## 1 Introduction  
Building renovation plays a very important role in increasing operational efficiency and is also necessary to achieve carbon neutrality goals [1]. Current EU standards and regulations support this renewal trend. The second trend is the intensive introduction of renewable sources to supply buildings with energy or the obligation to install RES in newly built buildings. The main characteristics of fossil fuels used today are emissions of CO\({}_{2}\) and other pollutants, uneven distribution of sources, and expensive production costs [2]. On the other hand, renewable energy sources are uniformly available and environmentally friendly and can significantly compensate for the need for fossil fuels in the production of electricity and heat [2, 3]. The first step in increasing the efficiency of building operations is to reduce the need for energy [1, 2]. The need for energy depends mainly on the condition of the building constructions, i.e., perimeter walls, ceiling, windows and doors. Buildings in Slovakia built from 1950 to 1990 partially respected the minimum technical requirements valid at the time of construction [4]. This changed only after the legislation was harmonized with EU legislation. This fact is very well illustrated, for example, by the number of issued energy certificates, when the newest buildings are classified in classes A and B, while old buildings are often classified in classes E and worse [5, 6]. Recently, many studies have been carried out to address the synergistic effect of building renovation and the application of renewable resources, such as [5, 6, 7, 8, 9, 10]. In his study, [PERSON] [5] confirmed the importance of in-depth renovation of the building, which contributed to the reduction of the carbon footprint. Authors [PERSON] and [PERSON] [6] progressed from the evaluation of a single building to the creation of a group of buildings, which are considered as a single entity that achieved zero-energy building status in the summary evaluation. In general, the terms community, neighborhood, and district are used to denote a set of buildings in this sense [11]. The use of a specific term depends on the objectives of the study [12; 13] (reference) and also on the evaluated area, whether it is a part of the city, a separate unit, or a differently defined area [14; 15; 16; 17]. The definitions of energy community are also different. [PERSON] [18] defines a net zero community as an area where the need for energy has been reduced, and the consumption has been covered by RES. The US Department of Energy defines an energy community as an area where the annual amount of energy delivered is less than or equal to the amount of energy produced [19]. The European Union issued regulation 2010/31/EU--Energy Performance of Buildings Directive, which defines the term nearly zero energy district. This guideline was adapted, for example, by [PERSON] et al. [20] in their study. The update of this directive from 2018 established the objectives of the EU policy and set the goal of achieving highly efficient and decarbonized buildings by 2050 [21; 22]. A very important factor that affects the possible development of energy communities is primarily the geographical location, which is related to climatic conditions. The outside temperature and humidity have an effect on the heating, ventilation, or air conditioning of the interior spaces. The very location, orientation, and arrangement of buildings have an impact on the passive solar gains of the building, which directly reduce the need for heat for heating [16; 22; 23]. The orientation and arrangement of buildings are closely related to the possibility of installing PV. Several studies report the use of PV as the main means of achieving an energy-self-sufficient community [24]. Many of the very important studies carried out [12; 20; 21; 22] point to the possible coverage of heat consumption up to 70% by photovoltaic panels. If PV panels are combined with solar thermal collectors, it is possible to cover up to 90% of heat consumption.