GEOTABS refers to the combination of a geothermal heat pump with thermally activated building systems, and is applied in low temperature heating and high temperature cooling of buildings. TABS is a radiant heating and cooling system and is beneficial in terms of thermal comfort and energy efficiency. When combined with a geothermal heat pump, it allows to make efficient use of low grade renewable energy sources. In this paper the benefits and opportunities of GEOTABS are explained. From current practice challenges are identified that prevent the system to be operated at an optimal efficiency and to be widely implemented. Key challenges are (1) to maintain thermal comfort when sudden and significant changes in heating or cooling loads appear, (2) to maintain the thermal balance of the ground, (3) to design and control the system optimally, and (4) to decrease investment, design and commissioning costs. In the hybridGEOTABS H2020 project, three solutions are proposed and developed to tackle these challenges: (1) to integrate GEOTABS with secondary emission and heating/cooling generation systems, (2) to develop a robust and adaptive model predictive control and a toolchain that allows to derive the model architecture and parameters semi-automatically, and (3) to develop a holistic and easy-to-use design procedure that allows optimal integration, sizing and controlling of GEOTABS and secondary systems while avoiding case-bycase simulation work. This integrated solution will allow a near-optimal design and energy-efficient operation of hybridGEOTABS buildings within the boundaries of good thermal comfort and economic feasibility.