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.

Many recent major studies, including the IPCC’s Fourth Assessment Report, have attested that energy efficiency is humanity’s prime option to combat climate change in the short- to mid-term. The potential to avoid CO2 emissions cost-effectively has been reported to be significant through efficiency policies. However, the review of global research findings on the quantification of cost-effectiveness of opportunities through improved efficiency has highlighted that there is a major shortcoming in the vast majority of such calculations.