Addressing climate change through mitigation and adaptation strategies related to existing buildings represents a critical strategy for meeting global decarbonization goals set for 2050. In this context, recent studies have identified universities as strategic settings for implementing short-term actions and underscore their potential leadership role in climate change mitigation and adaptation efforts. The goal is to determine the scenario that leads to the most significant GHG reduction while representing resilience to extreme weather events and adaptability to climate change. This paper investigates the application of life cycle assessment in developing and evaluating energy retrofit scenarios that incorporate passive, active, renewables, and circularity strategies to enhance climate resilience and reduce GHG emissions in university buildings in temperate climates, such as Porto Alegre and Barcelona, in the context of extreme weather events. The project is structured into five stages: (1) Diagnosis and characterization of the building's situation; (2) Identification of legal and regulatory guidelines; (3) Formulation of renovation packages; (4) Assessment of renovation performance under climate change impacts; and (5) Sensitivity and uncertainty analysis. Additionally, the identification and analysis of best practices within the Catalan context, along with an in-depth study of thermo-energetic simulation techniques, were conducted to compose the method. This method features Life Cycle Assessment (LCA) integrated with thermo-energetic simulation and a carbon accounting framework that involves four stages: goal and scope definition, inventory analysis, impact assessment, and interpretation (according to ABNT NBR ISO 14040). The carbon accounting arises from the building's use, considering embodied emissions from maintenance, repair, replacement, refurbishment, demolition, transport, waste processing, and disposal resulting from retrofit actions, as well as operational emissions from the building's energy consumption during its use phase. In other words, it accounts for embodied and operational carbon in modules B2, B4, B5, B6, and C1 to C4 (end-of-life) according to EN 15978.