Perlite and some recycled materials are preferably used to provide thermal insulation and lightness in mortar. Cement is often used as a binder in such a composite, although it makes the composite heavier and impairs its insulation properties. In this study, recycled bottom ash (BA) and expanded perlite (EP) as the aggregate, and cement as the binder and the optimum solution were investigated by using Taguchi Method. Depending on the specimens prepared using orthogonal array L9, the values of compressive strength, flexural strength, flowability, dry unit weight, water absorption, capillarity coefficient, and thermal conductivity coefficient were calculated. In general, it was found that the cement dosage was the most effective parameter and the thermal conductivity coefficient increased in parallel with the increase in unit weight and strength.