Achieving sustainable glass facades requires a profound understanding of the temporal shifts in the long-term thermal performance of Insulating Glass Units (IGUs). The insulation effectiveness of IGUs is not static; any degradation directly impacts the carbon footprint of a building, necessitating its consideration from both the initial design phases and at the point of evaluating the existing fabric. This issue is exacerbated by evolving climate conditions and increasingly stringent demands on IGU performance, raising concerns about the predictive accuracy of standardized testing for effective service life. To address these challenges, understanding failure mechanisms— such as argon gas leakage and potential Low-Ecoating deterioration—is essential to extending IGU lifespan and optimizing energy efficiency. Failure in these components may result in increased thermal transmittance, accelerated energy losses, and a corresponding rise in greenhouse gas emissions, which will ultimately shorten the effective service life of IGUs and elevate both operational and embodied carbon values. Field-testing IGUs to evaluate performance degradation offers crucial insights, enabling a data-driven approach to model these shifts accurately over time. Such empirical data is foundational in constructing a dynamic facade model, capable of forecasting IGU-related carbon emissions across various lifecycle stages. Through dynamic modelling, we can establish a robust framework for managing IGU lifecycle phases strategically, from operational use to recycling, reuse, or repurposing. As the imperative to achieve net-zero buildings intensifies, identifying current trends and improvement areas in IGU design and lifecycle management becomes critical. By advancing product performance and refining lifecycle strategies, we enhance the role of glass as a cladding material of the future for high-performance, low-carbon building envelopes. This paper discusses the essential developments needed for the sustainable evolution of IGUs to underpin glass facades as a cornerstone in the pursuit of a net-zero built environment.