Renewable energy sources such as wind and solar require flexible adjustment of energy demand and shifting peak loads to periods of high generation. The Energy Systems Working Group researches innovative energy concepts, especially for existing buildings. The current focus is on TABS – Thermally Activated Building Systems, in particular using mass timber as a renewable building material. These TABS turn buildings into thermal energy storage, reduce the need for grid expansion, and promote the use of renewable energy. Multifunctional building systems combine building components and building services into a single system, saving resources and adding new functions. The Energy Systems Working Group develops these systems in collaboration with the Building Envelopes and Building Systems Working Group.