## 2 Materials and Methods  
The comparison proposed in this paper is based on sustainability assessment tools based on life cycle assessment (LCA) methods and environmental product declarations (EPDs) to compare construction solutions and materials. Two approaches were selected to  
Figure 2: Influence of carbon sequestration of bio-based materials over conventional materials emissions. Adapted from [13]. enable the use of multiple comparative methods for construction solutions that involve both conventional and bio-based materials, particularly those derived from fast-growing species. The first approach chosen is the open-access tool Building Emissions Accounting for Materials (BEAM) [16], developed by the organisation Builders for Climate Action to account for the carbon stored in bio-based materials. BEAM only considers the product stage of the building life cycle, i.e., the production phases from extraction to manufacturing, including transportation (modules A1-A3 on a life cycle assessment method). This explains the importance of this stage for carbon emissions that represent 65 to 85% of total life cycle emissions from building materials [16]. Other life cycle phases, such as transportation, construction, maintenance, and end-of-life scenarios, are not considered due to the assumptions that need to be made, which often lack accuracy, and can reduce assessment precision. This is a pragmatic choice to maintain the precision of results by avoiding including uncertain and variable factors. These activities depend on location, technology, and practices, introducing a high degree of variability. Estimating future activities, such as maintenance and end-of-life scenarios, involves predicting future practices, which is inherently uncertain. Additionally, accurate data for these activities might not be available or may be highly context-specific. The BEAM tool also considers carbon storage. The mass of biogenic material is calculated according to the EPD or LCA, and the mass of carbon on the biogenic material is based on the chemical composition from the Phyllis database [17]. It is important to note that only a determined list of materials, which are structure, enclosures, and partitions, is included in BEAM, as they represent most of the material mass and usually last more than 25 years. For this work, six exterior wall solutions were selected for comparison. Comparisons were made considering 100 m\({}^{2}\) of an external wall, and all simulations have the same thermal performance with a thermal resistance of 3 (m\({}^{2}\) K)/W, deemed sufficient for effective insulation. The materials for the solutions are chosen based on the items available in the tool database, considering both traditional and alternative options, as well as commonly used materials in the market. Concrete masonry and compressed earth blocks are chosen for the support wall, while extruded polystyrene (XPS), wood fibre, and hempcreate are chosen for insulation. Furthermore, a structured panel made of straw bale is also under consideration due to its innovative nature. The second approach involves applying the Methodology for Relative Assessment of the Sustainability of Construction Solutions (MARS-SC), a multicriteria tool developed by [PERSON] [18,19]. The methodology encompasses three dimensions: environmental, functional, and economical. Based on the performance of each dimension, the tool indicates the most sustainable options for specific requirements, allowing construction solutions to be chosen with the best balance between lower environmental impact, improved functional performance, and better economic feasibility. By highlighting gaps in available construction solutions for achieving specific sustainability goals, MARS-SC offers insights to guide research and development efforts towards creating new and innovative materials, technologies, and processes. Its utilization of life cycle assessment (LCA) data brings an evidence-based perspective to its analysis.