When it comes to combating Climate Change, existing buildings offer immense, untapped potential, excluding them from the solution is simply not an option. Brutalist buildings, with their iconic, massive concrete forms, represent both a cultural legacy and a climate opportunity. Yet, the environmental discourse surrounding these structures often incorrectly emphasizes a key element: the substantial Carbon emissions already embedded (“spent”) in their concrete. This dissertation bridges that gap by introducing a high-resolution method to estimate these historical emissions, delivering powerful arguments for preservation and sustainable reuse. It challenges the often unsustainable practice of demolition and replacement, which discards the "sunk cost" of Embodied Carbon (EC) and generates significant additional emissions from new construction. A core contribution of this research lies in the development of a high-resolution methodology that integrates period-adjusted Embodied Carbon Coefficient (ECC) values with precise volumetric material quantification using Building Information Modeling (BIM). This comprehensive approach enables stakeholders to assign more accurate, data-driven metrics to a building’s EC. By providing this robust framework, the research empowers decision-makers to make strategic, informed choices regarding the preservation, retrofitting, and adaptive reuse of Carbon-intensive structures such as Brutalist buildings, turning them into assets in the fight against Climate Change. Using the Bromery Center for the Arts at the University of Massachusetts Amherst as a case study, the findings revealed a 46% higher EC estimate compared to standard calculations using current tools. This outcome emphasizes the critical role of higher-resolution data in EC assessments. Such granularity is essential when advocating for preservation, recalibrating expectations, and demonstrating that extending the lifespan of Brutalist buildings through thoughtful interventions is a more environmentally advantageous strategy.