Sustainable energy concepts for buildings feature highly energy-efficient systems for heating and cooling with a significantly reduced energy use, but also respect the occupants' requirements on interior thermal comfort. This work contributes to the evaluation and optimization of heating and cooling concepts for low-energy office buildings that use environmental energy and thermo-active building systems. The meta-analysis of the buildings and the achieved results in terms of energy efficiency and thermal comfort are based on longterm monitoring campaigns in 13 buildings over several years.