Thermal Performance of Straw–EPSB Composites for Sustainable Building Insulation

The building sector significantly contributes to global energy consumption, largely due to heating, ventilation, and air conditioning systems. This study explores the development of eco-friendly straw-based composite insulation materials using waste expanded polystyrene (EPS) as a binder. In this approach, EPS waste is dissolved in a cellulose-based solvent to create a glue-like substance that is subsequently mixed with straw. The thermal properties of the resulting composites were evaluated using a transient hot-disk technique. Results indicate that increasing the straw fraction in the composite reduces both density and thermal conductivity, thereby enhancing its thermal insulation performance. In particular, the optimal formulation, designated as MSTE70 (30% binder, 70% straw), achieved a thermal conductivity of 0.0817 W/m.K, and density of 226.5 kg/m<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup>, and a specific heat capacity of 2028.72 J/kg.K. Furthermore, a dynamic TRNSYS simulation conducted on a small office building in Oujda, Morocco, indicated that integrating MSTE70 insulation reduced annual energy consumption by approximately 56%. These findings suggest that straw–EPS (MSTE) composites offer a promising sustainable alternative to conventional insulation materials, effectively balancing thermal efficiency and environmental sustainability.