Ceilings and roofs – depending on the building type and use – are responsible for around one quarter of CO2 emissions released during manufacture and construction. They therefore offer a huge lever for improving environmental footprints. Engineers at ZPF Ingenieure investigated the influence of material and construction on climate compatibility and cost based on current Swiss standards. This research and evaluation was prompted by the high sustainability requirements for the Hortus office building set by the developer Senn: the building is to amortise its grey energy in 30 years and be recycled in the circular economy.