Design, strategies, and performance monitoring for nearly zero energy buildings (nZEB): optimization and economic/environmental analysis in energy districts context

• Case study of an Italian single-family house refurbished to become full electric. • Modeling and real data monitoring of the net-zero energy building (nZEB). • Photovoltaic systems and storage implementation for loads self-consumption. • Evaluation of the usefulness of the nZEB inclusion in a positive energy district. • Environmental and economic analysis of the nZEB and the district. The final aim of this research work is to implement a re-qualification strategy for a district in order to create a sustainable urban area characterized by a complex of fully electric buildings powered by photovoltaic (PV) systems. This objective can be achieved by refurbishing buildings to create nearly zero-energy buildings (nZEBs). The nZEB concept is defined in the Energy Performance of Buildings Directive (EPBD), which has been revised several times by the EU to meet increasingly ambitious energy and climate targets. Including nZEBs in energy communities and smart districts is significant, since this type of building offers greater flexibility than standard buildings. This paper examines a real building located in southern Italy to analyse the specific actions adopted and the relative costs. To evaluate the energy performance of the building in real conditions, annual data monitored over the course of one year was examined, focusing particularly on the energy taken from the grid and sold to the market, the building loads, the self-consumption, the electricity produced by the PV panels and the electricity stored by the batteries. These data were used to define new energy- and economy-based indicators alongside traditional energy metrics in European regulations to accurately assess building performance. A hypothetical Positive Energy District (PED) scenario was studied to assess the effectiveness of this approach in an urban context. The environmental benefits and economic analysis show that the third scenario (larger PV installations and storage) is the most effective and sustainable, even if the initial investment costs are higher. By studying the real-world behaviour of the nZEB, it is possible to hypothesize the sizes of the PV system and storage under different boundary conditions, and to identify smart management strategies that can also be adopted when the building is included in an energy district scenario.