The Nexus of Morphology and Sustainable Urban Form Parameters as a Common Basis for Evaluating Sustainability in Urban Forms

Abstract

To enhance sustainability in urban design, it is essential to consider urban planning and morphology. This study explores the relationship between key morphological layers and the degree of sustainability in urban forms. Understanding how morphological characteristics influence sustainable urban form parameters provides valuable insights into urban areas’ sustainability potential. Based on this premise, a theoretical model is proposed to assess the potential of urban design for sustainability. The study examines urban forms across multiple scales, from material level to city-wide analysis, employing typo-morphological analysis inspired by Italian and British urban morphology schools. The model has been evaluated by academics from various universities who assessed the relationship between sustainable urban form parameters and morphological elements by weighting their relevance. Analytical tools were applied, including SPSS 29.0 and Excel-based mathematical methods. The results confirm a strong correlation between morphological elements and sustainable urban form characteristics, influenced by scale and classification. Additionally, the study identifies the most impactful parameters for enhancing sustainability in urban design. This research contributes to a comprehensive framework for sustainable urban morphology, offering practical insights for planners and designers in shaping more sustainable cities.

1. Introduction

Sustainability has emerged as an urgent necessity and a prevailing concept in the fields of architecture and urban design [1]. There is a robust connection between urban form and sustainable development [2,3]. However, the intricacies of this relationship are not entirely straightforward, as pointed out in [2], leading urban designers to emphasize morphological factors when pursuing sustainable practices. Accordingly, the idea of assessing sustainability through urban form has gained considerable traction [4,5,6,7].

This research focuses on typo-morphology as a means of evaluating the potential for sustainability in urban design. Typo-morphology considers the hierarchical layers of the city (from materials to the city scale) to establish the significance of specific morphological elements in shaping a sustainable urban environment. By aligning these morphological layers with key sustainable urban form parameters, including efficiency, integrity, responsibility, acceptability, liveliness, and equity [4,5,6,7], this study explores how best to understand and measure urban sustainability (see Section 2 for details).

Hence, our overarching research questions are the following:

• How can the evaluation of sustainable urban forms be carried out through urban morphology?
• To what extent can a typo-morphological approach contribute to assessing sustainability in urban forms?

To clarify these questions further, our aim is to examine the interplay between micro-scale elements (e.g., construction materials, building layouts) and macro-scale components (e.g., street networks, neighborhood patterns) in determining overall sustainability. By aligning these morphology layers with well-established sustainability parameters (including efficiency, integrity, responsibility, acceptability, liveliness, and equity), the research endeavors to reveal how each typological element of an urban area can either enhance or diminish its long-term viability. This perspective ensures that researchers and practitioners can pinpoint precisely which urban-form scale most strongly impacts sustainability goals, thereby answering the questions of ‘how’ and ‘to what extent’.

Accordingly, we have developed a coherent morphological framework for assessing sustainability, which synthesizes ideas from Conzen’s and Caniggia and Maffei’s taxonomies and integrates them with sustainable urban form parameters identified in the literature. We tested this framework through surveys and statistical analyses (see Section 3), then validated the consistency of the findings using ANOVA tests (see Section 4).

After collecting expert assessments across multiple scales, the study computed numerical scores to highlight which morphological elements (for example, plot, building, and city) scored highest in relevance to sustainability criteria. The study then presented subsequent statistical tests (such as ANOVA) in tables and figures to clarify the significance of these scores and verify that the panelists’ evaluations were broadly consistent. For further clarity, we also included visual representations, such as plots showing the distribution of expert scores, so that readers can discern how certain parameters (like acceptability and efficiency) consistently emerged as leading factors. By combining descriptive statistics with inferential testing, the results section underscores not simply the raw numerical findings but also the broader patterns that tie morphological characteristics to sustainability goals.

The novelty of this paper lies in its development of a comprehensive, theoretically grounded model that integrates typo-morphological classification with the parameters of sustainable urban form, thereby offering an innovative framework for evaluating urban sustainability. By synthesizing Conzen’s and Caniggia and Maffei’s frameworks of typo-morphological layers with Kropf’s hierarchy of built forms and aligning this structure with clearly defined sustainable urban form parameters, the study derives a methodologically rigorous approach that bridges theoretical urban design with practical assessment tools. Furthermore, the integration of hierarchical morphological layers, assessed through empirical analysis with input from academics and urban professionals using statistical techniques, such as ANOVA, adds further depth and validation to the model. This methodological framework represents a significant advancement in the field, offering a robust framework for assessing sustainability across multiple urban scales, from material to city level.

2. Literature Review

2.1. Urban Morphology

Morphologists and urban designers concentrate on the tangible or material aspect of urban spaces, with urban elements serving as their shared connection or framework [8]. Urban morphologists analyze and categorize urban elements based on their characteristics, while urban designers typically employ a range of urban elements to craft three-dimensional urban environments. Additionally, the literature review delves into the concept of tools for classifying urban morphology. Through this tool, an attempt is made to explore an approach suitable for assessing sustainability in urban form using the parameters associated with sustainable urban development.

The examination of the structures and arrangements of the constructed environment in human settlements is referred to as urban morphology [9]. It serves as a method for comprehending the intricate and diverse settings of human settlements. Urban morphology involves scrutinizing the physical built form of urban areas, identifying key individual elements, and understanding their spatial arrangement [10]. Simply put, “urban morphology” can be defined as the study of spatial form [11]. Urban morphology recognizes that the physical form of a city undergoes changes over time and views the city as a dynamic process rather than a static object [6]. This approach is particularly applicable to research and practices focused on the environmental, economic, and social aspects of urban form [12].

2.2. Typo-Morphology

The term ‘Typology’ first surfaced in architecture during the 19th century, referring to a study of types closely linked to the comparative analysis and classification of structural or other characteristics into specified categories [13]. Within this understanding, ‘Type’ can be construed as a model or pattern that signifies something and carries symbolic meaning or signification [14]. In urban design, a ‘Type’ is recognized as a specific set of form properties for buildings, spaces, or the synthesis of both groups. Reference [15] emphasized the modification of the concept of type and typology to dissect the urban fabric, viewing the architectural object not as an isolated and single type but as possessing the juxtaposition of memory and causes, determined as an urban artifact [16]. This study, therefore, delves into the underlying concepts of a typo-morphological approach to assessing sustainability in urbanism. Typo-morphology serves as a means to comprehend cities and their evolution in urban morphology by categorizing urban elements into types [17]. It encompasses the typology of buildings and spaces, as well as the urban forms of buildings and spaces. Typo-morphology considers the city at different scales, ranging from the material to the large street pattern, viewing the urban area as dynamic rather than fixed [6]. The concept of the typological approach originated with Saverio Muratori (1910–1973), who based the analysis on a systematic understanding of the history of cities, encapsulated in the concept of “operative history” [18]. This approach allows for understanding the growth of the city pattern as a living organism, demonstrating the spatial and physical structure using essential notions of type, texture, organism, and region to formulate urban form typologies specific to a particular city [19].

In the other study, ref. [20] specified a methodology considered as a typological process to discern changing conditions in urban form along with its historical development based on its component types and their evolution. Muratori and Caniggia discussed the typology of the building through the foundation of practical typologies [6]. Practical typologies encompass gradual transformations of the building’s idea in its relation to the route. Caniggia characterizes two key urban elements in interaction: the route and the building. The city block is commonly defined by the character of the route and aligned buildings and portions [21]. These processes occur sequentially, from the building (architectural scale), block, or gathering of blocks in a matrix shape (urban scale) to settlement arrangement along the regional poles and the matrix axes (regional scale). Therefore, typo-morphology comprises building typologies on lots, streets, blocks, and poles hierarchy and routes [20].

2.3. Classification and Basic Units of Typo-Morphological Description

The research presented in [22] identified three key themes crucial to a robust research agenda in urban morphology: establishing connections between structure and process, defining the fundamental units of morphological characterization, and delineating spatial relationships consistent with the implicit geometry of the urban area. Consequently, the development of a classification framework for the fundamental units in morphological description stands out as a paramount factor in urban morphology. This involves an understanding of the physical scales at which the urban area can be assessed.

The research of the Italian school of urban morphology, particularly by Caniggia and Maffei, introduces two perspectives on urban morphology: temporal and spatial. This is also known as co-presence or derivation, wherein the urban area takes shape on multiple scales simultaneously while being subject to change over time, crystallizing its form based on past events [23]. Caniggia’s conception of the city relies on the fitting of objects (materials, rooms, buildings) into each other at various scales, employing a modular principle where understanding any scale necessitates comprehension of the scales below and above [24]. Accordingly, he devised a hierarchical concept for the urban area comprising four levels: elements, structures, systems, and organisms [10,20]. These four scales are explained as buildings, groups of buildings, the city, and a region [6]. Caniggia’s spatial arrangement is based on elements, element structures, structures systems, and systems organisms. As shown in the Figure 1, this hierarchy is independently applied to buildings and towns, and the object of the smallest scale depends on the scale of the study area.

Kropf, along with other urban morphologists, has compiled a hierarchy of scales, including elements such as materials (tiles, bricks, timber) forming structures like slabs, walls, and basements. These structures, in turn, shape rooms, inner spaces, corridors, stories, etc., ultimately culminating in the creation of entire buildings [10]. The diagram presented in Figure 2 is utilized to extend this hierarchy upwards by considering a building as the element and defining additional levels, such as urban tissue, district, and town [24].

The contributions of the British school of urban morphology, specifically the research of Conzen [9], are prominently characterized by the development of a hierarchical structure known as ‘town-plan analysis’. Conzen’s approach is explicit in formulating this structure, focusing on key factors for analysis, including the town plan, pattern of building forms, and pattern of land use. According to Conzen, the fundamental elements of the town plan encompass three levels or layers: building patterns, plot patterns, and street patterns [10]. Street patterns involve streets and their organization into a street system; plot patterns consist of plots (or lots) and their arrangement into street blocks; and building patterns include buildings in the form of block plans [25]. Additional elements within this framework include the lot (equivalent to Conzen’s “plot”), the route or street, and the relevant strip (created by lots encountering a route) [26].

Kropf utilizes Conzen’s plot as a reference point and explicitly incorporates into his framework the building and the layers described by Caniggia beneath the building—rooms, structures, and materials. The substructure is defined as filling the space between initial levels, with windows between materials and structures, and floors serving as intermediate levels between rooms and buildings [26]. Consequently, Kropf’s comprehensive framework of hierarchical levels comprises materials, structures, rooms, buildings, plots, streets, and the urban tissue (

Table 1. Interpretation of Kropf’s taxonomy of built forms (developed by the authors).

Material	Bricks, slabs, beams, concrete, construction materials.	Micro
Structure	Masonry walls, timber walls, assembly of roofs.
Room	Encompassing lift walls, corridors, and stairway.
Building	Raw house, semi-detached, detached buildings, commercial buildings, etc.
Plot	Cadastral zone with one or more than one building.
Street	Involving groups of plats, squares, and city blocks.
City	Town or city.	Macro

). Kropf proposes this hierarchy as a ‘critical tool’ for assessing the diversity of urban and built forms, providing more precise explanations and achieving better outcomes during the participation in its formation or transformation process [24].

This final aspect holds significance in enhancing outcomes during the development of urban areas, rendering morphological analysis a valuable tool for assessment when aligned with the principles of sustainable urban forms. Sanders and Woodward [27] have illustrated the utilization of urban morphological analysis to deconstruct the urban area into its fundamental components at various scales (layers or levels) and leverage this analysis to evaluate the city as a whole. Consequently, the integration of typo-morphological traditions with the British school of urban morphology, particularly Conzen, and the Italian school of urban morphology of Caniggia and Maffei [20], is synthesized through Kropf’s taxonomy, forming a tool for appraising sustainability in urban forms.

2.4. Sustainable Urban Form and Its Parameters

A sustainable urban area is perceived as a region that achieves enduring physical, social, and economic development while maintaining continuous access to natural resources within sustainable limits and ensuring ongoing resilience against environmental threats [28]. Various theoretical models have been proposed to conceptualize sustainable urban areas: (1) compact, high-density urban form [29], (2) low-density decentralized urban areas [30], (3) decentralized concentration, and (4) models influenced by Howard’s Garden City [31]. In each approach, the core is a balance of environmental, social, and economic factors [32].

From a broader review, six fundamental parameters—efficiency, integrity, responsibility, acceptability, liveliness, and equity—are identified as primary contributors to a sustainable urban form [33,34,35]. Briefly, the parameters are as follows:

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Efficiency: Optimizes energy consumption in buildings and transportation systems [33,34,35,36,37,38,39].

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Integrity: Maintains compositional and historical coherence, preserving social and visual harmony [33,40,41,42,43,44].

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Responsibility: Safeguards resources, lowers pollution, and integrates advanced technologies to minimize environmental impact [45,46].

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Acceptability: Improves quality of life by ensuring social interaction, sense of place, safety, and overall satisfaction [47,48,49,50,51,52,53,54].

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Liveliness: Encompasses ecological diversity, social interaction, and vibrancy in the urban environment [55,56,57,58,59,60,61,62,63].

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Equity: Addresses access to resources, affordability, and job opportunities [7,59,64,65,66,67,68,69,70,71,72].

Within this study, these parameters serve as the main criteria for evaluating sustainability via the typo-morphological framework described earlier. In the following sections (Section 3 and Section 4), we illustrate how each parameter interacts with a particular morphological layer, ranging from material to city, and provide a statistical validation of the approach.

2.4.1. Efficiency

Efficiency involves optimizing energy consumption, whether through building retrofitting or transportation systems [36,37]. It is a crucial parameter widely discussed by researchers, forming a significant aspect of the sustainable urban form discourse [35,38]. Energy efficiency in various urban forms has been extensively examined in different research studies [33,35,39]. The building sector and transportation are identified as primary contributors to energy consumption. Energy consumption in the building sector occurs through two distinct paths: energy capital, involving energy used in constructing buildings and infrastructure in urban areas, and energy revenue, which refers to energy consumed during a building’s lifespan [37]. Consequently, this study delves into the critical factors influencing the efficiency of urban form, including building materials and design, transportation systems, and maintenance of the built environment.

2.4.2. Integrity

Integrity pertains to the coherence of components and the character of the urban area [33,40]. In urbanism, integrity manifests through three primary aspects: visual integrity or compositional features, historical-structural integrity, and socio-functional integrity [41]. Visual integrity or compositional features are linked to the urban area’s texture, visual harmony of landscapes and buildings, and relationships among building units and urban texture [42]. This aspect supports and sustains a balanced and integrated environmental ecosystem [43]. Additionally, it determines the historical performance of the design, considering the age of construction, which can provide indicators about embodied energy, cost, and the authenticity of the urban fabric, influencing the social aspect of sustainability [44].

2.4.3. Responsibility

Responsibility involves safeguarding resources and reducing pollution [45]. In the realm of urban sustainability, the significance of ‘Responsibility’ lies in enhancing productivity and innovation, minimizing costs, and mitigating environmental impact while providing opportunities for residents to adopt a sustainable lifestyle. Indicators of responsibility span technical, social, and institutional domains [46]. Technical indicators encompass the adoption of new technologies and sustainable practices in sectors such as energy generation, waste management, transport, and water. Social indicators relate to values, norms, and social practices or behaviors. Institutional indicators cover waste management, water management, energy consumption, as well as the assessment of greenhouse gas (GHG) emissions and urban environmental performance, aiming to establish clear targets for mitigating resource depletion.

2.4.4. Acceptability

Acceptability is tied to the well-being and quality of life. It encompasses various factors, including the following:

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Pride or sense of place: This considers the community’s sense and is linked to social order, participatory norms, and the culture of the community, including interactions with neighboring areas [47]. It involves a shared belief among members that their needs will be met through their commitment to community cohesiveness [48]. This aspect strongly correlates with the physical aspects of the built environment and structures, influencing social interactions with these physical elements and thereby enhancing social sustainability through its impact on people’s satisfaction.

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Social interaction within the community: The established connections between urban structure and social communication and systems are crucial for improving social sustainability. This involves social associations, including trust and the strength of connections within systems and commitments to shared aspirations [49].

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Safety: This parameter is a fundamental element in Maslow’s hierarchy of needs [50] and is integral to social sustainability [51]. It relates to improving building materials, stable structures, and safe design [52]. Feeling secure and safe contributes to social sustainability. Living in a safe neighborhood, where there are no fears from neighbors, has been identified as a preference [53]. The sense of safety enhances trust, reciprocity between neighbors, and fosters a strong sense of place in a community.

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Satisfaction: Satisfaction addresses basic needs and resource access. On an individual level, it aligns with Maslow’s hierarchy of needs, encompassing physiological needs like health, water, food, and safety. On a social level, it involves relationships, reciprocal respect, and confidence, while on the self-actualization level for both individuals and society, it includes morality and creativity [54].

2.4.5. Liveliness

Lynch identifies liveliness as one of the seven pillars determining a city’s quality. He posits that the fundamental elements of functional liveliness encompass survival, safety, and compatibility [55,57]. Liveliness establishes a connection between ecology and society by exploring the relationship between inhabitants and their environment, emphasizing diversity and interactions [56,59]. On the ecological level, liveliness relates to design variety, incorporating changes, a sense of place, architectural distinctions, street lighting quality, security levels, and the eco-friendliness of the urban environment. The social dimension involves the interaction of individuals within the community, contributing to the vitality of the surroundings through the activities of people in that environment [55,60]. As it is mentioned, urban networks encapsulate key characteristics of urban planning and socio-economic activity, fostering social dimension, connectivity, and social interaction core elements that improve liveliness within a sustainable urban form [61,62,63].

2.4.6. Equity

Equity is understood as the fare distribution of resources, fair access to basic needs and services, and finally, inclusive participation [7,64,65,66,67,68,69]. Equity deals with the essential local services such as supermarkets, schools, and health centers; leisure opportunities and open spaces; public transport; employment opportunities; and affordable residency [67,68,69,70,71,72]. Rapid urbanization has, however, exceeded the capacity of countries to provide sufficient infrastructure, while increased job insecurity in cities leads to further rises in social and economic inequities [7,59,65,71,72]. The big burden of the recent global economic downturn has contributed to unemployment and work losses, contributing in turn to reduced healthcare and increased social problems. Figure 3, shows the parameters of sustainable urban form with their indicators as obtained based on the literature review.

The parameters of sustainable urban form are categorized according to the environmental, social, and economic characteristics within the scope of this study. These parameters serve as the primary overarching objectives for assessing sustainability in the urban area, utilizing the typo-morphology classification for urban forms. The structure of any classification system outlines the purpose of the classification, encompassing its fundamental elements of description. Various frameworks exist for describing and classifying urban forms [57,70]. The methodology employed in this study, as illustrated by a representative example in the subsequent section, is centered on the classification and correlation of parameters and rules of sustainable urban forms with the framework of morphological layers.

3. Representative Instance

3.1. Methodology

In this instance, the assessment of sustainability in urban form is conducted through the typo-morphology methodology, establishing a connection between the parameters of sustainability in urban forms and the fundamental elements of typo-morphology. Thus, the amalgamation of Conzen’s and Caniggia and Maffei’s schematics of typo-morphological layers [9,20] with Kropf’s comprehensive hierarchy of form results in hierarchical relationships among elements of the built form [23], forming the basis for a general morphological classification system. This encompasses materials, structure, rooms, buildings, plots, streets, and the city. Simultaneously, the fundamental parameters and their indicators for creating sustainable urban forms, as identified through a literature review, will be established to facilitate research and practice in urban sustainability. These parameters include efficiency, integrity, responsibility, acceptability, liveliness, and equity, each having several indicators. The study’s hypotheses focus on the assumption that a strong correlation exists between hierarchical morphological units (e.g., from material to city scale) and measurable indicators of sustainability (e.g., resource efficiency, social interaction, equitable access). Specifically, our central hypothesis is that each morphological level exerts a distinct but interconnected influence on sustainability outcomes, such that higher-level systems (like street networks or entire city districts) magnify or moderate the effects originating from lower levels (such as building materials or interior configurations). By statistically testing expert evaluations (through methods including descriptive analyses, ANOVA, and regression models), the study hypothesized that certain parameters, particularly efficiency and acceptability, would emerge as more impactful in shaping a robust, sustainable urban environment. The results confirmed and refined this initial assumption by demonstrating how morphological scales interact differentially with key sustainability parameters. Therefore, this research developed a methodological toolkit to evaluate the built environment while providing a framework to facilitate the complex relationships between the physical form of the urban environment and its performance to inform the design and development of more sustainable urban forms. Through a typo-morphological approach rooted in the theories of Conzen, Caniggia, Maffei, and Kropf, the study links hierarchical layers of urban form from materials to the city scale with six key sustainability parameters. Expert evaluations were collected and analyzed using statistical methods, including ANOVA and regression, to validate the structure and identify the morphological elements most influential in shaping urban sustainability.

As presented in Figure 4, this study lies in its structured three-stage approach, integrating urban morphology and sustainable urban form through a comprehensive methodological framework. In the first stage, the study introduces key urban morphology approaches, particularly the typo-morphological perspective, and develops a classification framework grounded in scale hierarchy theory, serving as the input phase. The second stage addresses the concept of sustainable urban form parameters, contributing analytical tools to assess built environments from a sustainability perspective when considering the morphology of a city. Finally, the third stage synthesizes these findings through an integrated methodology, enabling the development and evaluation of a toolkit that reveals the evaluation of sustainability based on the relevance of the sustainable urban form parameters within typo-morphological hierarchical levels, constituting the output phase of the research.

This framework offers a means to examine the sustainable urban form of any city. The utilization of this model relies on indicators that serve as tools or criteria for assessing sustainability.

3.2. Analytical Tools

A methodology was devised to evaluate the integration of various indicators pertinent to sustainable urban form parameters with typo-morphological elements, grounded in a classification framework spanning multiple scales including the city level [49,73,74,75]. In accordance with this framework, a checklist was prepared using the proposed indicators. To validate the coherence of the morphological framework for sustainability assessment and to bolster sustainable urban design, a group of academics and professionals was consulted.

The assessment process entailed examining the relevance of the sustainable urban form parameters within the typological classification elements via conventional mathematical methods. Each indicator’s relevance was categorized into three levels, each denoted by a specific numerical value. For instance, within the typo-morphological classification framework, professionals judged the integration of the ‘material’ element with ‘building material’, one of the indicators of ‘Efficiency’ based on its perceived importance. The results were classified as (1) for very relevant, (0.5) for relevant, and (0) for not relevant (see

Table 2. A sample of the ‘Checklist’ for the evaluation of sustainability based on the relevance of the sustainable urban form parameters within typo-morphological hierarchical levels (developed by the authors).

Typo-Morphology Framework		Material	Structure	Room	Building	Plot	Street	City	Scores of Each Indicator	Scores for Each Parameter
Sustainable Urban Form Parameters
Efficiency	Building Material	1	1	1	0.5	0.5	1	1	6	19
	Building Design	1	1	0.5	1	1	0.5	1	6
	Transportation System	0	0	0	0.5	1	1	1	3.5
	Building Maintenance	0.5	0.5	1	1	0	0	0.5	3.5
Integrity	Visual Integrity	0.5	0.5	1	1	1	1	1	6	16
	Structural Integrity	0.5	1	0.5	1	1	1	1	6
	Functional Integrity	0	0	0.5	0.5	1	1	1	4
Responsibility	Technical	0.5	0.5	0.5	0.5	1	1	1	5	13
	Social	0	0	0	0.5	1	1	1	3.5
	Institutional	0.5	0.5	0.5	0.5	0.5	1	1	4.5
Acceptability	Pride/sense of Place	1	0.5	0	1	1	1	1	5.5	19.5
	Interaction with Group	0	0	0	0.5	1	1	1	3.5
	Safety	0.5	0.5	0.5	1	1	1	1	5.5
	Satisfaction and Stability	0	0.5	0.5	1	1	1	1	5
Liveliness	Ecological	0.5	0.5	0.5	1	1	1	1	5.5	10
	Social	0	0	0.5	1	1	1	1	4.5
Equity	Public Transport	0	0	0	0.5	0.5	1	1	3	13
	Job Opportunities	0	0	0	0.5	0.5	0.5	0.5	2
	Affordable Housing	0.5	0.5	0.5	1	0.5	0	1	4
	Access to Services	0	0	0	1	1	1	1	4
TOTAL SCORES		7	7.5	8	15.5	16.5	17	19

).

Moreover, the weighting exercise (see Table 2) was performed by a panel of 35 experts comprising architects, urban planners, and engineers who contributed a diverse set of perspectives on what drives ‘Efficiency’ in urban form. The experts assigned numerical values (1 for ‘very relevant’, 0.5 for ‘relevant’, and 0 for ‘not relevant’) to each indicator across the different morphological layers. Once statistically processed, “building material” emerged as consistently high ranking, due to its clear impact on operational and embodied energy costs at the city scale. Although transportation systems also received considerable weight, many experts noted that transport outcomes are often influenced by policy-level decisions (for example, enhancements to public transport) or large-scale infrastructure investments beyond the direct control of smaller-scale design interventions. Consequently, this multi-tiered scoring approach helped illustrate how each indicator’s relevance can vary depending on whether it is applied at the micro (material) scale or the macro (city) scale. This clarifies why “building material” can sometimes surpass “transportation system” in the aggregated ‘Efficiency’ scores.

In order to further elucidate the rationale behind both the selection and weighting of indicators under each sustainable urban form parameter, we expanded our discussion of the assessment methodology (see Section 3.2). The initial suite of indicators such as building material, transportation system, maintenance, and building design within the “Efficiency” category was derived from an extensive review of the literature addressing principal drivers of energy consumption and resource utilization. Building material, for example, received a higher score in the ‘Efficiency’ column because it exerts a direct and enduring influence on a building’s overall energy performance. Materials with superior insulation properties can dramatically reduce energy demand over the building’s entire lifespan, and the embodied energy from extraction or manufacture to installation can be notably high.

By contrast, although the “transportation system” indicator exerts a substantial effect on energy use, its efficiency often depends partly on broader infrastructural or policy factors that fall outside the immediate remit of a single urban project. This consideration explains why, during the expert weighting process, building material frequently attained a marginally higher and more direct impact within the ‘Efficiency’ dimension.

Higher scores assigned to the parameters indicate a greater level of interaction and impact of their indicators on sustainability assessment within the morphological framework for evaluating sustainability in urban form [76]. Similarly, elevated scores for morphological elements at different scales signify the significance of the morphological element within that scale for assessing sustainability in urban form. In adherence to a relational survey style, where the study recommends a sample size of not less than 30 [77,78,79,80,81], a group of 35 experts in the field was selected to initiate the assessment process. Descriptive statistical methods were employed to analyze the data obtained from the checklist. The application of the ANOVA technique aims to determine the significance of survey or test results [79,80]. One-way ANOVA, a widely applicable method for analyzing differences between the means of more than two groups, was employed to compare the results of each assessment. This helped in understanding the consistency in the responses across each checklist and validating the obtained results [81,82,83].

4. Analysis and Findings

Finally, a total of 34 assessments were received; however, due to incomplete responses, 32 answers were considered usable. The assessment results indicate a consensus among participants regarding the relevance and interaction of typo-morphology classification framework units and sustainable urban form parameters [84]. To ascertain the validity and confidence level of the assessment, a one-way ANOVA test was conducted. The SPSS analytical tool was employed for performing one-way ANOVA on the 32 assessment responses from participants. In the context of a one-way ANOVA test with a 95% confidence level, the alpha level value was set at p = 0.05. The hypothesis tested whether the participants’ assessments were similar, supporting validity, or if there were differences. The one-way ANOVA results for assessments of typo-morphology units at various scales, ranging from material to territories or the city, are detailed below.

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The degrees of freedom (DF), both between the groups and within the groups, were calculated to determine the ‘F-critical’ value. The DF between the groups was found to be 31, and the DF within the groups was 192, resulting in a total DF of 223. Utilizing these key values, the ‘F-critical’ value was determined to be 1.511, obtained either from tables or through calculation.

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The sum of squares (SS) was computed, encompassing SS total, SS within, and SS between, yielding values of 4727.35, 4584.64, and 141.71, respectively.

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Variance between and within the groups was determined by calculating the mean square (MS) between and within. The mean squares were derived from the sum of squares and the degrees of freedom between and within the groups. Consequently, the MS between groups was calculated to be 4.57, while the MS within groups was determined to be 23.88.

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Based on the foregoing results, the F-value was calculated using MS between and MS within, resulting in an F-value of 0.192.

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Comparing the ‘F critical’ value of 1.511 with the calculated F-value of 0.192, it is evident that the assessment results and the answers from the 32 participants are similar and not in the critical region. This is because the F-critical value (1.511) exceeds the calculated F-value (0.192). Therefore, the one-way ANOVA results indicate the failure to reject the hypothesis of similarity in the answers or assessments of the academicians regarding the influence of each unit in the typo-morphological classification on sustainability in urban form.

Thus, the findings emphasize the significance of the typo-morphological units’ scale, ranging from the micro scale (materials, structure, rooms, etc.) to the macro scale (plot, streets, city). The importance of these units and their impact on assessing sustainability in urban form increases concerning their connection with sustainable urban form parameters. The relevance between the indicators of sustainable urban form parameters and the material (micro scale) commonly received scores between 6 and 10. However, at the city layer (macro scale), it scored between 18 and 20. This underscores the importance for decision makers to carefully select the morphological layer for evaluating sustainability in urban form based on the scale of the specific case study area.

The same methodology was applied to evaluate the influence of sustainable urban form parameters on assessing sustainability in urban areas [85]. The process involved testing the responses of the 32 participants to determine the similarity in their answers and the validation of the assessments. Subsequently, one-way ANOVA was employed to assess the validity of the responses regarding the effects of the six parameters of sustainable urban forms, along with their indicators. The results of the one-way ANOVA test indicate a strong similarity in the assessment of the parameters and indicators of sustainable urban forms when integrated with the typo-morphology classification framework, as outlined below:

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The degrees of freedom (DF) between the groups was 31 and within the groups was 160, resulting in a total DF of 191. The ‘F-critical’ value was determined to be 1.52. The sum of squares (SS) total, SS within, and SS between were found to be 2732.03, 2580.54, and 151.49, respectively. Additionally, the MS between was calculated as 4.89, and the MS within was 16.13. Consequently, the calculated F-value based on the above results was 0.30.

Based on the information provided, the results of the one-way ANOVA test indicate that there is no basis to reject the hypothesis of similarity in participants’ assessments regarding the impact of parameters and indicators. This is evident from the fact that the calculated F-value is smaller than the F-critical-value, signifying that the assessments fall outside the critical region. Therefore, the assessments can be deemed valid, and participants’ responses are consistent.

Indicators play a crucial role due to their multiple features: (1) They serve as a guide in setting and measuring targets for success, (2) act as a feedback tool for achieving expected results, and (3) help identify weaknesses in design functioning, thereby enhancing the decision-making process. Higher scores collected by parameters and indicators indicate a more significant impact on evaluating sustainability in urban forms. The assessment reveals that parameters such as acceptability and efficiency consistently receive higher scores, with acceptability often surpassing 20 and efficiency ranking as the second highest parameter after acceptability. On the other hand, ‘Responsibility’ and ‘Integrity’ constitute the second tier in score collection, while ‘Liveliness’ and ‘Equity’ consistently rank lower (mostly below 20 scores). Higher scores denote a more substantial influence on sustainability in urban forms.

In summary, the first priority among sustainable urban form parameters affecting the evaluation of sustainability is given to acceptability and efficiency. The subsequent impact is attributed to integrity and responsibility. In contrast, liveliness and equity form the third group of parameters, exerting a lower influence compared to the first two groups. In fact, the findings of this part of the study provide valuable insights for decision makers in understanding the indicators that influence the evaluation of sustainability in urban forms based on the proposed theoretical model. Such results can inform strategies related to the development of sustainable urban design. In addition to the previous statistical analysis in SPSS, regression analysis was adopted to unravel the intricate relationship between key morphological elements and the degree of sustainability within urban forms. The results of this analysis are presented in Figure 5a–g, linked to the morphological elements, material, structure, room, building, plot, street, and city, respectively. In fact, the range of total scores assigned by academicians to morphological elements offers a nuanced understanding of perceived sustainability. According to Figure 5a, the “Material” element demonstrates a range from 5 to 9.5, indicating varying opinions on its sustainability contribution. In contrast, the “Structure” element spans from 6.5 to 12, with a more considerable spread (Figure 5b), emphasizing the diverse perspectives on structural sustainability. The “Room” element, with scores ranging from 8 to 12.5, reflects nuanced evaluations, while the building element displays a substantial range of 12 to 17, signifying differing perceptions on the sustainability of built structures (Figure 5c). According to Figure 5d–f, the “Plot”, “Street”, and “City” elements present ranges of 15 to 19, 16.5 to 20, and 18 to 20, respectively, revealing intricate dynamics in the evaluation of sustainability at broader urban scales.

Complementing the total scores, the derived R-squared values offer a statistical lens through which the correlation between sustainable urban forms parameters and morphological elements can be interpreted. The “Structure” and “Room” elements emerge as the most influential, boasting R-squared values of 0.4952 and 0.5097, respectively, indicating a robust correlation with the overarching sustainability framework. These elements signify key components in shaping sustainable urban forms, deserving heightened attention in urban planning and design.

Conversely, the “Building” and “City” elements exhibit lower R-squared values of 0.0187 and 0.0601, respectively, suggesting a weaker association with the sustainability framework. The intricacies involved in understanding the sustainability of built structures and entire urban ecosystems necessitate further exploration [79]. The “Material”, “Plot”, and “Street” elements exhibit varying levels of correlation, with R-squared values of 0.3432, 0.1431, and 0.1283, respectively. While the correlation for the “Material” element can be considered moderate, the relatively low R-squared values for “Plot” and “Street” suggest weak linear relationships. Although not statistically significant, these findings may still offer preliminary insights, indicating the need for deeper investigation into potential nonlinear patterns or contextual dependencies influencing these elements. Figure 5h visually depicts the dataset distribution presented in Figure 5a–g, offering a summary of key statistical measures such as the minimum, first quartile, median, third quartile, and maximum values, all associated with the elements under study.

Overall, the findings reveal that the parameters such as acceptability and efficiency hold particularly strong relationships with morphological layers across diverse scales, thereby suggesting targeted strategies ranging from improved building materials at the micro scale to enhanced public transport options at the macro scale. The discussion interprets these statistically significant results by connecting them to earlier scholarships on typological analysis and by highlighting the real-world relevance for urban designers, planners, and policymakers. The intention is to demonstrate how the study’s approach can serve not merely as a diagnostic tool but as a roadmap for prioritizing sustainability interventions at the appropriate level of urban form

Looking ahead, the model’s integration of typo-morphology with sustainability parameters can be broadened to encompass a range of social and organizational dimensions. For instance, at a social level, these findings can inform community engagement processes by identifying which physical elements best foster cohesion, safety, and a sense of place. In corporate and managerial contexts, firms could apply the model to gauge the long-term operational viability of proposed developments, ensuring that efficiency measures, resource stewardship, and equitable access align with organizational goals. Similarly, public institutions could refine governance and policy frameworks, using the study’s evidence to draft planning guidelines that encourage morphological patterns conducive to sustainable growth. Ultimately, future research could expand the methodological toolkit (e.g., adding life-cycle cost analyses or stakeholder surveys) to capture the financial and managerial implications of design decisions, thereby enhancing the model’s value for both private and public sector stakeholders.

5. Conclusions

Understanding the way of assessing sustainability in urban form has the potential to significantly reduce the environmental impact in urban areas and achieve sustainability. Therefore, this study has explored the relationship between the typo-morphological scales, the parameters, and the indicators of sustainable urban form. Thus, on the one hand, the assembly of Conzen’s and Caniggia and Maffei’s schematics of typo-morphological layers along with the Kropf hierarchy of form into the hierarchical relation among elements of the built form has established the structure of a morphological classification system. It includes materials, structure, rooms, buildings, plots, streets, and city. On the other hand, the parameters and their indicators for creating sustainable urban forms have been formulated according to the review of the state-of-the-art to enable the assessment of urban sustainability research and practice. These parameters are efficiency, integrity, responsibility, acceptability, liveliness, and equity, where each of these parameters has its measurable indicator. Accordingly, the study synthesizes these two important bodies to propose a consistent morphological structure or model for urban sustainability assessment, as seen in Figure 4. Thus, it has answered the first question “How can sustainable urban form be evaluated by urban morphology?” By the assessment of the proposed model through developing a checklist to be evaluated by a sample of academicians and professionals to answer the second question, which is “To which extent can typo-morphology and sustainable urban form assess sustainability in urban form?”, the results showed the following.

Firstly, there is a significant similarity in the assessment of the parameters and indicators of sustainable urban forms when interacted with the typo-morphology classification framework, where the role of the scale of the typo-morphological units has shown that the relevance and the effects of the units is increasing in terms of the relationship with sustainable urban form parameters. Hence, the decision makers should have awareness about the morphological scale to assess sustainability in urban forms. Secondly, regarding the parameters of sustainable urban forms, the effects of these parameters according to their scores (higher scores mean greater effects on the sustainability) have shown that the parameters that most affect the assessment of sustainable urban form are acceptability and efficiency. The next are integrity and responsibility, while the third group of parameters that affect the evaluation of sustainability with lower scores than the previous two groups are liveliness and equity. These results will enable us to understand the indicators that influence urban sustainability assessment on the basis of the theoretical model proposed. Finally, these findings will be useful for the relevant techniques for sustainable urban design. This research offers an approach to the sustainable urban form of any city.

6. Limitations and Further Research

While the findings showed a broad consensus among the 32 participants whose responses were deemed complete and valid, we recognized that excluding three incomplete submissions could introduce a mild sample bias. It is possible that those incomplete questionnaires may have represented different viewpoints, potentially influencing the final assessment outcome. Furthermore, although the one-way ANOVA indicated that the existing 32 responses were sufficiently consistent for meaningful results, we acknowledge that a higher response rate or additional participants from a variety of professional backgrounds could strengthen the robustness of the conclusions. Therefore, future research should consider recruiting a larger and more diverse sample, possibly expanding beyond local academic circles to include practitioners and stakeholders from multiple regions.

Moreover, the city samples and expert panels in our study leaned strongly towards European and Mediterranean contexts. While the core concept of applying typo-morphological frameworks and sustainability indicators can be adapted to most urban settings, the specific weighting of indicators might vary in non-European or rapidly urbanizing regions, where climatic conditions, cultural factors, or policy frameworks differ considerably. To address this limitation, subsequent studies could include case studies from diverse geographic areas to ascertain how well the proposed methodology translates to different climates, cultural practices, and regulatory environments. Incorporating these contexts will help refine the weighting system further, ensuring that parameters such as social equity, liveliness, and local building materials reflect the conditions of each region. By expanding both the sample size and regional scope, the proposed framework can evolve into a more universally applicable tool for assessing and guiding sustainable urban design.