The construction industry stands as a primary energy consumer and a significant emitter of Greenhouse gases, making a substantial environmental impact. The industry's extensive material usage and inadequate building energy efficiency compound the detrimental environmental effects. Notably, the energy performance of buildings within the Italian built-stock registers particularly low figures. A closer examination of energy certifications issued in 2021 reveals that 34% of these certifications fall into the G class. This study explores the potential environmental advantages of using bio-based materials for building retrofitting. To achieve this, a comparative cradle-to-grave Life Cycle Assessment (LCA) will be conducted on a real case retrofit project. The LCA will compare two design scenarios: one utilizing bio-based materials and the other using conventional synthetic materials. Results indicate that material production has the greatest impact across most categories, but building energy use dominates global warming, abiotic depletion, and ozone depletion. Bio-based materials offer a potential environmental benefit, particularly for global warming potential where a 96% reduction is observed compared to conventional materials. This advantage is attributed to the biogenic carbon sequestration of bio-based materials.