The existing residential building stock accounts for a substantial portion of worldwide energy consumption and greenhouse emissions. Improvements to the thermal performance of existing buildings is a vital activity to mitigate climate change, and often has additional benefits in the form of improved comfort, health and well-being for occupants. Despite the extensive body of literature in this area, it remains a difficult task to assess the performance of retrofit packages in occupied residential buildings.

Accounting for over 70% of global CO2 emissions, cities are major contributors to climate change. Acknowledging this, urban climate change adaptation and mitigation plans are increasingly developed to make progress toward enhancing climate resilience. While there is consensus that focusing on both adaptation and mitigation is necessary for addressing climate change impacts, better understanding of their interactions is needed to efficiently maximize their potentials. This paper, first, provides a bibliographic analysis to map existing knowledge regarding adaptation-mitigation interactions.

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.