Cradle to Cradle certification, a strict assessment of the environmental qualities of materials used in green buildings, is a controversial provision in LEED V4. Those seeking LEED certification will get credits for Materials & Resources for disclosing and optimizing where building materials are sourced and purchased. The essence of Cradle to Cradle is the importance of a closed loop, that only materials and processes that can be reused endlessly should be included in product design. Buildings that have at least 20 Cradle to Cradle Certified products can earn points, or a project must use at least 25%, by cost, of the total value of permanently installed building products. Twenty-seven trade groups representing building materials industry companies oppose this provision, and are pushing Green Globes as a LEED alternative.