Additive manufacturing (AM) technology is currently being investigated as possible construction method for future buildings. AM methods have advantages over other production processes, such as great freedom of form, shape complexity, scale and material use. Because the freedom in geometric complexity applies also to the inner part of the products manufactured with additive processes, it is possible to customize inner geometries to integrate multi-functionalities. Products with multiple functions integrated are interesting for the building industry not only for the multi-functionality but also for the potentials of 3d printing these components in large scale.
Complexity in form and function is observed in the façade which is one of the most challenging parts of a building. Thus, an increasing interest in the application of advanced building envelope solutions can be seen both in research activities and in industrial developments.
Given the potential of 3d printing technology to generate complex geometries and include multiple functionalities, there are ongoing developments towards new or improved materials, production technologies and function integration. However, the focus of most research is directed towards the mechanical properties of materials and their use as part of load-bearing and construction systems. The integration of additional aspects is often achieved with post processing and the use of multiple materials. There is an important need for research into the limits of the performances specially for thermal insulation and building physics that can be combined in one component and one production technology. Moreover, there is need for additional investigation in the maximum printable size of façade components and on the challenges and the potentials to 3d print large-scale components.
To this end, the research project SPONG3D aims to develop a 3D-printed façade panel that integrates insulating properties with heat storage in a complex, mono-material geometry. The present paper gives an overview of the development process that took into consideration different aspects that the façade module needs to address and the challenges for the printing process, such as material use, printing time and scale. Those considerations and the thermal performance requirements drove the design iterations and tests and determined decisions related to the geometry and the printing technology selection. The interaction of these aspects resulted in the design and manufacturing of a prototype, which proves the potential of functions integration in such a façade, but also highlights the limitations and the need for further developments. The latest prototypes consist of 2 items. One working prototype (size: 660 mm(height)×200mm(width)×100 mm(thickness)) in which the water circulation is being tested. One prototype for demonstration (size:750 mm(height)×500mm (width)×360 mm(thickness)). At the same time, simulations were run to understand the thermal effects of the system on indoor spaces in different climates. With focus on the 3D printing process, the paper will present and discuss the results of each phase; as well as the design iteration that led to the current prototypes. Moreover, the paper will critically reflect on the challenges encountered during the research and will discuss the current limits of the work.
The research was conducted during 12 months of interdisciplinary teamwork, involving researchers from the façade discipline, thermal engineering and building physics, structural design, digital design and production.

Currently, several research projects investigate Additive Manufacturing (AM) technology as 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. The present 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 functions integration in 3D-printed façades, but also highlighted the limitations and the need for further developments.

Thermal mass is usually positively associated with energy efficiency and thermal comfort in buildings. However, the slow response of heavyweight constructions is not beneficial at all times, as these dynamic effects may actually also increase heating and cooling energy demand during intermittent operation or can cause unwanted discomfort. This study investigates the potential of energy simulations to support the exploration-driven development of two innovative responsive building elements: “Spong3D” and “Convective Concrete”. Both use fluid flow (Spong3D: water, Convective Concrete: air) inside the construction to reduce building energy demand by exploiting the use of natural energy sinks and sources in the ambient environment, aiming to make more intelligent use of thermal mass. During the development of these concepts, different simulation tools were used alongside experiments for e.g. materials selection, climate analysis, comfort prediction and risk assessment. By presenting the results from a series of simulation studies and by reflecting on their application, this paper shows how computational building performance analyses can play a useful role in ill-defined R&D processes.