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.

Circular economy (CE) as a new model of economic development promotes the maximum reuse/recycling of materials, goods and components in order to decrease waste generation to the largest possible extent. It aims to innovate the entire chain of production, consumption, distribution and recovery of materials and energy according to a cradle to cradle vision.

Cooperation between public and private sector has achieved a remarkable widespread, in the Italian context, over the last two decades. Nevertheless, the increasing difficulty in accessing the capital market and the rising cost of funding sources, both noticeable over the past few years, led to a slowdown of Public–Private Partnership (PPP) initiatives. Meanwhile, the community is expressing new needs to be satisfied, such as the conversion of brownfields, the recovery of housing stock dating back to former times, as well as the refurbishment of public offices or schools.