Reusing Thermal Insulation Materials: Reuse Potential and Durability Assessment of Stone Wool Insulation in Flat Roofs

In the building renovation industry, a growing volume of discarded insulation materials, such as stone wool insulation, prematurely finds its way to landfills or incinerators after building demolitions. However, these materials often did not reach their complete service life potential, and the reuse of insulation materials is usually not considered in current building practices. This study provides a comprehensive overview of the potential challenges associated with repurposing stone wool insulation from existing flat roofs. By means of detailed assessments via dismantling and performance evaluations of collected stone wool insulation boards up to 28 years old, this research reveals the unavoidable damages that occur upon dismantling yet emphasizes that this does not impede reuse. While density and thermal performance remain stable over time, water absorption and mechanical stability are affected. In total, 48% of all short-term tests revealed an increase in water absorption, possibly due to hydrophobic substance degradation. Mechanical performances of aged SW insulation from flat roofs depend on various factors, with 43% and 33% of compression and puncture resistance tests, respectively, not meeting current standards. Beyond a durability assessment, this study advocates for a multidisciplinary approach, uniting materials science, construction engineering, and sustainability insights, to creatively repurpose used insulation materials into future projects.