GlassECC is an EPD-based calculation tool for estimating the embodied carbon of insulating glass units (IGUs) using product-specific Environmental Product Declarations (EPDs). It is intended for early-stage design, comparative assessment, and transparent evaluation of façade glazing systems, enabling informed decision-making based on verifiable data. It operates exclusively on Environmental Product Declarations (EPDs) data in accordance with EN 15804 and ISO 14025. All embodied carbon values are derived directly from the manufacturer’s declared EPD’s without the use of generic datasets, industry averages or secondary databases. This tool has been developed in conjunction with the research paper presented at the Challenging Glass Conference 10.