<p>This study investigates the optimization of thermal and structural performance in newly developed composite self-insulating concrete blocks intended for use in energy-efficient building applications. A comprehensive experimental program was conducted to assess the effects of various mix designs incorporating lightweight aggregates, recycled materials, and thermal insulating additives. Key performance indicators, including thermal conductivity, compressive strength, and density were systematically measured and evaluated. A design of experiments (DOE) methodology was employed to identify optimal mix proportions that achieve an effective balance between thermal insulation and mechanical integrity. The results demonstrate that specific material combinations can significantly enhance thermal conductivity while maintaining sufficient structural strength to meet conventional construction standards. Furthermore, an exponential strength development model was fitted to the experimental data using MATLAB, achieving a high correlation coefficient (R² = 0.93). This predictive model reliably estimates the compressive strength of the composite blocks up to 28 days and supports the advancement of sustainable, thermally efficient construction materials aligned with modern energy performance requirements.</p>