Evaluation of Energy Efficiency Measures and Use of the Photovoltaic Thermal System with Insulation for a Historical Four-Story Residential Building in Italy

Today’s increasing energy prices underscore the urgency and advantages of accelerating the development of cheaper and cleaner sources of energy. The natural gas crisis in Europe caused by Russia’s invasion of Ukraine has affected the energy market and fuel prices much more than expected [1]. The current situation requires a significant change in considering energy resource consumption. The household and business buildings and their construction sectors combined account for almost one third of total global final energy consumption and around 15% of direct CO2 emissions among all energy-consuming sectors [2]. Buildings are responsible for around 40% of European Union energy consumption [3]; therefore, reducing energy consumption and the carbon footprint must be considered as soon as possible [4]. To reach these aims, many regulations, strategies, and directives have been deployed to lead the reduction of energy consumption by promoting energy efficiency actions [5]. Currently, energy systems planning and models are concentrated on analyzing the various renewable energy and energy efficiency measures implementations. The main aim is to comprehend the amount of main and primary energy resources that can be saved and their beneficial consequences on the environment [6]. Many studies have been conducted in different regions and energy sectors across the world. Among all of them, building raised the interest of many researchers [7]. Recent trends show that due to rapid urbanization around the world, above 70% of the total population will be living in cities by 2050. It is obvious that cities are featured by a large number of buildings which are undeniably responsible for a huge amount of energy consumption and carbon emissions [8]. Within European Union, Italy is the third energy-consuming country after Germany and France. Thus, different authors focus on the development of energy consumption models applied to the Italian building stock also in consideration of the high level of energy dependence of the country, especially natural gas which is used for heating and domestic hot water [9]. According to the most recent report published by the European Climate Foundation and the European Alliance to Save Energy (EU-ASE), electrifying and renovating Europe’s residential buildings can cut gas imports and generate massive benefits for the economy. The equivalent of 25% (or 1.45 EJ) of the EU’s current fossil gas imports from Russia (~5.5 EJ in 2020) can be saved by 2030 by renovating and electrifying Europe’s residential buildings. As a result, Europe could cut its annual spending on gas imports by €15 billion in 2030 and €43 billion in 2050 and therefore help increase Europe’s energy security [10]. As shown in Fig. 1.1, the Italian residential sector consumes the most natural gas during the last 15 years [11].