As operational emissions decrease due to improved energy efficiency, reducing embodied carbon in buildings has become increasingly important. Life Cycle Assessment (LCA) is a widely used method to quantify these impacts. However, its implementation often remains data-intensive and time-consuming due to the need for detailed material inventories. This study analyzed 100 LCA reports submitted for G-SEED certification in South Korea to identify a core set of construction materials that accounts for the majority of total material mass. The findings revealed 12 key material categories—such as ready-mixed concrete, cement-based products, structural steel, wood, and interior finishes—that dominate embodied carbon contributions, with concrete alone comprising over 85% of the total mass. Based on these results, a material classification framework was developed according to functional role and carbon impact. By focusing on these high-impact materials, future LCA efforts can be significantly streamlined without compromising accuracy. This approach offers data-driven guidance for LCA practitioners, designers, and green building certification bodies aiming for efficient and reliable carbon assessments.