Designing building wall systems is a multi-criteria problem characterised by a complex interplay of variables that drive long-term energy and environmental performance. Achieving holistic sustainability outcomes will require the application of life cycle thinking to the design and evaluation of building walling systems. However, the aspiration for minimising operational and embodied energy and mitigating the environmental impacts requires conflicting strategies. Therefore, this study proposes a comprehensive, integrated life cycle and energy simulation (ILES) methodology for analysing different walling systems of residential buildings in India and Australia. This method involves performing a process-based life cycle assessment to compute the environmental impacts of various walling materials, followed by energy modelling to evaluate the performance of these materials in the operational phase of buildings in combination with embodied energy analysis, which accounts for energy consumption during the material manufacturing phases. The results reveal that insulated cavity-clay masonry or concrete walls with extruded polystyrene are favourable Australian walling options, while metal cladding-based walling systems have significant environmental and energy burdens. For India, autoclave aerated block, fly ash bricks, and concrete block-based walling systems are recommended, while reinforced concrete and clay brick walls exhibit significant environmental and energy burdens. This study also advocates the consideration of supply chains in mitigating Scope 3 emissions from building walling systems in residential buildings.