A sustainable retrofit first approach retaining as much of the fabric of the existing structure and facade as possible; preserving intricate detailing whilst extending the life of a building.

The 1968 listed, eight storey Miollis ‘building V’ at UNESCO’s headquarters is undergoing a quiet transformation. The building, designed by renowned architect Bernard Zehrfuss and designer builder Jean Prouvé, will be brought up to current building performance standards while retaining its architectural heritage.

Eckersley O’Callaghan won the design competition to provide structural and facade engineering with its light touch approach, to retain as much of the fabric of the existing building as possible working to maximise its potential and preserve the intricate detailing.

Rather than applying a blanket, code-based methodology to bring the building up to current fire regulation, the team have taken a more pragmatic approach. By identifying redundancy in the capacity of the original structure and working with a fire specialist, EOC has been able to safely minimise the number of elements which need to be protected. By adopting this solution more of the original architectural details will be able to be retained.

As the existing facade is bolted directly onto the steel frame of the building with minimal insulation, the internal space suffers from poor thermal performance in both winter and summer. The EOC team has identified that, instead of replacing the unique, white galvanised steel facade, its performance can be improved by simply moving it out by around 200mm with newly designed bracketry. The newly created void can then be insulated and fire protected.

At the same time, the 8.5mm thick original single glazed windows will also be replaced by new insulated glass units. As the existing glass is monolithic, toughened it is then the intention to reuse it internally for new partition walls.

This retrofit first approach will not only bring the building up to current standards, but greatly improve the sustainability of the refurbishment.