The carbon emissions of future reinforced concrete structures need to be considered throughout their entire life cycle to meet CO2 reduction targets. This is critical for structures exposed to aggressive environments, such as chloride, due to the increased risk of reinforcement corrosion. Premature degradation caused by steel corrosion leads to significant repairs, increasing both the CO2 footprint and also the costs of the structure over its service life. This work proposes a design framework that integrates the laboratory performance concept consigned in the new Eurocode 2 and Sustainability Assessment. The framework’s applicability is demonstrated through a case study inspired by an existing structure. By employing a multi-criteria decision-making method, the proposed framework concurrently considers environmental impact and cost, facilitating the selection of the most balanced alternative in terms of environmental reduction objectives and budget constraints. The results show that appropriately selecting the Exposure Resistance Class leads to more cost-effective and environmentally friendly structures.