## 1 Introduction
### Study Context and Research Aims  
The presented study concentrated on the temperature course and the comfort perception of people above 45 years old who were inhabiting apartments in buildings constructed of prefabricated large-scale concrete plates, typical of the second half of the 20 th century in Poland. Dwellings in these buildings now constitute about 26% of the building stock in the country. They exhibit numerous similarities to residential buildings erected at that time in Eastern and Central Europe, including the design, building envelope, ownership structure, and even users' habits [39]. The findings of the presented research could be extrapolated to these buildings as well. By the time of their construction, the high thermal mass of concrete walls and floors and relatively low thermal insulation were sufficient protection against summer temperatures. During the years, these buildings underwent many thermal modernisations, aiming first of all at a reduction in energy demands during the heating season. This large building stock has been the focus of energy policy discussions in many post-communist countries of Eastern Europe [39]. Contemporary trends aim at the renewal of buildings of that type, preserving the rules of sustainable architecture, internal comfort, and the well-being of the occupants [40; 41; 42]. Nowadays, with growing external temperatures and solar irradiation, accumulative and insulating properties of the outer shell may not be enough to ensure comfortable internal conditions. The issue is all the more important because the population of residents of these buildings is growing older, which means that the occupants are more vulnerable and prone to the negative effects of overheating. The basis of this research was the monitoring of ten apartments (some of them of a repeatable architectural design) located in five- or twelve-storey buildings situated in two neighbouring districts in Lublin, a city in southeastern Poland. This region is recognised as having many arduous summer days with a large share of very hot and sulfry weather compared to the rest of the country [43]. The observations may then (to some extent) represent the most extreme conditions that can be expected in Poland. The dwellings were inhabited by middle-aged and elderly people (between 46 and 84 years of age). The main part of the monitoring took place between July and September 2023. During the study, the parameters, such as internal temperature, solar radiation intensity, window opening, and shading strategies, were measured and observed. External environment conditions were registered by meteorological posts belonging to the Department of Hydrology and Climatology at Maria Curie-Sklodowska University in Lublin (UMCS). Also, information about the inhabitants' behaviour and internal gains due to home appliances were collected via a questionnaire. The main aspect considered in this study was adaptive thermal comfort and its perception by the occupants in connection with the buildings' orientation, insolation, and protective measures against overheating. According to the literature, relatively little is known about the thermal environment in homes of the independent elderly in summer, and even less on whether these are perceived as comfortable (contrary to the thermal conditions in nursing homes) [32]. The novelty of the analyses lies in a practical evaluation of the internal conditions in buildings of a specific type that are inhabited by self-sufficient middle-aged and elderly people. This target group is more independent than, for example, residents in old age homes or hospital patients with moving difficulties. At the same time, they may experience more problems with adapting to worse climate conditions than younger people or typical families. These topics present a research gap in the literature and seem to be an interesting contribution to the field of thermal comfort evaluation in buildings.