For its new international headquarters in Louvain-La-Neuve, IBA had drawn up a program of requirements with very challenging objectives for energy efficiency, comfort and flexibility. Crepain Binst Architecture explicitly chose an elegant and playful design. In the master plan IBA’s new headquarters is conceived as three different volumes, formally related and lying randomly in the landscape as boulders. The facade of the building looks like uncoiled bark. With its energetic sound open-closed ratio of 50-50% an ambitious e-level is guaranteed. The ambition is to achieve an excellent BREEAM score as well as a K36 and an E40 level.