Ambiance through Spatial Organization in Vernacular architecture of hot and dry regions of India – The case of Ahmedabad and Jodhpur

: Most notable vernacular settlements of the past had a potential of generating stimulating ambiance because of their “organicness”. The understanding of the “Nature of order” in this informality can identify the factors or parameters generating the definite spatial character appropriate for the time and place. The spatial character generates the spirit of the place, what we call the genius loci. This paper analyses the relationship of spatial organization and ambiance of the old city settlements in hot and dry climatic regions of two selected cities of India – Ahmedabad and Jodhpur at various levels. Both the selected cities are informal in nature and rich with its ambiance. Space syntax and digital simulations are used to decode the parameters of the spatial organization. The spatial morphology is analysed using tools such as justified graph analysis, visibility graph analysis, isovists analysis, agent movement analysis and sunlight study. The result of the study is summarised in tabular format and presented in a graphical manner for better understanding. This analysis is valuable in the derivation of the constants and variables to define the learning from the vernacular spatial organization.


Overview of Vernacular architecture
The sensibility and logic of vernacular architecture generate quintessential liveable built forms and ambiance of respective settlements. The vernacular has been widely understood as "the architectural language of the people" with its ethnic, regional and local dialects: the product of "non-experts" (Oliver, 2006).
The solutions inherited by vernacular architecture are largely based on necessity, efficiency and prevalent aesthetic sensibilities. The vernacular architecture of any place is based on natural and physical built environment enriched by the cultural heritage of a place and is developed over a long period of time. In the process of growth and evolution, it achieves "wholeness" not only in its totality but also in each fragment. Various building forms are generated in the process of learning from the existing natural environment and building suitably with climatic and social considerations. As a result, the settlements are synergetic with the social, cultural and climatic needs of the region.

Vernacular architecture of hot and dry regions of India
The Indian subcontinent's diverse range of landform and climatic conditions, such as gigantic Himalayan mountains in the north, Indian ocean in the south, hot sandy desert in the west and wetlands of Bengal in the east have generated varieties of built forms across the country. The natural landscape of the site and response to metaphysical concerns, climate, local proficiencies and construction techniques are the personification of the rich vernacular tradition of built form in India. In each location, the vernacular architecture has evolved in a unique way of response to the context. Hot and dry climatic zones are experienced in areas far from sea coasts and usually have a low precipitation rate. The most important aspect to be addressed is protection from harsh sunlight and the usual answer is to develop a built form capable of reducing the radiation.
The most preferred solutions in a hot and dry climate are dense clustering of buildings, which allow for the minimum heat gain in buildings. The streets remain shaded in summer providing comfortable temperature throughout the day for outside activities. Hence even in harsh summers, the streets are walkable during the afternoon. The houses are constructed with thick insulation walls, tiny scale openings to keep the hot air outside, and compact clustering of built forms with mutual shading device and provision of the courtyard as a thermal regulator. The harmonious relationship between the thick walls, jalis (perforated openings), courtyards and transitional spaces of semi-private nature is an intelligent approach to deal with the climate.
The spatial character is at the heart of understanding the physical ambiance of any place. The initial step for understanding the spatial character is to understand the spatial organization and the experience attached with it. The interaction of this dense spatial organization with its culture generates the cohesive ambiance within the settlement. Amos Rapoport emphasized that climate, ecology, material, technology, and local economy act as controls rather than factors which affect the spatial ambiance which is articulated as "The built environment creates a specific microclimate for each site as an outcome of building configuration, its orientation, and arrangement in space. Further, the building element interacts with natural macroclimate to determine the factors affecting comfort: light, heat, wind, and humidity.

Introduction to Case study
Two cities in different geographical locations and cultural contexts in hot and dry climatic regions of India are selected to study the relationship of spatial organization with ambiance. The city of Ahmedabad located in the state of Gujarat and Jodhpur in the state of Rajasthan are selected for the study purpose as shown in Fig. 2 Ahmedabad is a commercial capital city of the Gujarat state in the western part of India. The origin of Ahmedabad dates back to 1411 when the Nobel Ahmed Shah laid the foundation of the city on the east bank of river Sabarmati.
Jodhpur is the major city of the Marwar region of Rajasthan. Its roots of development are traced back to 1459 when king Jodha of the Rathod dynasty laid the foundation of the city. Both cities were once fortified towns with massive surrounding walls and bastions. In order to enter the city, Jodhpur had seven gateways, while Ahmedabad had twelve gateways safeguarding the city.

Ahmedabad
The vernacular settlement of the old city in Ahmedabad is known as 'Pols'. A pol is a gated community having one entrance where a similar group of people or community lives together. These pols are located on the eastern bank of river Sabarmati inside the walled city of Ahmedabad. The densely packed houses are arranged in a linear manner connecting to narrow streets and squares as shown in Fig. 2.1.1. In response to the situation of conflict between the communities and frequent events of riot, the city of Ahmedabad developed a gated community that ensures security and restricts singular access.

Jodhpur
The spatial organization in the old city of Jodhpur takes into consideration the issues of extreme temperature, solar radiation, glare, sand and dust storms in the development of houses. The houses have flat terraces, open courtyards and projecting balconies with perforated screens. The densely packed houses along the narrow streets breathe through their neighbourhood is formed on the basis of social stratification and occupations, like Brahmins live in Brahmpuri, goldsmiths in Sunaron Ki Ghati, and moneylenders in Bohron Ki Pol. Most of the courthouses are simple with only minimal entrance decoration. Private terraces are a multifunctional social space of the house, which is used for private functions, social interactions, drying the spices and for sleeping during the hot summer nights. In both cities, houses along the main streets have commercial activity on the ground floor with a residential unit above. Both cities have specific local terminology for various parts of the house as described in the table below.   In both settlements, the ambiance is created through the hierarchy of built and open spaces in an unpredictable yet specific order. The spatial arrangement of narrow streets and open spaces, known as "chowk", act as social spaces for celebrations and social gatherings at a neighbourhood level. The "otla" outside the house acts as an interaction space contributing to the character at a micro level. Thus the physical and metaphysical behaviour of the spatial organization plays an important role in creating a lively ambiance.

The spatial organization of study areas
A house is an elementary unit in the spatial organization of a street. The morphology is a result of the interaction of a house with the street and the adjacent spaces at a cluster or neighbourhood level. Their spatial relations have an impact on the level of access and control over each other. The interaction of spaces within the house influences social behaviour. The visibility, permeability, movement and circulation patterns of the activity space within the house determines the social behaviour within the house. The built form of a house is the result of the individual needs and aspirations of each community. These structures reveal the understanding of climate, social structure, usage of locally available building materials, and craftsmanship. The courtyards play a significant role in the spatial organization for providing visibility, connectivity, light and ventilation. Further, the lifestyle adoption of users and multifunctional usage of spaces has greatly influenced building configuration and form. The size of family units, spatial usage, preparation of food, interaction of people and many other cultural considerations also affects the layout and size of dwellings (Rapaport, 1969).
In both case studies, the cluster formation is not following a rigid geometrical pattern allowing the degree of flexibility in spatial organization. The amalgamation of spatial organization and sensorial experiences generates the spirit of the place. This spirit of the space defines the special character of any particular place. In order to understand the ambiance of a place at a varying level from neighbourhood, cluster and house level the analysis of spatial organization plays a pivotal role. The symbiotic relationship of the forms of mass and space in architecture can be examined and found to exist at several scales (Ching, 2007). The detailed understanding of the spatial organization would be created using documented case studies for the city of Ahmedabad and Jodhpur.

Case study selection
The selected area for the study purpose is located in the old fabric of Ahmedabad and Jodhpur as shown in Fig. 3.1.1(a) & (b). Both areas belong to Hindu dominant community having a similar religious background and were built 100 to 200 years ago. The cultural background differs due to the social structure and regional differences. The analysis is done at three levels : 1. Neighbourhood of 200-300 houses 2. Cluster of 6-8 houses 3. Individual dwelling unit The paper examines and analyses the physical spatial organization at various levels to understand the spatial character of a place. It examines important factors that play a vital role in creating a definite spatial organization. Each factor is examined using various analysis methods and derives the constants and variables in both the case studies. It further evaluates the reasons, which are socio-cultural or climatic for the variables that are specific. Fig. 3.1.1 (a) The figure shows the location of the study area in Ahmedabad at three levels City (Ahmedabad) -Area (Khadia) -Neighbourhood (Dhal ni pol) Fig. 3.1.1 (b) The figure shows the location of the study area in Jodhpur at three levels City(Jodhpur) -Area (Brahmpuri)-Neighbourhood (Fatehpol) to the site.

Method for spatial analysis
The space syntax analysis method is used for the purpose of spatial organization analysis. Space syntax tool is simply a way of transforming buildings into dimensionless forms to interpret spatial organization using graphical representation. Along with space syntax, the climatic analysis is done for the available sun hours and shadow patterns in summer and winter months. The analysis is done using a three-dimensional model to examine the results on the building surface as well as on the streets. The analysis generates the graphs and data indicating the behaviour of the space and behaviour of a user at a particular space.

Justified graph analysis
The justified graph is a tool to find out the relationships between the spaces. This method is used for understanding the adjacency of spaces at various scales such as adjacency of streets, clusters, houses and activity spaces within the house. The graph generated shows space as nodes, and line as connected spaces or edges. The dark thick lines in the images represent the main axis and the lighter and thinner lines represent the secondary, as well as the tertiary axis. The bigger dots in the diagram denote the nodes/convex spaces (the spaces between the houses) and the smaller dots denote the houses. The lines indicate the connectivity between the nodes and the houses. The figures below from 3.2.1(a) and (b) show the graphical presentation of Axis and J-Graph analysis at the neighbourhood to house level.

Visibility Graph, Agent movement and isovist analysis
The visibility graph analysis (VGA) is used to check the visibility and permeability as a dynamic component in spatial organization. This analysis will help in the revelation of the hierarchy of spaces from public to private and knowing the locations which remain directly visible or invisible through a colour-coding diagram. The colours from cyan to blue suggest low connectivity, and yellow to red suggest high connectivity. In order to find the natural movement pattern in the building, the Agent's model developed by Alasdair Turner is used for analysis. This helps in understanding the natural path of movement in the way of finding. It also helps in getting insight into private and territorial behaviour. The spatial quality of architectural space can be analyzed using Isovists. The potential field of view from the identified location can be generated using isovists. The depth map creates polygons and helps to measure the depth of each identified location and its relation with each other. A wellintegrated location is colored in red which implies the shallowness, means no turns are required to get from one location to the other. The poor-integrated location is coloured in blue which implies the turns and depth with respect to their locations.

Sunlight hours and Shadow analysis
Sun and wind are the most essential cosmic attributes, as discussed earlier. The sunlight hours analysis is generated using the ladybug component of grasshopper on Rhino. This component calculates the direct sunlight received by any geometry in any given climatic zone. It further helps to understand whether the indoor and outdoor spaces are comfortable to use or not. Both selected cities have a similar climate. The studies are done on both surface and base levels to understand the behaviour of streets and house surfaces with respect to the climate. Low rise and high-density fabric of both the cities have narrow streets, pedestrian pathways and open chowks (open gathering spaces). Instead of such similarities, the study suggests relatively different results for both cities. The graph below shows the indication of hours of sun during the day time. The cold colours from blue to dark red suggest the fewer hours of sunlight where the warm colours from red to yellow suggest more hours of sunlight.

Conclusion
The comparative study of the selected case studies derives the constants and variables of the spatial organization that are responsible for the ambiance of the respective place. The constants are due to the hidden order in its organicness. The variables are due to the specific site conditions and dissimilar social structures. The results of the space syntax analysis and simulations derive the parameters affecting the spatial organization and ambiance generated with that organization. The constants are the result of climate responsiveness in both the settlements. The orientation of the houses promote better daylight and ventilation at the same time protects from the harsh sunlight during the summer season. The street orientation is a response to the existing landform, access and services. Both settlements provide a comfortable temperature in the summer season. The spatial organization of houses in the street responds to accessibility and privacy at the same time. Privacy here is understood both as physical and visual component. The physical component connects or disconnects various levels of accesses at thoroughfare, street or cluster respectively. The visual component is responsible for the sense of safety and connections between people. The city of Ahmedabad shows the character of the planned street as a decisive and conscious effort for achieving privacy. The character becomes more public and inviting at a cluster level. The neighbourhood street is a private entity hence the otla outside the house is the most public space used for interactions. This hierarchy of private to public at neighbourhood to house level generate the lively ambiance within the neighborhood. In Jodhpur, privacy is attained at a house level where the streets are public in nature hence the house edge is the threshold between public and private space. The social structure in Jodhpur necessitates the privacy from the public street. The house orientation and planning encouraged privacy. In both cities, the courtyard is the ultimate source of light and ventilation. This multifunctional space is the center of the house. Both the places have developed their own vernacular vocabulary appropriate for the time and place. The constants in both the case studies are relevent learning for any hot and dry climatic region with a similar background. The variables have more specific learning of the relationship between social behaviour and spatial organization. Altogether, they provide us with a concrete understanding of the vernacular spatial structure and specific ambiance they generate.