The present study aims to investigate the role of transitional space as an intermediary between the entrance of a residential complex and the first residential floor and to examine its contribution to improving the functional performance and efficiency of residential complexes. Furthermore, the study seeks to identify the most effective transitional-space configuration by considering different residential block arrangements. Accordingly, the research addresses the following questions: (1) How can transitional space, as a key component of the physical–spatial structure of residential complexes, improve their functional performance? and (2) Which transitional-space configuration, considering the spatial arrangement of residential blocks, provides the highest level of functional efficiency?
This applied study adopted a mixed-methods (qualitative–quantitative) approach using a descriptive–analytical research design. Transitional space was considered the independent variable, while the functional performance of residential complexes was treated as the dependent variable. Indicators of functional performance were identified through a review of the literature and evaluated using the Space Syntax approach. Spatial configuration was analyzed through pilot-floor graph analysis, Visibility Graph Analysis (VGA), axial analysis, connectivity, mean depth, and isovist measures using Depthmap software. The research focused on medium-scale cooperative housing complexes constructed between 1999 and 2021 in District 2 of Arak, Iran. From 81 residential complexes, 16 met the selection criteria (minimum four stories, at least two residential blocks, diverse shared-space organization, and occupancy status) and were classified according to block arrangement. Two representative case studies were then selected: Jahad Nasr, characterized by a regular block layout, and Andisheh, featuring a mixed block configuration.
The findings demonstrate that transitional space plays a significant role in enhancing the functional performance of residential complexes by improving spatial connectivity, accessibility, visual perception, permeability, spatial legibility, and movement continuity. Space Syntax analyses revealed that residential complexes with well-integrated transitional spaces exhibit more efficient spatial structures, resulting in better circulation patterns and greater opportunities for social interaction among residents. The Visibility Graph Analysis (VGA), axial analysis, connectivity, mean depth, and isovist evaluations consistently indicated that the configuration of transitional spaces directly influences users' ability to navigate and utilize shared spaces effectively. Comparative analysis of the two case studies further showed that the Jahad Nasr residential complex outperformed the Andisheh complex across most spatial performance indicators. This superior performance can be attributed to its more coherent block arrangement and the formation of a well-defined transitional space, which provides stronger spatial integration, higher visual accessibility, and improved continuity between outdoor and semi-public areas. In contrast, the mixed block configuration of Andisheh resulted in weaker spatial integration and reduced functional efficiency.
These results highlight the importance of considering transitional spaces as fundamental design elements rather than residual circulation areas. The study further suggests that the arrangement of residential blocks directly influences the quality and performance of transitional spaces. Integrating Space Syntax analysis into the early stages of residential design can therefore support evidence-based planning decisions and contribute to the creation of more efficient, accessible, and user-centered housing environments.