Circular building practices: An analysis of environmental impacts, challenges, and opportunities

The construction sector is one of the largest contributors to global greenhouse gas emissions, resource consumption, and waste generation. In response to these environmental challenges, this research explores the integration of Life Cycle Assessment (LCA) and Circular Economy (CE) principles to promote more sustainable and circular construction practices, with a particular focus on building materials and modular housing systems in South Asian countries, especially Pakistan. The primary objectives of this work were to: (1) review the state of the art in LCA and Circular Building Design (CBD) integration in South Asia; (2) experimentally verify optimal compositions for earth-based printable construction materials; (3) develop a combined CE-LCA framework for assessing the environmental and circular performance of conventional, commercial, and 3D-printed building blocks; (4) conduct a cradle-to-grave LCA of modular house wall panels using primary data and sensitivity analysis; and (5) identify barriers to Circular Building Practices (CBP) adoption in South Asia and propose an evidence-based implementation framework. The study conducted the first cradle-to-grave LCA of a modular house wall assembly in Pakistan, providing a detailed comparison between imported and locally sourced materials. Additionally, developed a CE-LCA model that evaluated building blocks using the Material Circularity Indicator (MCI) and Circularity Indicator (CI), highlighting the important circularity advantages of 3D-printed bio-based blocks over conventional concrete. The 3D-printed organic bio-based block, with its high MCI and CI values (MCI: 0.87, CI: 0.62), proves to be the most circular, while conventional concrete blocks remain the least circular (MCI: 0.48, CI: 0.24) due to their reliance on virgin materials and energy-intensive production processes The research highlights the importance of material selection, processing efficiency, and transportation logistics in determining the overall sustainability of construction materials. Experimental testing demonstrated the viability of earth-based printable materials incorporating natural fibers, offering locally sourced, low-impact alternatives for additive manufacturing in construction. Furthermore, a comprehensive survey of professional architects identified critical barriers to CBP in Pakistan, India, and Bangladesh, and an empirical framework was proposed to facilitate broader adoption of circular practices. This work contributes to the continually expanding amount of research on sustainable construction by providing practical methodologies for integrating LCA and CE, developing new circular materials, and informing policy and industry strategies. It lays a foundation for future research and practice aimed at achieving a more reformative and environmentally responsible built environment in emerging economies.