The building sector in the Netherlands contributes significantly to carbon emissions, with a substantial portion arising from embodied carbon in materials. Despite government efforts, the industry struggles to meet emission reduction targets. This thesis, examines the material selection process during the design phases of building projects to reduce carbon emissions. A qualitative approach, including a narrative literature review and semi-structured interviews, identified key barriers in decision-making, such as delayed decision-making, lack of data, and stakeholder misalignment. The study highlights the preliminary design phase as a critical “sweet spot” for impactful decisions and recommends early goal-setting, stakeholder collaboration, and continuous budget checks to enhance the sustainability of building projects.