## 1 Introduction  
Recent earthquake events in Southern Europe (Italy [1, 2], Albania [3], Greece [4], Turkey [5], or Croatia [6]) revealed similar issues of the vulnerability of building stock [7] in all the aforementioned countries. Analysing only the recent earthquakes in Croatia, after the Zagreb earthquake, some 25,000 buildings were damaged, the majority of them in the city centre, while after the Petrinja earthquake, some 56,000 were damaged, mainly in rural areas. A total of 4621 buildings were rendered unusable due to damage [8]. The World Bank estimated the total financial costs of the damage from the Zagreb earthquake at EUR 11.3 billion and EUR 5.5 billion for the Petrinja earthquake [9, 10]. These devastating events resulted in the need to quickly take care of a large number of people, i.e., to find them temporary and/or permanent residence, as well as to return their usual lives to \"normal\" as quickly as possible (shops, hospitals, kindergartens, etc. ), not to mention establishing places of work for the people. Unfortunately, it turned out that the applied modular solutions were not adequate, because they mainly included conventional construction site containers in which it is impossible to live in the summer (overheating)but also in the winter (cold, excessive surface condensation, and mould growth), and they are huge consumers of energy. At the same time, such modular constructions are unsafe for life due to bad and overloaded installations (fires due to electrical installations) [11]. Emergency housing units, such as temporary buildings, are thought to be appropriate solutions to meet the needs of the earthquake-affected population for a medium period of time (approx. two years) during which damaged buildings can be rebuilt or repaired [12]. For this purpose, modular buildings have a wide variety of uses as both temporary (re-locatable) and permanent structures. Modules are produced in standard sizes and shapes, and can then be assembled on site into buildings with many repetitive units or can be assembled into more advanced architecture. The module must also be flexible to operate as a single and self-sufficient building or, exploitable as a part of cluster of several modules to form larger building. This paper will deal with the possibility to use module as a single self-sufficient building with the useful floor area less than 50 m\({}^{2}\). For the temporary buildings and stand-alone buildings with a useful floor area less than 50 m\({}^{2}\), the EPBD II Directive [13] states in Article 4 that Member States may decide not to set or apply the minimum energy performance requirements for several categories of buildings, among which temporary buildings with a time of use of two years or less are mentioned. This article was then transposed to Croatian legislation [14] as well as in Italian legislation [12], meaning that temporary buildings used in emergencies are not required to comply with minimum energy performance or emissions of the building. In the Italian case, this proved to be a significant setback, since after numerous seismic events that have struck Italy, the use of emergency housing units, as well as temporary schools, etc., has exceeded two years. In the case of the L'Aquila earthquake in 2009, some of the temporary structures are still used in 2022 [12]. In case of earthquakes that struck Croatia in 2020, it is now clear in mid-2022 that the temporary buildings erected will be in use for a substantially longer period than two years. In addition, people living in temporary housing in Croatia are receiving very high utility bills for electricity (used for heating and cooling), the fire safety is at risk, and there are issues with condensation of water vapour in their temporary units.