A Comparative Analysis of the International Regulation of Thermal Properties in Building Envelope

To achieve the goals of reducing building energy consumption, regulations are being designed to guarantee the appropriate energy performance of buildings. Both European and South American countries establish requirements of thermal properties of building envelope according to the climate zone, thus implying notable differences in climate classifications and technical requirements. This research provides a general view of advantages and limitations between the different state regulations of three South American countries (Argentina, Brazil, and Chile) and three European countries (Spain, Portugal, and France). A total of 792 simulations were conducted with Energy Plus by considering 12 different dwelling typologies in 66 climate zones. Building envelopes were adapted to the regulations of the various countries. Results showed tendencies of performance clearly different between the South American and the European countries, with the latter being those with the lowest energy demands. The cluster analysis of distributions of energy demand revealed that buildings located in similar climates but in different countries present very different energy performances. This research opens up the discussion on the development of more demanding policies related to thermal properties of buildings. Also, the analysis at a continental scale could reduce the differences between countries and guarantee a more sustainable life for the building stock.


Introduction
As a result of the oil crisis of the 1970s, concerns regarding the effects of climate change on the planet exponentially increased. High energy consumption, greenhouse gas emissions (GHG), and climate change nowadays constitute the main concerns of society. A greater requirement in the energy performance has been reflected in many sectors, including the building sector, as most existing buildings present bad energy behavior [1,2]. In quantified data, the building sector is responsible for 30% of the energy consumption worldwide [3], generating 40% of GHG emissions [4,5] In addition, the use of fossil sources to produce energy aggravates this situation-most of the energy consumed in 2018 was produced by fossil sources [6].
To reduce the progressive degradation generated by climate change, a total of 195 countries were committed to significantly reduce GHG emissions in the 2015 Paris Climate Conference, thus leading to ambitious objectives by 2050, both at continental [7] and state [8][9][10] scales. Most programs establish a demanding goal of reducing building energy consumption by more than 90% [8][9][10].

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Buildings and parts of buildings where energy is not used to regulate the internal temperature; • Temporary constructions for a use period of less than or equal to two years; • Independent buildings with a surface area less than 50 m 2 ; • Buildings for agricultural or industrial use that only need a small amount of energy for heating, warm water, or cooling; • Religious buildings; • Historical buildings.  As can be seen, the limitations of the thermophysical properties of the envelope depend on the climate zone of the building. The climate classification is regulated in the decree Arrêté du 26 octobre 2010 [37]. In this decree, climate is divided into three zones for winter (H1, H2, and H3) and four for summer (a, b, c, and d). A total of eight different climate zones are obtained from the combinations (see Figure 1).  As can be seen, the limitations of the thermophysical properties of the envelope depend on the climate zone of the building. The climate classification is regulated in the decree Arrê té du 26 octobre 2010 [37]. In this decree, climate is divided into three zones for winter (H1, H2, and H3) and four for summer (a, b, c, and d). A total of eight different climate zones are obtained from the combinations (see Figure 1).

Portugal.
In Portugal, the energy regulation of buildings is developed in the decree-law 118/2013 [38]. This decree-law was the transposition of the Directive 2010/31/UE in Portugal [39]. Recently, some articles of this regulation were modified in the decree-law 251/2015 [40]. Its application scope is as follows:
Greater intervention; in this aspect, the Portuguese regulation distinguishes two assumptions: (a) when the cost of intervention works in the building is greater than 25% of the total value of the building (not including the value of ground), and (b) when there is an extension of the building with a cost greater than 25% of the total value of the building.
Regarding the thermophysical properties of the envelope, the regulation Portaria 379-A/2015 establishes the limit values for envelope elements. Since 31 December 2015, the thermophysical properties of opaque and glazed elements of the envelope have been regulated with the limit values provided in Table I.05B of the regulation Portaria 379-A/2015 (see Table 4). Such limit values are established for the climate classification set up in Portugal. As can be seen, limit values are established according to the climate zone of the building. The climate classification of Portugal is included in the decree-law 80/2006 [41], where three climate zones are established by each type of season (see Figure 2): three in winter (I1, I2, and I3) and three in summer (V1, V2, and V3). Each city of Portugal belongs to a different summer and winter climate zone. Each index is classified according to both the heating degrees for the winter index and the external temperature in the summer index. The numeric indicator determines the severity of each climate, and those with the greatest value are the most severe. Like other regulations as in Spain, limit values for the thermophysical properties of buildings built in their territory are distinguished from those of buildings built in insular territories.

Spain
The regulation on energy efficiency of buildings in Spain started in 1979 through the royal decree 2429/79 (also known as NBE-CT-79 [42]). A climate classification of the country in five different regions was established in this decree, as well as the different limit values of thermal transmittance. This regulation was in force until 2006, when the royal decree 314/2006 came into force [43]. This last royal decree is divided into several standards, including the document of energy saving (also known as CTE-DB-HE). In both the version from 2006 and the subsequent reviews in 2013 and 2019, climates of the country are classified according to the climate severity in winter and summer, which is calculated depending on the heating and the cooling degree-days. The classification is carried out by distinguishing five zones for winter (A, B, C, D, and E) and four zones for summer (1, 2, 3, and 4); zones with a higher letter (e.g., E in winter) or a higher number (e.g., 4 in summer) are the most severe. A total of 12 different climate zones are obtained from the combinations of classifications of winter and summer (see Figure 3).

Spain
The regulation on energy efficiency of buildings in Spain started in 1979 through the royal decree 2429/79 (also known as NBE-CT-79 [42]). A climate classification of the country in five different regions was established in this decree, as well as the different limit values of thermal transmittance. This regulation was in force until 2006, when the royal decree 314/2006 came into force [43]. This last royal decree is divided into several standards, including the document of energy saving (also known as CTE-DB-HE). In both the version from 2006 and the subsequent reviews in 2013 and 2019, climates of the country are classified according to the climate severity in winter and summer, which is calculated depending on the heating and the cooling degree-days. The classification is carried out by distinguishing five zones for winter (A, B, C, D, and E) and four zones for summer (1, 2, 3, and 4); zones with a higher letter (e.g., E in winter) or a higher number (e.g., 4 in summer) are the most severe. A total of 12 different climate zones are obtained from the combinations of classifications of winter and summer (see Figure 3).   The CTE-DB-HE also establishes the limit values of thermal transmittance of envelope elements (see Table 5), which are assigned according to the winter climate zone of the building. These limitations are applied to new buildings and to interventions in existing buildings.

Chile
Chile was one of the first South American countries with a wide development on energy efficiency of buildings. The climate zone of Chile was approved in 1976 through the standard NCh 1079 [44]. This standard, reviewed in 2008, establishes the climate classification in nine different zones (see Figure 4). These climates have notable differences between them. The topography of Chile significantly influences the climate characteristics of the various regions (rainfalls, temperatures, solar radiation, etc.), as many research studies reflect [45][46][47][48]. Therefore, there are different microclimates as the altitude oscillates between 0-6000 mamsl [49]. Regarding the climate classification, distinctions are not made according to the climate severities of winter and summer (as in other countries) but according to the bioclimatic characteristics of each region. For this reason, the nomenclature of zones varies: An (the Andean and the upper pre-Andean border in the Chilean highlands), CI (the central valley between the NL zone and the pre-Andea of Andes), CL (coastal zone from Mount Aconcagua to the Bío-Bío valley), ND (region between the Costa and the Los Andes mountain ranges), NL (coastal zone between the border with Perú and the northern limit of La Ligua), NVT (northern region between the coastal zone and the Los Andes valley and between Pueblo Hundido and the valley of Aconcagua river), SE (region in the south from Chiloé to Tierra del Fuego), SI (region in the south from Bío-Bío to the Reloncaví inlet), and SL (coastal zone from Bío-Bío to Chiloé and Puerto Montt).
The NCh 1079 [44] also establishes the thermal requirements of the building envelope (see Table 6). As for the limitation of the thermophysical properties of windows, it is worth stressing that the limitation is associated with the maximum surface percentage allowed according to both the type of window and the climate zone of the building.   The NCh 1079 [44] also establishes the thermal requirements of the building envelope (see Table  6). As for the limitation of the thermophysical properties of windows, it is worth stressing that the limitation is associated with the maximum surface percentage allowed according to both the type of window and the climate zone of the building.

Argentina
Together with Chile, Argentina was one of the first South American countries with a regulatory development on energy efficiency of buildings. In this regard, one of the first standards marking the energy beginnings of the country was the standard IRAM 11603 in 1981 [50]. This standard made a bioclimatic classification of the country in six different zones (see Figure 5). The classification was made by naming zone I as the hottest zone and zone VI as the coldest. In a review conducted in 2012, a total of four subcategories were distinguished in zones I-IV according to the bioclimatic characteristics of each zone: a (zones with thermal amplitudes greater than 14 • C), b (zones with thermal amplitudes lower than 14 • C), c (zones of transition from zones with greater thermal amplitudes to others with lower thermal ranges), and d (coastal zones with low amplitudes throughout the year). In addition, the IRAM 11603 provides general guidelines related to the design of the envelope as well as the evaluation of favorable orientations and the compliance of minimum sunlight in buildings for dwelling purposes.
However, the subsequent development of IRAM 11605 [51] established more restrictive limitations on the thermal properties of opaque elements. The standard establishes limit values for the thermal transmittance of walls and ceilings according to three comfort levels: A (recommended), B (medium), and C (minimum). Also, distinctions are made in the limit values of thermal transmittance for the seasons of summer and winter (see Tables 7 and 8). In the distinction of thermal transmittance of winter, limit values are not assigned according to the climate zone but to the external temperature of the design established in the IRAM 11603 for different cities. For a certain building, the lowest values of both tables are assigned. These limit values were adopted as compulsory in the decree 1030/10 [52]. thermal amplitudes lower than 14 °C), c (zones of transition from zones with greater thermal amplitudes to others with lower thermal ranges), and d (coastal zones with low amplitudes throughout the year). In addition, the IRAM 11603 provides general guidelines related to the design of the envelope as well as the evaluation of favorable orientations and the compliance of minimum sunlight in buildings for dwelling purposes. However, the subsequent development of IRAM 11605 [51] established more restrictive limitations on the thermal properties of opaque elements. The standard establishes limit values for the thermal transmittance of walls and ceilings according to three comfort levels: A (recommended), B (medium), and C (minimum). Also, distinctions are made in the limit values of thermal transmittance for the seasons of summer and winter (see Tables 7 and 8). In the distinction of thermal transmittance of winter, limit values are not assigned according to the climate zone but to the external temperature of the design established in the IRAM 11603 for different cities. For a certain building, the lowest values of both tables are assigned. These limit values were adopted as compulsory in the decree 1030/10 [52].   Regarding the thermal characteristics of windows, the standard IRAM 11507-4 [53] establishes the limit values of thermal transmittance of windows for various categories (see Table 9). As for these categories, the decree 1030/10 [52] establishes that buildings up to 10 m height should have windows of category K5, and for buildings of greater size, the minimum category is K4. Table 9. Maximum values of thermal transmittance of summer of glazed elements of the building envelope (Argentinian regulation).

Brazil
In Brazil, the first regulatory development on the energy efficiency of buildings took place in 2005 through the NBR 15220 [54], in which the technical characteristics of social housing were established. These characteristics were assigned differently in the country through a climate classification in eight various zones (see Figure 6). Later, in 2008 and in the version reviewed in 2013, the standard NBR 15575 [55] established the thermal characteristics that buildings should have. In particular, limitations are established in the thermophysical properties of walls and roofs, distinguishing different limit values according to the climate zone (see Table 10).   The standard makes a distinction according to a subcategory similar to the Argentinian regulation: minimum, medium, and maximum. This subcategory is determined based on the minimum temperature differential in winter between the internal and the external temperature as well as on the maximum temperature differential in summer. The subcategory of the building leads to the variation of the thermal transmittance of the roof. Also, the absorptivity for walls and ceilings vary the limit values of thermal transmittance. This value of absorptivity is obtained from the values established by the NBR 15220 for wall surface materials. Finally, it is worth highlighting that the NBR 15575 does not establish limitations for the thermal transmittance of walls in the climate zones 7 and 8, and that there are not limitations in the thermal properties of windows. The standard makes a distinction according to a subcategory similar to the Argentinian regulation: minimum, medium, and maximum. This subcategory is determined based on the minimum temperature differential in winter between the internal and the external temperature as well as on the maximum temperature differential in summer. The subcategory of the building leads to the variation of the thermal transmittance of the roof. Also, the absorptivity for walls and ceilings vary the limit values of thermal transmittance. This value of absorptivity is obtained from the values established by the NBR 15220 for wall surface materials. Finally, it is worth highlighting that the NBR 15575 does not establish limitations for the thermal transmittance of walls in the climate zones 7 and 8, and that there are not limitations in the thermal properties of windows.

Methodology
The flowchart of the research procedure consisted of designing a set of building models and their evaluation of the useful energy demand obtained according to the thermal requirements of the envelope in each climatic zone (see Figure 7). For this purpose, models were simulated in the different climatic zones, and their envelopes were configured according to each regulation. Finally, a cluster analysis was carried out to assess the similarity between the climatic zones.
The flowchart of the research procedure consisted of designing a set of building models and their evaluation of the useful energy demand obtained according to the thermal requirements of the envelope in each climatic zone (see Figure 7). For this purpose, models were simulated in the different climatic zones, and their envelopes were configured according to each regulation. Finally, a cluster analysis was carried out to assess the similarity between the climatic zones.

Case Study
The results of this study were based on simulations carried out with Energy Plus. The energy demand was calculated by Energy Plus with dynamic hourly simulation. A total of 12 different building typologies were modeled for accurate knowledge (see Figure 8). Consequently, as 12 typologies were used, and there are 66 climate zones and regulations of the various countries (including the new regulation of France from 2023), a total of 792 different simulations were conducted. Models were designed to include different building typologies, from single-family dwellings to multi-family buildings. These models were based on other existing research studies on the subject matter [56][57][58][59]. Moreover, these designs were made to be similar to buildings of the countries analyzed. A limitation of two floors was established due to the variations presented by some regulations in the thermal properties according to the number of floors (e.g., Argentina in the thermal transmittance of windows). The percentage of glazed surface was 15% in all the opaque surfaces of the models.

Case Study
The results of this study were based on simulations carried out with Energy Plus. The energy demand was calculated by Energy Plus with dynamic hourly simulation. A total of 12 different building typologies were modeled for accurate knowledge (see Figure 8). Consequently, as 12 typologies were used, and there are 66 climate zones and regulations of the various countries (including the new regulation of France from 2023), a total of 792 different simulations were conducted. Models were designed to include different building typologies, from single-family dwellings to multi-family buildings. These models were based on other existing research studies on the subject matter [56][57][58][59]. Moreover, these designs were made to be similar to buildings of the countries analyzed. A limitation of two floors was established due to the variations presented by some regulations in the thermal properties according to the number of floors (e.g., Argentina in the thermal transmittance of windows). The percentage of glazed surface was 15% in all the opaque surfaces of the models. The thermal properties of each envelope elements were adapted according to the requirements established in the regulations described in Section 2. Table 11 indicates the standards used to establish the thermal properties of envelope elements. It is worth stressing that some countries do not establish limitations in some envelope elements. For example, values related to windows are not established in Brazil. For this case, a thermal transmittance of 5.7 (W·m − ²·K −1 ) was considered for the windows designed in all climate zones of Brazil, as it is representative of the type of window most used in the country [60]. As for countries that do not establish limit values of thermal transmittance of floors in contact with the air, and similar to what the Spanish regulation establishes, the limit value for roofs was the same for floors. Regarding France, which establishes limit values of thermal resistance, the limit value of thermal transmittance was obtained through the inverse of such values. Regarding the thermal transmittance of the floor in contact with the ground, it does not vary between the different climate zones, as only the Spanish regulation establishes some limit values. For this reason, a configuration of floor with a thermal resistance of 1.9 m²·K·W −1 was assigned to guarantee the compliance of the Spanish regulation in all climate zones. Window shading systems were not considered due to the differences in the typical window shading styles of each country (e.g., blinds in Spain or shutters in France). The thermal properties of each envelope elements were adapted according to the requirements established in the regulations described in Section 2. Table 11 indicates the standards used to establish the thermal properties of envelope elements. It is worth stressing that some countries do not establish limitations in some envelope elements. For example, values related to windows are not established in Brazil. For this case, a thermal transmittance of 5.7 (W·m −2 ·K −1 ) was considered for the windows designed in all climate zones of Brazil, as it is representative of the type of window most used in the country [60]. As for countries that do not establish limit values of thermal transmittance of floors in contact with the air, and similar to what the Spanish regulation establishes, the limit value for roofs was the same for floors. Regarding France, which establishes limit values of thermal resistance, the limit value of thermal transmittance was obtained through the inverse of such values. Regarding the thermal transmittance of the floor in contact with the ground, it does not vary between the different climate zones, as only the Spanish regulation establishes some limit values. For this reason, a configuration of floor with a thermal resistance of 1.9 m 2 ·K·W −1 was assigned to guarantee the compliance of the Spanish regulation in all climate zones. Window shading systems were not considered due to the differences in the typical window shading styles of each country (e.g., blinds in Spain or shutters in France). A general usage and load profile was used for all climate zones, thus making representative comparisons between the climate zones. Figure 9 shows the profiles used. The sensible load in weekends corresponding to 100% of occupancy was 2.15 W·m −2 , and the latent load was 1.36 W·m −2 . During the week, the sensible and the latent occupancy loads varied from 100% at night up to 0.54 W·m −2 and 0.34 W·m −2 (period between 08:00 to 15:00) and up to 1.08 W·m −2 and 0.68 W·m −2 (period between 16:00 to 23:00), respectively. The lighting and the equipment load varied throughout the day, being 100% (4.40 W·m −2 ) from 20:00-23:00. The number of air changes per hour was 0.69. All the models had a conventional natural gas boiler for heating with a coefficient of performance (COP) of 0.92 and a heat pump for cooling with an energy efficiency ratio (EER) of 2.00. Setpoint temperatures varied depending on the time of day (see Table 12). As the variations of latitude between South America and Europe cause a change in the winter and the summer months of the year, constant upper and lower limits were considered during all months of the year. Two aspects were therefore met: (i) the profile was valid both for South American and European countries, and it could also be used in climate regions with lower thermal oscillations throughout the year, such as some zones of Brazil; and (ii) the profile met those isolated cooling energy demands that could take place in winter seasons, such as in Spain (as some studies report) [61]. A general usage and load profile was used for all climate zones, thus making representative comparisons between the climate zones. Figure 9 shows the profiles used. The sensible load in weekends corresponding to 100% of occupancy was 2.15 W·m −2 , and the latent load was 1.36 W·m −2 . During the week, the sensible and the latent occupancy loads varied from 100% at night up to 0.54 W·m −2 and 0.34 W·m −2 (period between 08:00 to 15:00) and up to 1.08 W·m −2 and 0.68 W·m −2 (period between 16:00 to 23:00), respectively. The lighting and the equipment load varied throughout the day, being 100% (4.40 W·m −2 ) from 20:00-23:00. The number of air changes per hour was 0.69. All the models had a conventional natural gas boiler for heating with a coefficient of performance (COP) of 0.92 and a heat pump for cooling with an energy efficiency ratio (EER) of 2.00. Setpoint temperatures varied depending on the time of day (see Table 12). As the variations of latitude between South America and Europe cause a change in the winter and the summer months of the year, constant upper and lower limits were considered during all months of the year. Two aspects were therefore met: (i) the profile was valid both for South American and European countries, and it could also be used in climate regions with lower thermal oscillations throughout the year, such as some zones of Brazil; and (ii) the profile met those isolated cooling energy demands that could take place in winter seasons, such as in Spain (as some studies report) [61].

Climate Data and Cities Analyzed
Climate data were required for the energy analysis of the limit values of regulations to conduct simulations in Energy Plus. Such climate data were obtained with the METEONORM software. This tool is constituted by 8325 weather stations located all over the world and conducts interpolations between the different seasons to obtain hourly climate data in any location. The temperature period considered for generating EnergyPlus Weather (EPW) files was 2000-2009, and the period of radiation was 1991-2010.
Annex A includes a list of the cities considered for each climate zone. Cities were selected by using the different lists of cities associated with each climate zone indicated in the regulation of each country (see Appendix A). It is worth stressing two aspects: (i) as for the zone H3 of the French regulation, the city of Nîmes was used, as it is at an altitude lower than 800 m, and the values of the thermophysical properties were different than those of the other zones (if the city selected for the zone H3 had an altitude higher than 800 m, then the limit values were the same as for zone H2); and (ii) small overseas territories were not considered in the analysis (except Majorca in the case of Spain due to its proximity and its similarity with the near zones of the country).

Cluster Analysis
Finally, a comparative analysis between the results obtained among the climate zones presenting similarities was conducted. For this purpose, an independent cluster analysis was carried out for the climate zones of South America and Europe. A cluster analysis is a multivariant statistical technique that classifies a set of objects-similar objects are in the same conglomeration, and far objects are in different groups, giving as a result homogeneous k-groups [62]. The Ward method was used [63], which belongs to the agglomerative hierarchical methods, and the Euclidean distance was used as a distance measure [see Equation (1)]. The variables considered for each climate zone were the heating degrees-hours for base temperature of 20 and cooling degrees-hours for base temperature of 25.
where x i and x j are two individuals, and p is the number of variables considered.

Results and Discussion
Firstly, the mean percentage contribution of each type of energy demand (heating and cooling) was analyzed in the different zones. This step was made before analyzing each climate zone in detail, as the aim was for the discussion to be based on the total energy demand to simplify its interpretation. Figure 10 represents the percentage contributions of each type of energy demand. Results highlighted the heterogeneity of the climate zones and the thermophysical characteristics analyzed in the various countries. The greatest contribution of energy demand was due to heating in most climate zones-countries such as Chile and France as well as certain climate zones of Argentina (IIa, IIb, IIIa, IIIb, IVa, IVb, IVc, IVd, V, and VI), Brazil (Z1 and Z2), Spain (A3, C1, C2, C3, D1, D2, D3, and E1), and Portugal (I1V2, I1V3, I2V1, I2V2, I2V3, I3V1, I3V2, and I3V3) presented percentages greater than 75%. However, there were some zones where the contribution of the cooling energy demand was the most important type of energy demand (greater than 50%): (i) zones Ia and Ib in Argentina; (ii) zones between Z3 and Z8 in Brazil; (iii) zone I1V1 in Portugal; and (iv) zones A4, B3, and B4 in Spain. Among these zones, it is worth stressing the high contribution of cooling energy demand in zones of Brazil due to their location in latitude near the equator, which implies that the thermal oscillation between the different seasons is low and temperatures are warmer.
If these percentage values of cooling and heating are compared with the limit values regulated by the countries analyzed, three different tendencies are found: (i) Spain and Portugal establish fewer demanding requirements in the thermal transmittance of the building envelope elements located in zones with a greater cooling demand than in colder zones. As for Spain, the limit of thermal transmittance of walls goes from 1.25 and 1.0 W·m −2 ·K −1 ) in the climate zones of winter A and B, respectively, to 0.75 in the winter climate zone C; (ii) in Brazil, limit values of thermal transmittance are established between zones 3 and 6 and are similar to those of the coldest zones of the country (zones 1 and 2). Also, the regulation does not consider limit values for zones 7 and 8 (it is worth remembering that the case studies with the same limitations in zones 3 and 6 were analyzed in this study). This aspect reflects the little adaptation presented by these limit values according to the characteristics of each climate zone of Brazil with the same limitations in buildings located in warm and cold regions; and (iii) Argentina establishes a different criterion of regulation according to the severity in summer.
As previously seen, the main limitation is established by the mean design temperature in winter, as lower thermal transmittance values are usually established. However, as for roofs, the characteristics of summer may demand lower values. In this regard, both zones with a greater cooling energy demand (Ia and Ib) correspond to zones in which the lowest thermal transmittance value of roofs in summer is established (it would be 0.18 W·m −2 ·K −1 for a level A), and this value increases in those zones with a lower cooling energy demand (e.g., zones IIIa and IVb), thus reflecting the climate adaptation presented by the limit values of Argentina. After analyzing the percentage contribution of each case study in the various climate zones, the results of the total energy demand obtained by each case study were analyzed. It is worth remembering that the case studies presented different characteristics of orientation and design, which varied the total energy demand of each. The aim was to analyze the effect of the thermal limitations After analyzing the percentage contribution of each case study in the various climate zones, the results of the total energy demand obtained by each case study were analyzed. It is worth remembering that the case studies presented different characteristics of orientation and design, which varied the total energy demand of each. The aim was to analyze the effect of the thermal limitations on statal regulations with different designs of buildings.
As for France, there were two limit values: (i) limit values for buildings designed and built before 1 January 2023 (see Table 13); and (ii) limit values for buildings designed and built after 1 January 2023 (see Table 14). This variation of limit values only took place in the opaque envelope elements. Regarding the results obtained, the zone and the configuration presenting the lowest total energy demand was zone H2a, with a percentage reduction between 7.08 and 23.41%. The next two zones with a lower total energy demand were zone H3 (with a percentage reduction between 7.09 and 16.91%) and zone H1a (with a deviation percentage between 1.89 and 10.50%), thus showing the favorable conditions of summer classification of type a of the French regulation, as they were those with the lowest energy demand. Regarding the zones with a greater total energy demand, zones with a summer classification of type c (H1c and H2c) were those obtaining the highest total energy demand values.  The same tendency was found with the limit values for 2023-zones of type a of summer had the lowest values, and those of type c had the highest. The new limit values, however, influenced the total energy demand (see Figure 11). The percentage reduction was similar between the different zones, with average values between 5.34 and 6.50%. However, the values of percentage reduction presented a slight variation in zone H3. The values of percentage reduction were between 0.25 and 14.06%, whereas in the other zones, there was a greater concentration of such values of percentage reduction (between 7.47 and 3.88%). The reason could be the difference presented by the new limit values of the zone H3 in comparison with the other zones. As seen in Section 2, limit values of thermal resistance in 2023 for zones H3 at an altitude lower than 800 m are 2.2 (m 2 K)/W in walls. However, this limit value is the same as that used in current limit values, whereas in the other zones, there is an increase of 0.3 m 2 ·K·W −1 in the limit values of thermal resistance of walls. This difference could lead to changes in the tendency of percentage reduction of zone H3 with the other zones. Anyway, the improvement of new limit values will improve the energy performance of buildings, although this improvement could be insufficient if compared with the results obtained in other regulations. The results obtained in Portugal showed a better energy performance than that of France. In the climate zone where the lowest values were obtained (zone I2V1), the values of total energy demand oscillated between 44 and 469.1 kW·h·m − ² (see Table 15), whereas in the French zone H2a, they oscillated between 74.5 and 902.6 kW·h·m − ². Comparing the results obtained in the different Portuguese climate zones, zone I2V1 presented average percentage reductions between 10.02 and 57.85% in the total energy demand with respect to the other zones. It is worth stressing that zone I2V2 also presented a lower total energy demand. If the limit value is more restrictive as the winter classification increases (i.e., a more restrictive value in zone I3 than in zone I1), these results highlight how some of these values adjust to the climate characteristics of each region. However, two aspects reflecting a certain limitation of the Portuguese regulation were found: (i) the values of total energy demand in the coldest regions (I3) were higher than those of the other winter climate zones, thus showing that the limit values for such zones need to be reviewed to guarantee that there is not a considerable energy difference between the buildings of the different zones; and (ii) in regions with the same winter climate classification, summer climate zones of type 3 presented a greater energy demand than zones 1 and 2 (e.g., zone I2V3 in comparison with zones I2V1 and I2V2), thus also reflecting the need to establish new limitations in the thermophysical properties according to the summer climate zone, which could be related to the thermophysical properties of windows (e.g., solar factor).  The results obtained in Portugal showed a better energy performance than that of France. In the climate zone where the lowest values were obtained (zone I2V1), the values of total energy demand oscillated between 44 and 469.1 kW·h·m −2 (see Table 15), whereas in the French zone H2a, they oscillated between 74.5 and 902.6 kW·h·m −2 . Comparing the results obtained in the different Portuguese climate zones, zone I2V1 presented average percentage reductions between 10.02 and 57.85% in the total energy demand with respect to the other zones. It is worth stressing that zone I2V2 also presented a lower total energy demand. If the limit value is more restrictive as the winter classification increases (i.e., a more restrictive value in zone I3 than in zone I1), these results highlight how some of these values adjust to the climate characteristics of each region. However, two aspects reflecting a certain limitation of the Portuguese regulation were found: (i) the values of total energy demand in the coldest regions (I3) were higher than those of the other winter climate zones, thus showing that the limit values for such zones need to be reviewed to guarantee that there is not a considerable energy difference between the buildings of the different zones; and (ii) in regions with the same winter climate classification, summer climate zones of type 3 presented a greater energy demand than zones 1 and 2 (e.g., zone I2V3 in comparison with zones I2V1 and I2V2), thus also reflecting the need to establish new limitations in the thermophysical properties according to the summer climate zone, which could be related to the thermophysical properties of windows (e.g., solar factor). As for Spain, the results obtained were different and were characterized by a greater total energy demand despite the proximity and the possible similarity between the climate characteristics of Spain and Portugal. The lowest total energy demand was associated with zone C1, with a total energy demand oscillating between 66.9 and 677.6 kW·h·m −2 (see Table 16). The comparison with the other climate zones shows the huge difference with this climate zone, with a deviation percentage oscillating between 23 and 47.52%. The energy performance presented by the remaining zones was therefore higher than that of zone C1, thus showing a limitation of the limit values established by the CTE-DB-HE for the thermophysical properties of the envelope. The zones presenting a greater total energy demand were both cold (D2, D3, and E1) and warm (B3 and B4), and the latter associated the maximum values of energy demand in the 12 case studies (with values of total energy demand of up to 1306.4 kWh/m 2 ). Regarding the South American countries, three different behaviors were found, as Figure 10 shows: Brazil with a climate with a predominance of cooling energy demand, Argentina with a variable climate with a predominance of cooling or heating depending on the region, and Chile with a predominance of cold climates. In the case of the latter, Section 2 includes that NCh 1079 was the regulation establishing limit values for all climate zones. Despite this detailed regulation, the results obtained of total energy demand showed that there are notable differences between zones. The climate zone that presented the lowest total energy demand was the zone ND, with a percentage reduction between 29.07 and 79.95% (see Table 17). Thus, there was a huge deviation percentage between this zone and the others, as the remaining zones (except zone NL) had differences greater than 68%. The zone ND is characterized by establishing more restrictive values for the thermal transmittance of the envelope together with zones An and SE. Nevertheless, values of the NCh 1079 require review. Zones with more demanding limitations for the thermal transmittance should also be reviewed. The highest values of energy demand were obtained in zones An and SE, reaching maximum values of 1994.0 and 2246.5 kW·h·m −2 , respectively. There was an improvement in the values of the total energy demand in the climate zones of Argentina. The values of total energy demand presented a maximum of 1680.4 kW·h·m −2 (see Table 18), thus meaning a reduction of 25.2% with respect to the maximum value of Chile recorded in the zone SE. Among the zones and the configurations with the best energy performance, the zone IVa was the most efficient. Limitations of IRAM 11605 and IRAM 11507-4 caused the percentage reduction of the case studies in this zone to oscillate between 36.39 and 65.0%. As the limit values established for the zone IVa were the same as those of the remaining zones III and IV (because the external temperature of design was the same), the best energy performance of the case studies was due to the climate of zone IVa. This aspect therefore shows that the detailed climate classification established by the standard IRAM 11603 does not present the same level of detail in the limit values of IRAM 11605, thus causing differences in the energy demand between the various zones. This would also be a reason why, in some cases, the energy demand obtained was lower in the coldest zones (V and VI) than in zones III and IV. Finally, Brazil was the country associated with the greatest energy consumption. As Figure 10 shows, most climate zones are characterized by a greater cooling energy demand. Also, those zones with a greater percentage contribution of heating (Z1 and Z2) corresponded to zones with a low total energy demand (see Table 19). However, in zones with a greater contribution in the cooling energy demand, the values obtained were high. Values of total energy demand of 20183.4 and 34938.0 kW·h·m −2 were obtained in Z7 and Z8, respectively, mainly due to the limit values established by the standard NBR 15575. This standard establishes similar limit values for the different climate zones, being characterized by the values of thermal transmittance of walls between 3.7 and 2.5 W·m −2 ·K. Likewise, the Brazilian regulation does not establish limit values for the thermophysical properties of windows, thus leading to the high energy demand obtained in the case studies between zones Z3 and Z8. This aspect is in accordance with the low energy label, which is obtained by most social housing built in the country according to the NBR 15575 [64]. The values of the total energy demand between the regulation and the climate zones of the countries presented different tendencies (see Figure 12). The energy performance of the buildings built according to the Brazilian regulation is associated with a high energy impact in comparison with other countries. Consequently, new technical requirements need to be established in the thermal properties of the envelope with the objective of guaranteeing development and update of its efficient building stock with a low environmental impact. Regarding the other countries, Chile presents high values of total energy demand in some climate zones (e.g., SE and SI). There is also a notable difference in the tendencies of energy demand between the South American and the European countries analyzed; the latter were characterized by obtaining the lowest values of energy demand, whereas in the former, only some zones (e.g., ND in Chile and IVa in Argentina) obtained similar values. Despite the need to improve the European regulations, its wide development and update in recent years [23] has led to higher adjustment of thermal parameters of the envelope in different climate regions compared to the South American countries. This is shown, for example, in the case of Spain, with four modifications in the energy regulation of buildings since Finally, cluster analysis was conducted. Figure 13 shows the clustering of the climate zones of South America, and Figure 14 shows the clustering of the climate zones of Europe. A total of 13 clusters were obtained in South America, of which five were not grouped with any other climate zone, whereas 12 clusters were obtained in Europe with only two individual clusters. From the groups obtained based on the heating and the cooling degree-days, the variations presented by the case studies simulated in the same groups were compared. Figure 15 shows the box plots of the total Finally, cluster analysis was conducted. Figure 13 shows the clustering of the climate zones of South America, and Figure 14 shows the clustering of the climate zones of Europe. A total of 13 clusters were obtained in South America, of which five were not grouped with any other climate zone, whereas 12 clusters were obtained in Europe with only two individual clusters. From the groups obtained based on the heating and the cooling degree-days, the variations presented by the case studies simulated in the same groups were compared. Figure 15 shows the box plots of the total energy demand of the zones studied in South America and Figure 16 shows those of Europe.
Sustainability 2019, 11, x FOR PEER REVIEW 24 of 32 zone, whereas 12 clusters were obtained in Europe with only two individual clusters. From the groups obtained based on the heating and the cooling degree-days, the variations presented by the case studies simulated in the same groups were compared. Figure 15 shows the box plots of the total energy demand of the zones studied in South America and Figure 16 shows those of Europe.  As for the groups between different South American countries, there were differences in data distributions. In cluster J, the total energy demand in the zone IVa was lower than in zones CH-SE and CH-SI. Also, in some clusters grouping zones of the same country, such as cluster F, there were zone, whereas 12 clusters were obtained in Europe with only two individual clusters. From the groups obtained based on the heating and the cooling degree-days, the variations presented by the case studies simulated in the same groups were compared. Figure 15 shows the box plots of the total energy demand of the zones studied in South America and Figure 16 shows those of Europe.  As for the groups between different South American countries, there were differences in data distributions. In cluster J, the total energy demand in the zone IVa was lower than in zones CH-SE and CH-SI. Also, in some clusters grouping zones of the same country, such as cluster F, there were

Conclusions
This study analyzed the regulatory framework of the properties of the building envelope in countries of South America and Europe. Particularly, regulations on energy efficiency of buildings of Figure 16. Distribution of the total energy demand between the climate zones grouped in the cluster analysis of Europe.
As for the groups between different South American countries, there were differences in data distributions. In cluster J, the total energy demand in the zone IVa was lower than in zones CH-SE and CH-SI. Also, in some clusters grouping zones of the same country, such as cluster F, there were great differences in the results of total energy demand between zones. In Europe, there were similarities between the climate zones of Spain and Portugal, where the existing difference in the energy demand obtained in the case studies can be seen. The results showed that the Portuguese regulation generated a better energy performance than the Spanish regulation. These results reiterate the need for a general review of the thermal properties established in the regulations of the different countries and the use of new thermal variables, such as the periodic variables of UNE-EN ISO 13786 [65]. In this regard, the Italian regulation establishes limit values for the periodic thermal transmittance of walls and roofs through the Decreto Interministeriale 26 giugno 2015 [66].
Also, the similarity relationships found through the cluster analysis between the regions of the countries suggest the possibility of establishing a community framework that regulates both the climate classification between different countries and the requirements for buildings. As a result, a new bioclimatic classification for all South American countries could be developed to establish reference values between different countries and to reduce the inequalities between the energy performance of the buildings built in different regions. In addition, this new regulatory framework should consider the possible limitations presented by each country (e.g., economic limitations) to allow a sustainable development of the building stock.

Conclusions
This study analyzed the regulatory framework of the properties of the building envelope in countries of South America and Europe. Particularly, regulations on energy efficiency of buildings of Argentina, Brazil, Chile, France, Portugal, and Spain were analyzed. Comparisons were conducted with 12 simulated case studies, which were configured with the thermal demands for envelopes established by each country for their climate zones.
Results showed different tendencies between the regulation and the climate zones of the various countries. One of the most important aspects is the high energy demand of buildings built according to the limit values established in the Brazilian regulation. In addition, tendencies of performance clearly different between the South American and the European countries were found, with the latter being those with the lowest energy demands. A detailed analysis conducted by the technical bodies of the South American countries to improve the energy performance of their buildings would reduce these differences. This aspect should be understood as a process of constant evolution similar to what happened in the European countries, which have updated their energy regulations over the years. Nevertheless, there were differences in the energy performance of the buildings located in different climate regions of the European countries, thus leading to the need to review the limit values established by the state regulations of the European countries to guarantee the removal of the existing energy differences between the buildings built in different regions of the same country. In this sense, one of the highlights in the regulations of the various countries is that establishing limitations according to summer climate conditions is not considered. This aspect becomes important in countries such as Spain, where the main energy contribution in some of its climate zones is due to cooling.
The cluster analysis conducted between the different climate zones was also useful to highlight similarity patterns between various regions of the same continent. The subsequent analysis of the distributions of energy demand revealed that buildings located in similar climates but in different countries present energy performances significantly different, thus leading to the same problem reflected between the energy differences in buildings of the same country. As occurs at a country scale, the development of regulations limiting the differences of energy performance between regions should be guaranteed at a continental scale. Climate analysis between countries to establish a valid climate classification for a whole continent, the proposal of new limit values, and even the use of other variables such as periodic thermal transmittance should be aspects to be reviewed by the leaders of countries.
To conclude, the contribution of this research to the energy saving of buildings is that limitations were found in the regulations of their envelopes. The efforts made by the governments of the countries analyzed to establish controls in the thermal parameters of the building envelopes to ensure an acceptable energy performance were highlighted. However, based on the results of this research, differences were found in the energy demand, thereby opening the discussion on the need for new criteria when establishing these policies at a state level. The development of more demanding policies related to the thermal properties of buildings and the analysis at a continental level could reduce the differences between countries and guarantee a more sustainable life for the building stock.

Limitations and Future Work
Further steps of this research will be focused on the energy analysis of actual buildings built in accordance with the regulations of the various countries. One of the limitations of this study is that the energy analysis was carried out with simulations. Although EnergyPlus has a good performance in the results obtained in many studies, the use of actual data would allow the existing discussion between the differences in the regulations of buildings to be deeply analyzed.
Moreover, new possibilities in the thermal properties of different countries and the possibilities of using global criteria of climate classification to establish policies at a continental scale should be analyzed. In this sense, the control of the thermal mass, the periodic thermal properties, the solar factor, etc., could constitute new possibilities of thermal regulation.