## Modeling the Evolution of Construction Solutions in Residential Buildings' Thermal Comfort  
[PERSON] 1,*(c), [PERSON] 2(c) and [PERSON] 3  
Footnote 1: [[https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci)]([https://www.mdpi.com/journal/applsci](https://www.mdpi.com/journal/applsci))  
Footnote 2: [[https://www.mdpi.com/journals/article/pdf/10.3390/appl10](https://www.mdpi.com/journals/article/pdf/10.3390/appl10)]([https://www.mdpi.com/journals/article/pdf/10.3390/appl10](https://www.mdpi.com/journals/article/pdf/10.3390/appl10)). The EU buildings' policy framework has been evolving since the beginning of the 1990s, when a wide range of measures was put into motion to actively improve buildings' energy performance. Currently, the Energy Performance of Buildings Directive (EPBD) (Directive 2018/844/EU) [7] alongside the Energy Efficiency Directive (Directive 2018/2002/EU), are the most important European regulations on the buildings sector. Despite the current regulatory framework, most of the European existing buildings (about 75% of which are residential [4]) were built before the first thermal regulations and the percentage of new constructions (after 2000) is quite small [8]. The thermal properties of the built stock are assured by the heat transfer coefficients (_U-values_) of the corresponding constructive elements, which differ considerably across EU countries [9]. Over the years, the values have decreased as a result of consecutive thermal performance improvement policies. Due to the harsh winter weather conditions, Northern and Central European countries have a long tradition of incorporating insulating materials in construction, explaining the high thermal resistance of construction elements. On the other hand, the mild weather of Mediterranean countries led to the thermal quality of buildings being neglected, which is verified by higher _U-values_[10]. Portugal was chosen as a case study due to the high levels of energy poverty and the recognized lack of thermal quality in buildings [11]. More than two thirds of the existing Portuguese residential buildings (67.7%) were built before 1990, when the first Portuguese buildings thermal performance legislation (RCCTE-Decree-Law 40/90 [12]) was published [13]. Portugal, as other European countries, is characterized by an aged residential building stock with poor thermal characteristics, low penetration of space conditioning systems alongside with the low efficiency of the existing ones, and highest levels of energy poverty (according to the European Energy Poverty Observatory, more than 20% of the population is not able to adequately warm their homes) [14]. Regarding construction, Portugal followed the trend of the remaining European countries and has been improving the thermal characteristics of the main constructive elements (Figure 2). The greatest reductions in _U-values_ coincide with the publication of buildings' thermal performance regulations summarized in Table 1 of the Appendix. However, despite the comprehensive regulatory framework and the milder climate situation, heating energy consumption needs in Portugal are relatively high, reflecting the poor thermal performance of buildings [15]. The lack of insulation materials in construction as well as the scarcity of adequate heating systems (in 2011, the majority of residential buildings were either  
Figure 1: Final energy consumption per sector, European Union (EU)-28 [6]. heated by inefficient mobile heating devices or by open wood fireplaces [16] and in 2015, only 15.7% of the dwellings had air-conditioning systems [17]) contributes seriously to the country's relatively high heating and cooling needs. Previous authors have studied the Portuguese building stock quality but with other purposes. For instance, the study of [PERSON] et al. [18] sought to quantify and map energy poverty in Portugal and [PERSON] and [PERSON] [19] aimed at determining the space heating deficit across the country.