Optimizing energy-efficient building renovation: Integrating double-skin façades with solar systems in the Mediterranean landscape

According to the European Environment Agency, 85–95 % of today's buildings will still be standing in 2050. As a result, there is an urgent need to renovate existing buildings to reduce energy consumption and improve their energy performance. The use of double-skin façades (DSFs) integrated with active solar systems is a promising solution for energy-efficient retrofitting of buildings in Europe. A DSF with integrated PVs is a building envelope system consisting of two layers of materials separated by an air gap, with the outer layer incorporating solar panels to harness solar energy for electricity generation while providing additional thermal insulation and environmental control benefits. This paper explores the use of DSF with integrated solar active systems in Mediterranean countries, aiming to find the optimal solution for the energy-efficient renovation of the building stock. A parametric analysis is carried out, and the results show that the use of DSFs in multi-story existing buildings can be sustainable, as it saves energy without the need of adding insulation in the building. Specifically, results indicate that selecting a DSF with a depth of less than 7.0 m yields a reduction in heating demands ranging from −5.49 % to −0.82 %. Conversely, when contemplating cooling loads, a substantial DSF configuration exceeding 6.0 m in depth is the preferred option, facilitating a reduction in cooling loads. Additionally, the depth of the air gap cavity significantly influences electricity production, with increased depth leading to enhanced electrical efficiency and higher electricity production, i.e. from approximately 18.6 kW for the smallest cavity depth to a peak of around 26.8 kW for the greatest depth. The findings of this study can contribute to the development of effective policies and strategies for sustainable building renovation in Mediterranean countries.