High performance glass such as low-e coated or heat reflective glass offers better thermal performance, preventing undesired heat loss or gain during a building operation phase. However, these coatings may not be as effective in certain climate zones and create glare problems for adjacent buildings. A transparent composite façade system (TCFS) was newly configured to provide a sustainable alternative to a high performance glass wall in that the biofiber composite core acts as a shading device while the airspace between the polymer skins provides adequate insulation. A comparative life cycle assessment (LCA) method was selected as a sustainability measuring tool to compare the environmental impacts of a TCFS with a glass curtain wall system (GCWS). In this paper, the environmental performance of a façade system is characterized by the energy consumption and CO 2 emissions through all stages of the life cycle. Comparative LCA results show that the total life cycle energy of the TCFS is estimated to be 93% of that of the uncoated GCWS, and the total emissions of kg CO 2 equivalent for the TCFS is determined to be 89% of the uncoated GCWS. The use phase for both the TCFS and GCWS plays a dominant role in reducing environmental impacts while the impact associated with transportation and the end-of-life management is estimated to be insignificant in this study. The life cycle inventory data and analysis results provided in this paper are expected to assist designers with a better understanding of building material selection and system improvement from the whole life cycle perspectives.