Techno-economic analysis of energy retrofit in residential buildings in the urban context of Padua

In Europe, buildings are responsible for 40% of final energy consumption, 39% of this energy is related to space heating. The Energy Performance of Buildings Directive (EPBD) defines that 75% of buildings in Europe are classified as energy inefficient. These data highlight the importance of renovating the existing building stock to reduce the carbon footprint of the sector and the energy cost of users. However, high renovation costs make it essential to identify interventions that are both energy-efficient and economically sustainable. This work presents an energy and economic analysis of retrofit interventions on six case studies of residential buildings in Padova, selected based on real gas consumption data. The analysis is based on the modelling and validation of the selected buildings using the EnergyPlus software. The archetypes were defined according to the construction period and information about geometry from public archives. The proposed solutions were given following the architectural and historical constraints, if present, of each building. A deep retrofit was considered where limitations were not present, whereas standard retrofit solutions were investigated according to the constraints. As for the latter, the analysis ranges from the envelope to energy systems retrofit techniques. Thermal insulation solutions were compared, as well as heat pumps and photovoltaic integration. Furthermore, an economic evaluation was performed, accounting for the environmental impact. This was quantified considering the new European Emission Trading System 2 (ETS 2) carbon pricing. The results that were obtained show that in the case of deep retrofit, a reduction of primary energy linked to the heating system between 60% and 80% can be reached, also in the case of buildings with architectural constraints. The interventions analysed reported that a reduction of around 70% of CO₂ emissions was achieved in each case study, with a higher value, up to 84%, in the case where a PV system could be installed. Without carbon pricing instruments, the private financial optimum does not generally coincide with the energy and emission scenario targets required by a deep retrofit scenario.