Impact of connection to efficient district heating networks on the energy performance of residential buildings

In recent years, energy performance has been increasingly discussed in relation to the construction of a new building or the renovation of a house, as they represent a key indicator of energy efficiency and environmental impact. This thesis investigates the impact that the connection to efficient district heating systems can have on the energy and environmental performance of residential buildings and in particular on the non-renewable primary energy consumption, which determines the energy label of the building. Two case studies were analyzed: a single-family house located in Primiero (TN) and an apartment-block located in Vicenza (VI). The primary objective is to evaluate the energy performance of residential building before and after its connection to a district heating network defining the share of renewable and non-renewable energy based on the heat production mix. This scenario is compared with two alternative retrofit strategies: improving the building envelope and replacing the existing heating system with an electric heat pump. The results have been achieved using EdilClima software, allowing the calculation of Energy Performance Certificate (EPC), a mandatory document which certificates the energy performance of a building from the minimum (label G) to the maximum (label A4). The results show that the connection to an efficient district heating network can significantly reduce the non-renewable primary energy consumption to existing heating systems. However, the magnitude of these benefits strongly depends on the energy mix used in the district heating supply station and on the adopted primary energy factors. In buildings with poor envelope performance, the connection to district heating alone does not replace the benefits achievable through envelope retrofitting. The greatest reductions in overall energy consumption are obtained when building retrofit measures are combined with a high share of renewable sources in the heating supply. The thesis highlights the importance of the renewable energy sources into energy system, demonstrating that the decarbonization of energy supply plays an important role in improving the overall energy performance of buildings. Moreover, the study concludes that combined strategies promoting both the development of low-carbon district heating networks and building envelope renovation are essential to maximize energy savings and emission reductions in the residential sector.