Academicians and professionals in the architecture, engineering, and construction (AEC) field have expressed an increasing interest in sustainability and its application in the development of construction projects, especially with its deemed relationship with lean construction, for the purpose of improving efficiency in the construction processes. Practices framed under the lean philosophy show their potential in reducing environmental, economic, and social impacts during the construction phase, with an increase in the parameters of sustainability in the development of projects.

This study presents three cost-optimal calculations. The overall aim is to provide a deeper analysis and to provide additional guidance on how to properly implement the cost-optimality methodology in Member States. Without proper guidance and lessons from exemplary case studies using realistic input data (reflecting the likely future development), there is a risk that the cost-optimal methodology may be implemented at suboptimal levels.