The new office building of the Federal Environment Agency (Umweltbundesamt, ⁠UBA⁠) was erected as a model project for sustainable building with very ambitious goals. In order to significantly reduce the consumption of fossil energy sources, the energy demand of the building to be constructed had to be as low as possible to allow sustainable operation. The prime prerequisite for minimizing the energy demand is for the building to have a form as compact as possible as well as a highly heatinsulated shell.