Valorization of recycled waste in the development of sustainable composite materials for thermal insulation in buildings

Optimizing the energy performance of buildings while ensuring satisfactory thermal comfort represents a crucial challenge for both society and future regulatory guidelines. The aim is to design interior spaces that are pleasant to live in while minimizing energy consumption and reducing negative environmental impacts. In this respect, enhancing the building’s thermal barrier envelope is a key strategy. The present research proposes a novel approach to improving energy savings by examining an innovative, eco-friendly insulating material derived from recycled composites. The main objective of this work is to investigate the thermal, mechanical, and water absorption characteristics of these composites to evaluate their potential as building insulation materials. The composites are composed of a stable mixture of 80% cardboard and 20% date palm fibers, in which polystyrene is incorporated at 2%, 4%, and 6%. Thermal behavior was investigated through the hot disk method, which provides accurate data. A dedicated experimental setup was specifically designed to replicate moist environments and perform tests of capillary water uptake to assess moisture responsiveness. Compression tests on cylindrical specimens with radially oriented layers demonstrated satisfactory structural strength. The bulk mass density of these samples varies from 212.54 to 263.75 kg/m³, while their thermal conductivity varies between 0.085 and 0.104 W/m·K. This demonstrates insulation performance comparable to that of standard products. The highest capillary water uptake values lie between 217% to 297%, reflecting variability in moisture resistance. Compressive strengths ranged from 0.8 MPa to 3.3 MPa, indicating their potential application in structural elements. These results demonstrate that composites made from cardboard waste, date palm fibers, and used polystyrene can provide good thermal and mechanical performance, representing an economically and ecologically viable alternative to improving energy performance within construction applications.