A recent article published in Energy and Buildings presented a comprehensive analysis of thermal, acoustic, and environmental properties of prefabricated panels with three recycled insulations. Two of these were derived from polyethylene terephthalate (PET) and one from expanded sintered polystyrene (EPS) with graphite additive.
Background
The construction sector is responsible for about 39% of the total carbon dioxide emissions and 36% of the total energy use worldwide. Thus, the building sector is constantly trying to develop novel methods to achieve high performance with minimal consumption and emissions.
Material selection and optimization are crucial aspects of building design. They can simultaneously ensure low environmental impact and high performance, especially in thermal, acoustic, and sustainability terms. Consequently, prefabricated constructions are gaining popularity as they reduce construction time, energy consumption, and environmental pollution. Prefabricated construction can reduce waste generation by approximately 15%.
Numerous studies have investigated the structural properties of PET panels for their application in construction. However, only a few focused on thermo-acoustic properties, which are essential parameters to meet indoor wellness requirements. Thus, this study analyzed three recycled insulations for innovative prefabricated panels using a multiphysics, multiscale, and multiobjective approach combined with numerical analysis.
Methods
The researchers produced three multi-layered precast panels for large-scale testing, each comprising different insulation from EPS, PET (polyester fiber insulation from recycled plastic bottles), and EF_PET (PET with evolved fibers and different densities). Additionally, two types of small-scale samples were prepared to investigate the thermal (square samples of area 20×20 cm) and acoustic (cylindrical samples with a diameter of 10 cm) performance of the single layers constituting the precast composite.
For large-scale acoustic characterization, each panel was mounted on the outer wall of a test room building located at the University of Perugia and the airborne sound insulation of facade elements was measured in situ according to international standards. Alternatively, small-scale characterization of the insulation materials was performed to evaluate their acoustic insulation capability using the “two-load” transfer function method.
Large-scale thermal characterization was conducted through a thermo-fluximetric campaign using the Thermozig system. In addition, the small-scale thermal measurements were performed using a hot disk and the transient plane source (TPS) method to characterize each sample in terms of thermal conductivity, thermal diffusivity, and volumetric specific heat.
The panels were also assessed under different boundary conditions through a numerical analysis using the finite element method (FEM). Finally, a life cycle assessment (LCA) study was conducted on actual production data from an Italian mid-sized panel manufacturer to evaluate emissions throughout the panel’s production cycle, including the impact of each material. The calculations were performed using SimaPro 9.3.0.2 and the ecoinvent v.3.8 database.
Results and Discussion
The small-scale sound insulation test revealed better performance of EPS compared to the other two insulations, probably due to the material structure. Additionally, in the large-scale acoustic tests, the comparison of the facade sound insulation rating index of the test room with and without the panel exhibited promising results. The fabricated panels enhanced the structure’s sound insulation.
Small-scale thermal tests demonstrated good insulation properties of all insulation materials tested. The thermal transmittance results of large-scale testing matched the values determined from the small-scale thermal tests, proving EPS as the best-performing insulator, followed by EF_PET and PET. The large-scale testing allowed evaluation of the performance of multilayered precast panels when exposed to a real environment.
The numerical analysis using FEM further corroborated the experimental thermal and acoustic test results. It helped analyze the behavior of the fabricated panels in a validated numerical environment, incorporating experimental data. The LCA of panel production with PET was performed using a “cradle-to-gate” approach. It revealed that the concrete slab insulation in the panel contributed to maximum environmental impact because of its significant weight. However, replacing the concrete type could lower impacts and improve the performance of such a prefabricated system.
Conclusion
Overall, the proposed prefabricated panels in this study exhibited technically and environmentally promising results. Insulators derived from PET had good properties but were inferior to those of EPS. Thus, plastic-based insulations require improvement in their thermal and acoustic properties.
Novel materials like wood-wool-cement composite panels (WWCP) can be used for precast walls to improve sustainability and structural integrity. Furthermore, prefabricated timber structures are also a sustainable option for modular construction systems, emphasizing the use of renewable and recyclable resources.
Although this study focused on the Mediterranean climate of Perugia, the researchers propose that the methodology can be applied in different geographical contexts. Several promising recycled materials can be used in prefabricated panels to reduce environmental pollution and make efficient buildings.
Journal Reference
Cavagnoli, S., Fabiani, C., de Albuquerque Landi, F. F., & Pisello, A. L. (2024). Advancing sustainable construction through comprehensive analysis of thermal, acoustic, and environmental properties in prefabricated panels with recycled PET materials. Energy and Buildings, 312, 114218. https://doi.org/10.1016/j.enbuild.2024.114218, https://www.sciencedirect.com/science/article/pii/S037877882400334