The Maria von Linden grammar school in Calw was fully renovated while the school remained in operation. In addition to the renewal of building services installations, thermal insulation, new windows and interior surfaces, the building envelope was also renovated. The architects at 21-arch opted for sustainable öko skin slats in terracotta. The cheerful shade of red lends the outer shell a vibrant look and evokes the atmosphere of old brick houses. Photos: Ditz Fejer