthal Museum Foundation operates a museum at the world-famous site of the Neanderthal discovery, offering an innovative exhibition concept and a wide range of educational programmes that attract a broad public. The museum building itself is a landmark: a closed, elongated oval concrete structure, clad with a distinctive glass facade, and characterised by a gently rising ramp that emerges from the ground.

By 2019, the need for a full renovation of the facade had become evident due to moisture ingress and visible moss growth. An expert report concluded that the glass facade, originally built in 1996, required comprehensive refurbishment from base to roofline. Over time, open sealing joints, unsealed connections in the U-profiles and metal cladding, and blocked drainage holes had allowed rainwater to penetrate behind the glass elements. This led to extreme algae and mould formation inside the facade, driven by a “greenhouse effect” caused by the open-ended glass panels and trapped moisture. In addition, metal cladding between the glass profiles had become warped due to stress, leaving joints insufficiently sealed.

Preserving the building’s appearance posed a particular challenge. The original cast glass in its distinctive green tone was no longer commercially available. Standard replacement glass would have altered both colour and dimensions, significantly changing the building’s appearance. The solution was the development of a custom-made BIPV (Building-Integrated Photovoltaic) facade, combining the original aesthetic with modern solar technology. Test installations of matt, green-tinted glass confirmed that the distinctive look and geometry could be retained while integrating photovoltaic modules.

During the renovation, the entire facade was dismantled and rebuilt. The existing steel support structure was largely retained, while aluminium-clad insulation was repaired to improve thermal performance. Photovoltaic glass modules were installed on parts of the south, east, and west facades, with matching non-PV glass used on the north side. In total, 735 glass elements were installed, of which 248 contain PV technology. The modules were supplied by Sunovation, a leading manufacturer of architectural solar glass, whose SCET silicone filling process ensures high performance and long service life.

The new multifunctional facade now acts as the building’s protective envelope while generating over one-third of the museum’s annual electricity needs for direct on-site use. Its matt green colour was custom-matched, ensuring the unique visual identity of the building remains unchanged. Depending on sunlight conditions, the glass creates a dynamic interplay of light and shadow, giving the facade depth and elegance.

This renovation is part of the museum’s broader mission to preserve the past with a view to the future. The works also included roof and skylight improvements, enhancing energy efficiency and the building’s long-term resilience. The project was planned and tendered in 2023, executed in 2024, and completed by the end of the year.

Funding was provided by the Federal Government Commissioner for Culture and the Media (Investments in National Cultural Institutions), the Ministry for Home Affairs, Municipal Affairs, Building and Digitalisation of the State of North Rhine-Westphalia (Heimatzeugnis programme), the District of Mettmann, and the North Rhine-Westphalia Foundation for Nature Conservation, Heritage, and Culture. The Neanderthal Museum Foundation extends its gratitude to all funding partners for making this project possible.