Abstract
<jats:title>Abstract</jats:title> <jats:p> The construction sector urgently needs to mitigate its significant environmental and economic impacts, particularly through more efficient waste management. This study addresses sustainability in construction by introducing a new waste management methodology focused on the early project design and bidding stages. Its main goal is to promote more sustainable cities by reducing waste-related environmental and economic impacts. The methodological proposal incorporates the waste loss factor into unit cost analysis (UCA) and combines it with Ábaco, an innovative web management platform that categorizes waste by composition and hazard. Furthermore, the new UCA formulation enables estimating project CO <jats:sub>2</jats:sub> emissions during these early stages through a life cycle assessment (LCA) using the One Click LCA tool. To validate the loss factor, 71 construction professionals were surveyed to determine its percentage of key materials, and its probability distribution was modeled using Crystal Ball (version 11.1.3.0.0) software. The results show that ceramics have the highest loss factor at 9%, while other significant materials range from 5% to 7%. The key contribution of this study is to provide project managers with a valuable tool and a solid basis for accurately estimating waste-related costs from the outset, designing more efficient waste management strategies, reducing environmental impacts throughout the life cycle, and promoting transparency and competitiveness in bidding processes by lowering overall project costs. In terms of industrial adoption, integrating this methodology enables companies to optimize profit margins and enhance competitiveness in bidding processes by replacing generic contingencies with probabilistic loss data, thereby reducing financial uncertainty, improving cost transparency, and supporting compliance with emerging sustainability and carbon disclosure requirements. </jats:p>