Currently, several research projects investigate Additive Manufacturing (AM) technology as a possible construction method for future buildings. AM methods have some advantages over other production processes, such as great freedom of form, shape complexity, scale, and material use. These characteristics are relevant for façade applications, which demand the integration of several functions. Given the established capacity of AM to generate complex geometries, most existing research focuses on mechanical material properties and mainly in relation to the load-bearing capacity and the construction system. The integration of additional aspects is often achieved with post processing and the use of multiple materials. Research is needed to investigate properties for insulation, thermal storage, and energy harvesting, combined in one component and one production technology. To this end. the research project "SPONG3D' aimed at developing a 3D-printed façade panel that integrates insulating properties with heat storage in a complex, mono-material geometry. This paper gives an overview of the panel development process, including aspects of material selection, printing process, structural properties, energy performance, and thermal heat storage. The development process was guided by experiments and simulations and resulted in the design and manufacturing of a full-scale façade element prototype using FDM printing with PETG. The project proved the possibility of the integration of functions in 3D-printed façades, but also highlighted the limitations and the need for further developments.