The evolution of building energy retrofit via double-skin and responsive facades: A review

The building sector is - directly or indirectly - the first pillar for application of technologies aimed at reducing energy wastes. To achieve sustainable growth goals, worldwide, the building stock needs to be re-developed from the energy viewpoint. This study focuses the attention on the building envelope, since it is the primary subsystem through which energy losses occur between inside and outside environments, by reviewing and discussing the most recent and cutting-edge researches in matter of double-skin and responsive facades for the building retrofit. Each study is investigated by characterizing the technology, the location (i.e., the climatic conditions) and season of analysis, the building intended use and the main findings. The objective is identifying potentialities and recurrent benefits related to the discussed retrofit solutions - such as reduction of energy consumption and CO2equivalent emissions, exploitation of renewables, conceptual transformation of the building envelope - but also barriers and criticalities - such as overheating risk, lower efficiency of transparent photovoltaics compared to traditional ones, high cost of responsive elements - which have to be addressed and solved in the future. In this vein, a comprehensive snapshot of the evolution of building envelope retrofit solutions is provided with original insights into current and future trends with a view to low- (or zero-) energy buildings. Despite the critical aspects and barriers to overcome, the potential advantages make most of the addressed technologies an important tool to achieve the sustainable renovation of the existing building stock, and therefore their potentialities must be deeply investigated and understood.