Correlations between GIS-Based Urban Building Densification Analysis and Climate Guidelines for Mediterranean Courtyards

sustainability Article Correlations between GIS-Based Urban Building Densification Analysis and Climate Guidelines for Mediterranean Courtyards Juan Rojas-Fernández, Carmen Galán-Marín * ID , Jorge Roa-Fernández ID and Carlos Rivera-Gómez Departamento de Construcciones Arquitectónicas 1, Escuela Técnica Superior de Arquitectura, Universidad de Sevilla, Avda. Reina Mercedes, 2, 41012 Seville, Spain; jmr[email protected] (Ju.R.-F.); [email protected] (Jo.R.-F.); [email protected] (C.R.-G.) *Correspondence: [email protected]; Tel.: +34-954-556591 Received: 1 November 2017; Accepted: 28 November 2017; Published: 6 December 2017 Abstract: This study identifies and proposes A GIS-based exploration of the relationships between aspect ratio of inner courtyards, porosity of the urban fabric and the climatic factors where it is located. To perform that comparison, morphological and measurement methods have been used to delineate spatial boundaries of urban densification. This methodology has been applied to a case study in Spain, where regulation establishes several climatic zones. Examples of cities in these zones have been examined to establish possible correlations. This paper analyses the particularities of these different urban scenarios, considering the effects of climate on the real urban densification. The purpose of this study is to find a relationship between the historical inner courtyards dimensions and the climate of the zone where they are located. In order to frame the real thermal behaviour of the inner courtyard in the context of the vernacular typologies studied, a representative sample of inner courtyards has been selected. The monitoring data presented allow quantifying the courtyard’s ability to temper the maximum temperature values. Keywords: urban densification; GIS; inner courtyards; urban microclimate; courtyard design 1. Introduction Among all the passive-cooling systems, the inner courtyard is one of the most effective and is used, primarily in warm climates. This effect is favourable during both winter and summer [ 1 ], and is more significant in the latter. In fact, there is a relationship between urban geometry, specifically in the layout and proportion of full and empty volumes and the distribution of urban heat islands in cities [2]. The most significant thermal phenomenon of a city in relation to the climate is the so-called urban heat island (UHI). The UHI intensity is the temperature difference between an urban and a rural site under the same climate conditions. Cities and towns are warmer at night than rural areas due to the absorption of solar radiation by the urban pavements and buildings. Urban morphology parameters, such as urban plan area density, geometry of the buildings and topographical features influence airflows in and around buildings and energy consumption on a regional scale [ 2 , 3 ]. In the same line, Jurelionis and Bouris [ 4 ] applied computational fluid dynamics methods in order to calculate surface pressure distributions on building surfaces for three city models and two wind directions. From another perspective, Garcia-Nevado et al. analysed the solar performance at the urban canyon intersections [5]. The UHI effect in our cities will be especially important in the future scenario of climate change. Recent measurements in Manchester show a summer maximum UHI intensity of 8 ◦ C [ 6 ]. In view of Sustainability 2017,9, 2255; doi:10.3390/su9122255 www.mdpi.com/journal/sustainability Sustainability 2017,9, 2255 2 of 26 the negative UHI effects, many researchers have analysed mitigation strategies by simulating single blocks or neighbourhoods [ 7 , 8 ]. Some results have shown the importance of urban design on the microclimate of outdoor spaces [ 9 – 11 ]. Urban density plays an important role in the UHI effect, since a denser urban form results in multiple reflections of solar energy, and influences air convection [ 12 , 13 ]. In this research we focused on “patios”, i.e., open inner courtyards or open-air atriums, which are very common in Spanish or Spanish-American houses among other warm regions. Previous researchers have proven that courtyards show thermal mitigation properties in warm climates such as Mediterranean ones, with a range of temperatures up to 8 ◦ C lower inside the courtyard than the outer space during the warmest hours of the day [ 14 , 15 ]. Al-Hemiddi et al. concluded that the use of courtyards is an applicable strategy during the warmest periods in desert regions [ 16 ]. Cantón et al. found that the performance of inner courtyards at night is useful due to the higher convective and radiative cooling capacity of open spaces [ 17 ]. Kubota et al. identified the thermal functions of internal traditional Chinese courtyards [ 18 ] and Taleghani et al. also considered the most severe climate scenario for the Netherlands for the year 2050. Urban heat mitigation strategies that moderate the microclimate of courtyards were investigated [ 19 ]. In this sense, due to their thermal heat mitigation up to 8 ◦ C, the presence of courtyards in cities, their size and geometric characteristics, would imply a possible way to mitigate the UHI effects. The interactions between urban geometry and surface properties under a specific climate generate microclimates. These interactions were first discussed by Olgyay [ 20 ], Oke [ 21 ] and Givoni [ 22 ]. They analysed the thermal impact of urban typologies in different climates and concluded general design guidelines. They stated that architectural forms, surface materials and urban morphology can affect the microclimate environment. On this topic, courtyard blocks were studied in several climates implying different benefits. A comprehensive study on urban courtyards was done by Yezioro et al. [23] using the SHADING program. Steemers et al. [ 24 ] proposed six archetypical generic urban forms for London. They concluded that large courtyards are environmentally adequate in cold climates, where they can act as sun concentrators and retain their sheltering effect against cold winds under certain geometrical conditions. This is to say, urban geometry shaped by the building typology, has opposite effects for different seasons, satisfying a demand for compactness in summer, to ensure protection from the sunlight, and openness in winter, to provide solar access. At this point it seems to be interesting for the development of these studies to be able to compare different urban fabrics. Considering the amount of data required for the analysis, Geographic Information System (GIS) tools are most adequate to do this. GIS is a system of hardware, software, data, people, organisations and institutional arrangements for the collection, storage, analysis and dissemination of information about areas of the Earth [ 24 , 25 ]. In general, GIS measures aspects of geographic phenomena as processes; they display these measurements, usually in the form of a computer database, so as to emphasise spatial themes, entities and relationships. Assuming the current scenario regarding the risk of climate change, the relationship between urban geometry and microclimate is a relevant topic for both urban planning and urban climatology, as it significantly influences the thermal comfort of individuals and new energy efficiency requirements. This research is supported on the existence of previous empirical results of courtyard microclimates due to its dimensional characteristics [ 14 – 18 ]. The aim of the present paper is to contrast if these courtyard microclimates have a consequence and a correlation with vernacular typologies of courtyards in the different Spanish climatic zones. Previous research [ 26 – 31 ] was usually based on specific case studies but this paper presents several urban scale studies considering the geometry of thousands of courtyards. GIS allows us to identify a statistical relationship between the proportion and geometric characteristics of the courtyards and the climate where they are located. 2. Methodology The tool used was QGIS [ 32 ] release 2.18, the leading Open Source GIS. QGIS supports numerous vector, raster, and database formats and functionalities. Sustainability 2017,9, 2255 3 of 26 In general, there are two basic methods in GIS to do overlay analysis: Entities overlay (in our case field polygons) and overlay on raster data models. The entities overlay was used in this research to identify the polygons that fulfil certain criteria. Data collection was done by means of Shapefile vector files, generated by the Dirección General del Catastro [ 33 ], which belongs to the Spanish Ministry. These files follow the INSPIRE [ 34 ] (Infrastructure for spatial information in Europe European) Directive. The INSPIRE Directive aims to create a European Union spatial data infrastructure for the purposes of EU environmental policies and regulations which may have an impact on the environment. This European Spatial Data Infrastructure enables the sharing of environmental spatial information among public sector organizations, facilitating public access to spatial information across Europe and assisting in policy-making across boundaries. A preliminary GIS analysis led us to focus on the data contained in the constructed space and parcels layers of these files that contain the information about the constructed areas of the city and empty spaces (inner courtyards) including also number and distribution of levels inside every building plot. The area considered corresponds to the historic centre of each city according to local urban regulations. The limits between the streets and the built elements were defined and the heights of the different constructions were related to each of them. Figure 1shows an example (Córdoba) where every building plot that contains an inner courtyard has been marked (different colours are used depending on the courtyard size). Courtyards or inner courtyards are considered, on the condition that they are not in the facades or limited by the streets. Sustainability 2017, 9, 2255 3 of 26 In general, there are two basic methods in GIS to do overlay analysis: Entities overlay (in our case field polygons) and overlay on raster data models. The entities overlay was used in this research to identify the polygons that fulfil certain criteria. Data collection was done by means of Shapefile vector files, generated by the Dirección General del Catastro [33], which belongs to the Spanish Ministry. These files follow the INSPIRE [34] (Infrastructure for spatial information in Europe European) Directive. The INSPIRE Directive aims to create a European Union spatial data infrastructure for the purposes of EU environmental policies and regulations which may have an impact on the environment. This European Spatial Data Infrastructure enables the sharing of environmental spatial information among public sector organizations, facilitating public access to spatial information across Europe and assisting in policy-making across boundaries. A preliminary GIS analysis led us to focus on the data contained in the constructed space and parcels layers of these files that contain the information about the constructed areas of the city and empty spaces (inner courtyards) including also number and distribution of levels inside every building plot. The area considered corresponds to the historic centre of each city according to local urban regulations. The limits between the streets and the built elements were defined and the heights of the different constructions were related to each of them. Figure 1 shows an example (Córdoba) where every building plot that contains an inner courtyard has been marked (different colours are used depending on the courtyard size). Courtyards or inner courtyards are considered, on the condition that they are not in the facades or limited by the streets. Figure 1. Córdoba city centre, every construction that contains an inner courtyard was marked. Data processing allowed us to calculate the Porosity Index (PI) of every block and the percentage of plots with inner courtyards. PI is a parameter that provides an overview of the historical centre, how perforated it is, as a general ratio between solid and void in the studied area. A higher PI means more voids. This is to say, an empty plot has a porosity value of 100, while a 0 value means a fully dense plot without courtyards. Neat Porosity Index (NPI) was calculated considering only the urban plots that contain a courtyard. All public spaces such as street areas, squares, etc. have not been considered in the calculations affecting only the insight of the built plot both for PI and NPI. In the final Appendix A detail, data and plans that reflect the specific situation of each of the cities analysed are showed. Figures A1–A6 in the Appendix A represent in a bar chart, the most typical inner courtyards area for every city, and so the most representative inner courtyards were chosen (those whose area is between 5–15 m2 and 15–30 m2). Also, the average height of the construction around the courtyard was determined. The tendency of historical courtyards to possess square dimensions allows us to easily determine the width. This simplification is used to calculate Figure 1. Córdoba city centre, every construction that contains an inner courtyard was marked. Data processing allowed us to calculate the Porosity Index (PI) of every block and the percentage of plots with inner courtyards. PI is a parameter that provides an overview of the historical centre, how perforated it is, as a general ratio between solid and void in the studied area. A higher PI means more voids. This is to say, an empty plot has a porosity value of 100, while a 0 value means a fully dense plot without courtyards. Neat Porosity Index (NPI) was calculated considering only the urban plots that contain a courtyard. All public spaces such as street areas, squares, etc. have not been considered in the calculations affecting only the insight of the built plot both for PI and NPI. In the final Appendix Adetail, data and plans that reflect the specific situation of each of the cities analysed are showed. Figures A1–A6 in the Appendix Arepresent in a bar chart, the most typical inner courtyards area for every city, and so the most representative inner courtyards were chosen (those whose area is between 5–15 m 2 and 15–30 m 2 ). Also, the average height of the construction around the Sustainability 2017,9, 2255 4 of 26 courtyard was determined. The tendency of historical courtyards to possess square dimensions allows us to easily determine the width. This simplification is used to calculate the Aspect Ratio (AR) of the courtyard (Figure 2). AR, is the correlation between the height and width of the inner courtyards as described by Hall [35]: AR = hmax/W. where hmax = maximum height of inner courtyards and W = width of inner courtyard (inner courtyards were considered square in the present study). Sustainability 2017, 9, 2255 4 of 26 the Aspect Ratio (AR) of the courtyard (Figure 2). AR, is the correlation between the height and width of the inner courtyards as described by Hall [35]: AR = hmax/W. where hmax = maximum height of inner courtyards and W = width of inner courtyard (inner courtyards were considered square in the present study). In the specific literature, there are several studies that relate AR to heat flows in urban settings [36] and with the albedo heterogeneity in cities [37]. Figure 2. Aspect Ratio (AR = h/W) of an inner courtyards. 3. Case Study Meteorological and climatic conditions of cities constitute a relevant issue for urban design and urban studies, as they affect human thermal comfort both outdoors and indoors, influencing the appreciation and use of open spaces and, indirectly, the energy consumption of buildings for heating, cooling and ventilation. These issues have been reflected in the urban and constructive regulations of the different countries. 3.1. Spanish Regulations In the present study, the distribution and size of the courtyards in different cities of the Spanish geography are analysed. The research tries to establish a relation between the geometric characteristics of the courtyards and the different climatic zones. In order to calculate the different climatic zones, it is necessary to obtain the parameters of Winter Severity Index (WSI) and Summer Severity Index (SSI). These values, for each location, are calculated with the statistical average temperature during the months of winter and summer respectively. If it is considered an excessively low or excessively high temperature, energy demands for heating or cooling are involved. The WSI is given in the Spanish regulations [38], from lowest to highest, by the letters A–E (Figure 3a). In addition, the SSI, by numbers 1–4, where 1 refers to the smallest and 4 the highest. There is no specific map published in [38] for SSI index. According to these standards, Table 1 displays columns corresponding to all winter classifications, being different summer severity ranks grouped in several cases. Figure 2. Aspect Ratio (AR = h/W) of an inner courtyards. In the specific literature, there are several studies that relate AR to heat flows in urban settings [ 36 ] and with the albedo heterogeneity in cities [37]. 3. Case Study Meteorological and climatic conditions of cities constitute a relevant issue for urban design and urban studies, as they affect human thermal comfort both outdoors and indoors, influencing the appreciation and use of open spaces and, indirectly, the energy consumption of buildings for heating, cooling and ventilation. These issues have been reflected in the urban and constructive regulations of the different countries. 3.1. Spanish Regulations In the present study, the distribution and size of the courtyards in different cities of the Spanish geography are analysed. The research tries to establish a relation between the geometric characteristics of the courtyards and the different climatic zones. In order to calculate the different climatic zones, it is necessary to obtain the parameters of Winter Severity Index (WSI) and Summer Severity Index (SSI). These values, for each location, are calculated with the statistical average temperature during the months of winter and summer respectively. If it is considered an excessively low or excessively high temperature, energy demands for heating or cooling are involved. The WSI is given in the Spanish regulations [ 38 ], from lowest to highest, by the letters A–E (Figure 3a). In addition, the SSI, by numbers 1–4, where 1 refers to the smallest and 4 the highest. There is no specific map published Sustainability 2017,9, 2255 5 of 26 in [ 38 ] for SSI index. According to these standards, Table 1displays columns corresponding to all winter classifications, being different summer severity ranks grouped in several cases. Sustainability 2017, 9, 2255 5 of 26 For the limitation of energy demand, the Spanish regulations [38], establish different climatic zones, identified by a letter, corresponding to the winter division, and a number, corresponding to the summer division. In this way, twelve structured climatic zones are established according to the following table and map. Table 1. Classification of Spanish climatic zones as per national regulations [38]. SSI (Summer) A4 B4 C4 E1 A3 B3 C3 D3 C2 D2 C1 D1 WSI (Winter) (a) (b) Figure 3. (a) Geographic distribution of Spanish climatic zones per CTE [38]; (b) Location of the different cities considered in the study. 3.2. Cities Studied To perform a study sufficiently representative of the typological variety of urban structures, seven cities were selected from the twelve above-mentioned climatic zones. The study focuses on the relation between urban courtyard typology and climate zones, starting from the hypothesis that there is an adaptation of the constructive solutions to the microclimatic possibilities of the courtyards in different locations. The selected cities (Figure 3b) were: Malaga (A3), Seville (B4), Cordoba (B4), Toledo (C4), Santiago (C1), Zaragoza (D3) and Burgos (E1). These cities are listed by their WSI, being Malaga the one with the warmest temperatures and Burgos the lowest. However, looking at the SSI, we can notice that Seville, Cordoba and Toledo all have higher climatic severities in summer compared to Malaga and Zaragoza, while Santiago and Burgos are the coolest. The selection included cities in the most extreme climatic zones (A3–E1) and the analysis was repeated in cities with different urban configurations but a similar climatic zone in order to corroborate the direct relationship between the geometry of the inner courtyards and the climate of the city, as in the case of Seville and Cordoba, both B4. From the cities selected, samples of the urban layout corresponding to the oldest part of the city or historic centre were taken. This was done to avoid the most recent areas where current urban regulations have determined standardised courtyard geometry. 3.3. Results All the seven Spanish cities mentioned have been analysed. City centres were delimited as representatives of the vernacular architecture. Table 2 shows the results of courtyard percentages in the seven different climatic zones analysed and the total number of courtyards for each of the cities Figure 3. ( a ) Geographic distribution of Spanish climatic zones per CTE [ 38 ]; ( b ) Location of the different cities considered in the study. Table 1. Classification of Spanish climatic zones as per national regulations [38]. SSI (Summer) A4 B4 C4 E1 A3 B3 C3 D3 C2 D2 C1 D1 WSI (Winter) For the limitation of energy demand, the Spanish regulations [ 38 ], establish different climatic zones, identified by a letter, corresponding to the winter division, and a number, corresponding to the summer division. In this way, twelve structured climatic zones are established according to the following table and map. 3.2. Cities Studied To perform a study sufficiently representative of the typological variety of urban structures, seven cities were selected from the twelve above-mentioned climatic zones. The study focuses on the relation between urban courtyard typology and climate zones, starting from the hypothesis that there is an adaptation of the constructive solutions to the microclimatic possibilities of the courtyards in different locations. The selected cities (Figure 3b) were: Malaga (A3), Seville (B4), Cordoba (B4), Toledo (C4), Santiago (C1), Zaragoza (D3) and Burgos (E1). These cities are listed by their WSI, being Malaga the one with the warmest temperatures and Burgos the lowest. However, looking at the SSI, we can notice that Seville, Cordoba and Toledo all have higher climatic severities in summer compared to Malaga and Zaragoza, while Santiago and Burgos are the coolest. The selection included cities in the most extreme climatic zones (A3–E1) and the analysis was repeated in cities with different urban configurations but a similar climatic zone in order to corroborate the direct relationship between the geometry of the inner courtyards and the climate of the city, as in the case of Seville and Cordoba, both B4. From the cities selected, samples of the urban layout corresponding to the oldest part of the city or historic centre were taken. This was done to avoid the most recent areas where current urban regulations have determined standardised courtyard geometry. Sustainability 2017,9, 2255 6 of 26 3.3. Results All the seven Spanish cities mentioned have been analysed. City centres were delimited as representatives of the vernacular architecture. Table 2shows the results of courtyard percentages in the seven different climatic zones analysed and the total number of courtyards for each of the cities in the city centre area. Note that the city maps are not represented on the same scale, but depending on the total size of the city. These maps allow us to calculate the porosity index of every city and the percentage of plots with courtyards, as already summarized in Table 2. In spite of the fact that due to its size the cities differ from 919 urban plots in Burgos to 8139 urban plots in the case of Seville, these different sizes allow a more objective calculation of the neat porosity of the city. Table 2. Porosity index and percentage of plots with courtyard of every city analysed. BU CO MA SE SA TO ZA Units Urban plots 919 4625 2900 8139 1397 2542 2849 Units Plots with courtyard 560 3790 1470 6263 575 1649 2164 % Percentage 61 82 51 77 41 65 76 m2Total Courtyard Surface 43,028 267,956 893,08 384,504 56,077 87,632 200,522 % PI 10 15 5 12 11 10 14 % NPI 17 19 11 16 28 15 18 BU = Burgos, CO = Cordoba, MA = Malaga, SE = Seville, SA = Santiago, TO = Toledo, ZA = Zaragoza. NPI provides an orientation of the relation of the plots with courtyards. Santiago for example, has very few inner courtyards (only 41% of the plots). Nevertheless, their size is bigger (NPI = 28). Besides, 82% of the plots in Cordoba include courtyards (the largest proportion), displaying however a porosity like Zaragoza’s, i.e., in spite of the higher number of courtyards per plot, they present a smaller surface. According to Table 2, the total number of plots with courtyards and the total percentage of them show how rooted the courtyard culture is in some cities, basically due to their Mediterranean tradition. Seville and Cordoba exceed 6000 and 3700 plots with courtyards, respectively. Table 3. Number of inner courtyards between 5 and 15 m2for every city the analysed. Height of the Building (No. of Levels) I II III IV V VI VII VIII IX X XI XII Malaga Total no. of courtyards 8 97 199 270 174 97 40 28 16 11 1 1 MA-A3 Total (%) 1 10 21 29 18 10 4 3 2 1 0 0 Seville Total no. of courtyards 59 532 2015 2278 971 186 32 20 13 20 0 SE-B4 Total (%) 1 9 33 37 16 3 1 0 0 0 0 0 Cordoba Total no. of courtyards 115 1248 1124 609 353 114 43 6 6 3 0 0 CO-B4 Total (%) 3 34 31 17 10 3 1 0 0 0 0 0 Toledo Total no. of courtyards 0 357 583 270 56 5 0 0 0 0 0 0 TO-C4 Total (%) 0 28 46 21 4 0 0 0 0 0 0 0 Santiago Total no. of courtyards 20 42 111 88 25 9 78 0 20 0 SA-C1 Total (%) 6 13 36 28 8 3 2 3 0 1 0 0 Zaragoza Total no. of courtyards 30 24 109 332 509 337 164 58 30 17 81 ZA-D3 Total (%) 2 1 7 20 31 21 10 4 2 1 0 0 Burgos Total no. of courtyards 12 14 10 45 117 87 28 20 2010 BU-E1 Total (%) 4 4 3 13 35 26 8 6 1 0 0 0 Sustainability 2017,9, 2255 7 of 26 Conversely, the number of courtyards in Toledo, Zaragoza and Malaga is less between 1470 and 2164 and, lastly, about 500 in Burgos and Santiago. On the other hand, the porosity index remains between 10% and 15% for all cities except Malaga, indicating that despite having fewer plots with courtyards, the ratio between built and unbuilt spaces remains constant. Comparing the results, the most typical sizes of courtyards at this domestic scale were 5–15 m 2 and 15–30 m 2 . These two sizes have been studied in depth and results are shown in Table 3. Herein, the height of the building (in number of levels/floors) detected for these inner courtyards is presented. In order to establish how, certain geometric characteristics of the inner courtyards in traditional buildings are related to the climate in which they are constructed, the influence of the AR is studied. In Tables 3and 4the first row refers to the height of the building (number of levels, in Roman numbers) while in Tables 5and 6the first row shows AR (Aspect Ratio, in Arabic numbers). Table 4. Number of inner courtyards between 15 and 30 m2for every city the analysed. Height of the Building (No. of Levels) I II III IV V VI VII VIII IX X XI XII Malaga Total no. of courtyards 5 64 118 168 143 46 38 29 25 10 15 MA-A3 Total (%) 1 10 18 26 22 7 6 4 4 2 0 1 Seville Total no. of courtyards 53 353 913 625 199 32 24 31 5 0 0 0 SE-B4 Total (%) 2 16 41 28 9 1 1 1 0 0 0 0 Cordoba Total no. of courtyards 96 882 476 146 97 35 45 15 19 6 0 0 CO-B4 Total (%) 5 49 26 8 5 2 2 1 1 0 0 0 Toledo Total no. of courtyards 0 180 252 84 31 6 0 0 0 0 0 0 TO-C4 Total (%) 0 33 46 15 6 1 0 0 0 0 0 0 Santiago Total no. of courtyards 10 51 75 41 10 4020 0 0 0 SA-C1 Total (%) 5 26 39 21 5 2 0 1 0 0 0 0 Zaragoza Total no. of courtyards 27 108 280 259 201 98 25 11 0 0 0 0 ZA-D3 Total (%) 3 11 28 26 20 10 2 1 0 0 0 0 Burgos Total no. of courtyards 723 12 25 41 41 34 27 1 1 0 0 BU-E1 Total (%) 3 11 6 12 19 19 16 13 0 0 0 0 Tables 5and 6allow to classify the cities in two different groups: those cities with low heights and low AR, and those with high heights and high AR. Different heights obey to different urban conceptions: those cities with more Muslim-court culture, have maintained lower building heights balancing the small surface of the courtyards (more numerous and spread) in the search for an efficient Aspect Ratio (AR: 2.00–2.80–2.60). These are Seville, Toledo and Córdoba, with heights around 3 levels. Figures 4and 5allow to compare the results obtained. Table 5. Numerical values for AR calculated for inner courtyards between 5 and 15 m2. AR 1 2 3 4 5 6 7 8 9 10 11 12 Malaga Total no. of courtyards 489 213 299 169 77 47 25 15 40 0 MA-A3 Total (%) 0 9 23 32 18 8 5 3 2 0 0 0 Seville Total no. of courtyards 52 557 2178 2167 883 188 58 16 2 7 0 0 SE-B4 Total (%) 1 9 36 35 14 3 1 0 0 0 0 0 Sustainability 2017,9, 2255 8 of 26 Table 5. Cont. AR 1 2 3 4 5 6 7 8 9 10 11 12 Cordoba Total no. of courtyards 94 1271 1227 594 275 104 40 10 6 0 0 0 CO-B4 Total (%) 3 35 34 16 8 3 1 0 0 0 0 0 Toledo Total no. of courtyards 0 253 542 343 104 24 4 1 0 0 0 0 TO-C4 Total (%) 0 20 43 27 8 2 0 0 0 0 0 0 Santiago Total no. of courtyards 10 35 89 96 42 19 12 513 0 0 SA-C1 Total (%) 3 11 29 31 13 6 4 2 0 1 0 0 Zaragoza Total no. of courtyards 19 38 120 298 430 343 189 106 34 20 14 7 ZA-D3 Total (%) 1 2 7 18 27 21 12 7 2 1 1 0 Burgos Total no. of courtyards 614 14 45 85 78 58 27 7 1 01 BU-E1 Total (%) 2 4 4 13 25 23 17 8 2 0 0 0 Sustainability 2017, 9, 2255 8 of 26 SA-C1 Total no. of courtyards Total (%) 3 11 29 31 13 6 4 2 0 1 0 0 Zaragoza Total no. of courtyards 19 38 120 298 430 343 189 106 34 20 14 7 ZA-D3 Total (%) 1 2 7 18 27 21 12 7 2 1 1 0 Burgos Total no. of courtyards 6 14 14 45 85 78 58 27 7 1 0 1 BU-E1 Total (%) 2 4 4 13 25 23 17 8 2 0 0 0 Figure 4. AR calculated for inner courtyards between 5 and 15 m 2 for every city the analysed. Table 6. Numerical values for AR calculated for inner courtyards between 15 and 30 m 2 . AR 1 2 3456789 10 11 12 Malaga Total no. of courtyards 9 140 248 145 46 39 22 2 1 1 1 0 MA-A3 Total (%) 1 21 38 22 7 6 3 0 0 0 0 0 Seville Total no. of courtyards 124 1062 862 131 36 18 2 0 0 0 0 0 SE-B4 Total (%) 6 48 39 6 2 1 0 0 0 0 0 0 Cordoba Total no. of courtyards 294 1104 247 86 51 31 3 1 0 0 0 0 CO-B4 Total (%) 16 61 14 5 3 2 0 0 0 0 0 0 Toledo Total no. of courtyards 0 390 146 17 0 0 0 0 0 0 0 0 TO-C4 Total (%) 0 71 26 3 0 0 0 0 0 0 0 0 Santiago Total no. of courtyards 19 97 61 13 2 1 0 0 0 0 0 0 SA-C1 Total (%) 10 50 32 7 1 1 0 0 0 0 0 0 Zaragoza Total no. of courtyards 27 108 280 259 201 98 25 11 0 0 0 0 ZA-D3 Total (%) 3 11 28 26 20 10 2 1 0 0 0 0 Burgos Total no. of courtyards 15 26 35 62 54 17 3 0 0 1 0 0 BU-E1 Total (%) 7 12 16 29 25 8 1 0 0 0 0 0 Figure 4. AR calculated for inner courtyards between 5 and 15 m2for every city the analysed. Table 6. Numerical values for AR calculated for inner courtyards between 15 and 30 m2. AR 1 2 3 4 5 6 7 8 9 10 11 12 Malaga Total no. of courtyards 9 140 248 145 46 39 22 2 1 1 1 0 MA-A3 Total (%) 1 21 38 22 7 6 3 0 0 0 0 0 Seville Total no. of courtyards 124 1062 862 131 36 18 200000 SE-B4 Total (%) 6 48 39 6 2 1 0 0 0 0 0 0 Cordoba Total no. of courtyards 294 1104 247 86 51 31 3 10 0 0 0 CO-B4 Total (%) 16 61 14 5 3 2 0 0 0 0 0 0 Sustainability 2017,9, 2255 9 of 26 Table 6. Cont. AR 1 2 3 4 5 6 7 8 9 10 11 12 Toledo Total no. of courtyards 0 390 146 17 00000000 TO-C4 Total (%) 0 71 26 3 0 0 0 0 0 0 0 0 Santiago Total no. of courtyards 19 97 61 13 2 1 0 0 0 0 0 0 SA-C1 Total (%) 10 50 32 7 1 1 0 0 0 0 0 0 Zaragoza Total no. of courtyards 27 108 280 259 201 98 25 11 0 0 0 0 ZA-D3 Total (%) 3 11 28 26 20 10 2 1 0 0 0 0 Burgos Total no. of courtyards 15 26 35 62 54 17 3 0 0 10 0 BU-E1 Total (%) 7 12 16 29 25 8 1 0 0 0 0 0 Sustainability 2017, 9, 2255 9 of 26 Figure 5. AR calculated for inner courtyards between 15 and 30 m 2 for every city the analysed. On the contrary, Burgos and Zaragoza have an average height above 5 levels, yet due to different reasons. Zaragoza belongs to a modern urbanism reflected in two very well defined types of courtyard: the small ventilation courtyard surrounded by high heights (AR: 5.30), and larger courtyards (15–30 m 2 ) with consistently high heights (AR: 2.3 balanced for large inner courtyards). In the case of Burgos (medieval centre), both types of courtyard maintain high heights with small surfaces (AR: higher than 4.50 both cases). 3.4. Analysis Table 7 shows a summary of the different data obtained for each city as shown in Figures A1– A7 (Appendix A). In relation to the total number of inner courtyards in the historic centre of each city, data confirms that those cities with highest SSI (Córdoba, Seville and Toledo) are those presenting a bigger number of courtyards (between 2805 and 13,539 units). An exceptional case is Zaragoza, due to modern urban reconfiguration of its historic centre. With a historic centre composed largely of buildings with small services inner courtyards in multi-family dwellings of 4–5 storeys high. At the opposite end, Burgos and Santiago, with minimum SSI and a much lower number of courtyards (897–929 units). Malaga, with an intermediate SSI, has also an intermediates numbers of courtyards (2998 units). Table 7. Summary of the main data obtained from the analysis of the different cities. BU CO MA SE SA TO ZA 1 UNITS No. of COURTYARDS 897 8114 2998 13,539 929 2805 4235 m 2 Standard area 8 9 9 9.5 9 7 11.25 Size 5 – 15 m 2 No. of COURTYARDS 338 3621 942 6108 312 1271 1620 No. of levels 5.24 3.12 4.37 3.25 4.00 3.03 5.22 h/w AR 4.7 2.0 3.8 2.8 3.0 2.6 5.1 Size 15 – 30 m 2 No. of COURTYARDS 213 1817 654 2235 193 553 1009 No. of levels 5.30 2.88 4.68 2.99 3.06 2.97 3.94 h/w AR 4.6 1.2 2.9 2.3 1.9 1.2 2.3 1 BU = Burgos, CO = Cordoba, MA = Malaga, SE = Seville, SA = Santiago, TO = Toledo, ZA = Zaragoza. Figure 5. AR calculated for inner courtyards between 15 and 30 m2for every city the analysed. On the contrary, Burgos and Zaragoza have an average height above 5 levels, yet due to different reasons. Zaragoza belongs to a modern urbanism reflected in two very well defined types of courtyard: the small ventilation courtyard surrounded by high heights (AR: 5.30), and larger courtyards (15–30 m 2 ) with consistently high heights (AR: 2.3 balanced for large inner courtyards). In the case of Burgos (medieval centre), both types of courtyard maintain high heights with small surfaces (AR: higher than 4.50 both cases). 3.4. Analysis Table 7shows a summary of the different data obtained for each city as shown in Figures A1–A7 (Appendix A). In relation to the total number of inner courtyards in the historic centre of each city, data confirms that those cities with highest SSI (Córdoba, Seville and Toledo) are those presenting a bigger number of courtyards (between 2805 and 13,539 units). An exceptional case is Zaragoza, due to modern urban reconfiguration of its historic centre. With a historic centre composed largely of buildings with small services inner courtyards in multi-family dwellings of 4–5 storeys high. At the opposite end, Burgos and Santiago, with minimum SSI and a much lower number of courtyards (897–929 units). Malaga, with an intermediate SSI, has also an intermediates numbers of courtyards (2998 units). Sustainability 2017,9, 2255 16 of 26 Sustainability 2017, 9, 2255 16 of 26 Figure 11. Registered air temperature drop inside the monitored courtyard in Malaga (September). AR = 3.66. Figure 11. Registered air temperature drop inside the monitored courtyard in Malaga (September). AR = 3.66. Sustainability 2017,9, 2255 17 of 26 5. Conclusions A clear relationship between the geometrical characteristics of the courtyards and the climate zones where they are located can be established for the analysed cities. This study shows the relation between traditional architecture and the local environment. It therefore seeks the evidence that the architecture and geometry of the courtyards must modulate some characteristics of the internal microclimate, as certain shapes entail different energy consequences for the building according to the climate context. However, new regulations in Spain have standardized inner courtyards size without taking into account the adaptation of the building to the climate conditions; being this a general trend is the current architecture in Mediterranean cities. The results of this research clearly show the greater prevalence of courtyards in cities with warmer climates. Thus, in cities with climatic zone B4, such as Cordoba, both the PI (15%) and the percentage of plots with courtyards (82%) are the highest. However, NPI indicates that in the studied cities with colder climates, such as Santiago (28%), the courtyards, when existing, are much larger than in warmer climates, where they occupy a greater proportion of the plots where they are located. As it can be seen in Figure A5, these are usually backyards and not inner courtyards as the proposed ones. This city also displays the lowest percentage of plots with an inner courtyard (41%). Inner courtyards tempering properties have already been demonstrated by different authors in these dominant summer climates [ 14 – 19 , 40 ] and checked in the monitored courtyards at a single building scale. The maximum air temperature drop in the period recorded, was 6.7 ◦ C. Therefore, at an urban scale, the city structure that implies a variable presence, AR and sizes of courtyards in these warm-climate cities depending on the specific climate has been also showed in this paper. Despite the fact that night-time temperatures of the roof differ around ± 1 ◦ C with regard to the ones inside the courtyard in the monitored cases, the thermal variation during the day is much higher and has a tempering effect that contributes globally to diminish the UHI effect. To conclude, the link between the vernacular urban structure of the courtyards and the different climate conditions in the studied cities, remarks the importance of taking into consideration design strategies, such as building shape, in order to balance the summer severity effect in Mediterranean climates. Acknowledgments: The authors wish to acknowledge the IUACC “Instituto Universitario de Arquitectura y Ciencias de la Construcción” for the necessary support to develop this research. This work and the costs to publish in open access have been partially funded by has been supported by the Andalusian Government Research project TEP-7985 and the National Government of Spain Research Project MTM2015-64577-C2-2-R. Author Contributions: Galán-Marín, Rivera-Gómez and Rojas-Fernández conceived and designed the experiments; Roa-Fernández performed the experiments; Galán-Marín and Rivera-Gómez analyzed the data and wrote the paper. Conflicts of Interest: The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results. Sustainability 2017,9, 2255 18 of 26 Appendix A Sustainability 2017, 9, 2255 18 of 26 Appendix A Figure A1. Plan (left) with distribution of courtyards in Malaga city centre; Courtyard sizes (right). Figure A1. Plan (left) with distribution of courtyards in Malaga city centre; Courtyard sizes (right). Sustainability 2017,9, 2255 19 of 26 Sustainability 2017, 9, 2255 19 of 26 Figure A2. Plan (left) with distribution of courtyards in Seville city centre; Courtyard sizes (right). PATIOS SEVILLA SURFACE (m2)RESULTS 0,0 0 0-1 0 1 - 5 1242 5 - 10 4642 10 - 15 2676 15 - 20 1096 20 -25 674 25 -30 468 30 -35 401 35 -40 277 40 -45 255 45 - 50 204 50 - 55 158 55 - 60 142 60 - 70 208 70 - 80 172 80 - 90 127 90 - 100 99 100 - 110 91 110 - 120 60 120 - 140 102 140 - 160 77 160 -200 103 200 -300 145 300 -500 78 500-1000 32 1000 - 3000 10 >3000 0 13539 Figure A2. Plan (left) with distribution of courtyards in Seville city centre; Courtyard sizes (right). Sustainability 2017,9, 2255 20 of 26 Sustainability 2017, 9, 2255 20 of 26 Figure A3. Plan (left) with distribution of courtyards in Córdoba city centre; Courtyard sizes (right). PATIOS CORDOBA SURFACE (m 2 )RESULTS 0,0 0 0-1 0 1 - 5 250 5 - 10 2134 10 - 15 1794 15 - 20 872 20 -25 558 25 -30 410 30 -35 288 35 -40 226 40 -45 209 45 - 50 167 50 - 55 132 55 - 60 118 60 - 70 178 70 - 80 144 80 - 90 100 90 - 100 75 100 - 110 72 110 - 120 55 120 - 140 76 140 - 160 44 160 -200 64 200 -300 71 300 -500 42 500-1000 26 1000 - 3000 9 >3000 0 8114 Figure A3. Plan (left) with distribution of courtyards in Córdoba city centre; Courtyard sizes (right). Sustainability 2017,9, 2255 21 of 26 Sustainability 2017, 9, 2255 21 of 26 Figure A4. Plan (left) with distribution of courtyards in Toledo city centre; Courtyard sizes (right). PATIOS TOLEDO SURFACE (m2)RESULTS 0,0 0 0-1 0 1 - 5 135 5 - 10 820 10 - 15 569 15 - 20 281 20 -25 193 25 -30 149 30 -35 114 35 -40 87 40 -45 51 45 - 50 43 50 - 55 34 55 - 60 34 60 - 70 60 70 - 80 25 80 - 90 19 90 - 100 20 100 - 110 22 110 - 120 14 120 - 140 28 140 - 160 23 160 -200 24 200 -300 34 300 -500 21 500-1000 3 1000 - 3000 2 >3000 0 2805 Figure A4. Plan (left) with distribution of courtyards in Toledo city centre; Courtyard sizes (right). Sustainability 2017,9, 2255 22 of 26 Sustainability 2017, 9, 2255 22 of 26 Figure A5. Plan (left) with distribution of courtyards in Santiago city centre; Courtyard sizes (right). PATIOS SANTIAGO DE C. SURFACE (m 2 )RESULTS 0,0 0 0-1 0 1 - 5 0 5 - 10 215 10 - 15 134 15 - 20 87 20 -25 79 25 -30 48 30 -35 44 35 -40 25 40 -45 26 45 - 50 17 50 - 55 14 55 - 60 14 60 - 70 21 70 - 80 24 80 - 90 18 90 - 100 9 100 - 110 16 110 - 120 19 120 - 140 24 140 - 160 14 160 -200 19 200 -300 30 300 -500 19 500-1000 12 1000 - 3000 1 >3000 0 929 Figure A5. Plan (left) with distribution of courtyards in Santiago city centre; Courtyard sizes (right). Sustainability 2017,9, 2255 23 of 26 Sustainability 2017, 9, 2255 23 of 26 Figure A6. Plan (left) with distribution of courtyards in Zaragoza city centre; Courtyard sizes (right). PATIOS ZARAGOZA SURFACE (m 2 )RESULTS 0,0 0 0-1 0 1 - 5 145 5 - 10 936 10 - 15 749 15 - 20 473 20 -25 308 25 -30 233 30 -35 170 35 -40 130 40 -45 121 45 - 50 116 50 - 55 85 55 - 60 63 60 - 70 91 70 - 80 82 80 - 90 74 90 - 100 49 100 - 110 38 110 - 120 42 120 - 140 68 140 - 160 42 160 -200 61 200 -300 70 300 -500 40 500-1000 36 1000 - 3000 13 >3000 0 4235 Figure A6. Plan (left) with distribution of courtyards in Zaragoza city centre; Courtyard sizes (right). Sustainability 2017,9, 2255 24 of 26 Sustainability 2017, 9, 2255 24 of 26 Figure A7. Plan (left) with distribution of courtyards in Burgos city centre; Courtyard sizes (right). PATIOS BURGOS SURFACE (m 2 )RESULTS 0,0 0 0-1 0 1 - 5 0 5 - 10 221 10 - 15 151 15 - 20 111 20 -25 78 25 -30 47 30 -35 36 35 -40 32 40 -45 17 45 - 50 24 50 - 55 16 55 - 60 19 60 - 70 24 70 - 80 15 80 - 90 14 90 - 100 9 100 - 110 7 110 - 120 4 120 - 140 11 140 - 160 6 160 -200 14 200 -300 16 300 -500 17 500-1000 7 1000 - 3000 1 >3000 0 TOTAL 897 Figure A7. Plan (left) with distribution of courtyards in Burgos city centre; Courtyard sizes (right). Sustainability 2017,9, 2255 25 of 26 References 1. Martinelli, L.; Matzarakis, A. Influence of height/width proportions on the thermal comfort of courtyard typology for Italian climate zones. Sustain. Cities Soc. 2017,29, 97–106. [CrossRef] 2. Srebric, J.; Heidarinejad, M.; Liu, J. Building neighborhood emerging properties and their impacts on multi-scale modeling of building energy and airflows. Build. Environ. 2015,91, 246–262. [CrossRef] 3. Jurelionis, A.; Bouris, D.G. 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