Energy efficiency retrofit. A comparative analysis of different strategies to optimise the energy efficiency of a building

The building sector is one of the key consumers of energy in Europe; consequently, European Union has enacted several directives dealing, directly and indirectly, with energy efficiency in building aiming to reduce the buildings energy use. Hence, retrofitting of the current built environment offers significant opportunities to decrease energy consumption and greenhouse gas emissions. Aim of this paper is to investigate the potential of energy-efficient retrofitting strategies of existing buildings. The approach is structured according to three main phases: (a) the building performance assessment at the state-of-art; (b) the analysis of results to identify the possible retrofitting strategies; (c) the investigation of potential energy saving measures. The case study is an accommodation of the University of Milan, located in a residential area of Milan (Northern Italian city). The building behaviour is analysed to detect the most dispersant structures and the plants systems with the lowest efficiency. Afterwards, several simulations are implemented on Edilcima ® to estimate in which extent different typologies of retrofitting contribute to the whole energy performance. The global performance index in reference to non-renewable sources, i.e. the total energy consumed by the air-conditioned zones per square meter of surface every year, is used as indicator to compare the outcomes. The results show that, with reference to the existing conditions of the case study, by coupling the insulation of the most dispersing surfaces, the replacement of less efficient plants and the installation of a rooftop photovoltaic system, it is possible to decrease the whole primary energy consumption approximately by 30.52%.