Thermal insulation materials based on agricultural residual wheat straw and corn husk biomass, for application in sustainable buildings

The high energy consumption in buildings is a major contributor to climate change and atmospheric pollution in south cities of Chile. In this context, insulation materials are a key factor to reduce the energy demand during the operational stage of a building. These materials are however commonly fabricated from petrochemicals with high energy consumption, causing significant detrimental effects on the environment during the production and discarding stage. Due these reasons, insulation materials based on natural fibers waste appear as an excellent alternative, due to abundant availability in south regions of Chile, potential low cost, low energy consumption during the production stage and high bio-degradation rate at the end of life. In this research, block type insulation based on wheat straw and corn husk residual fibers were developed. Taguchi method was applied to investigate the effect on thermal conductivity and density of four control factors in three levels, namely fiber length, boiling time; NaOH concentration and blending time; in a L-9 orthogonal array. Furthermore, flexural and compressive stress were determined and compared with expanded polystyrene block insulation. The results show thermal conductivity values were between 0.046 and 0.047 W/mK. In addition, flexural stress results were good compared to those of the standard expanded polystyrene type IX. Finally, optimum conditions of the process were determined to obtain a final block, which was morphologically analyzed using scanning electron microscopy (SEM), while the thermal behavior was studied by thermogravimetric analysis (TGA).