This research aims to explore the application of timber lattice systems on roofs in Cairo, Egypt. Before delving into the project itself, a thorough review of relevant references was essential for a better understanding of the system. The building analyzed was the Sunny Hills Cake Shop, designed by Kengo Kuma and Associates. Characterized by a visually striking 60x60mm member lattice structure, the components were locally sourced from indigenous timber and handcrafted by the local labor. However, this architectural piece was not immune to criticism, particularly for the excessive use of material. Consequently, Sunny Hills served as an instructive anti-example, prompting a shift away from a mere emphasis on aesthetics to a focus on optimization. Our approach was instead based on a notable research project at the University of Pennsylvania. This research, while not yet manifesting in tangible construction, proposed a segmentation of buildings into voxels based on specific programmatic requirements. Each voxel was then subjected to optimization algorithms to minimize material consumption. This conceptual framework served as the theoretical cornerstone during the progression of our study.
Site
Cairo, the site chosen for the project, is emblematic of a thriving metropolis struggling with ever-increasing population numbers. The city is witnessing a growth of informal settlements marked by increasing density, predominantly manifested vertically due to spatial constraints. In particular, local vernacular architecture incorporates wood in the form of pigeon towers, an integral part of the community. In this context, the research contemplates a wooden lattice system, characterized by its lightness and modularity. This consideration is essential, given the inherent instability of existing structures used for expansion in this setting in Cairo. Faced with the demands of rapid urban expansion, the research aims to improve the residents’ experience through a programmatic approach that is adaptable to evolving needs.
Material
One of the main challenges is to mitigate the constraints imposed by the scarcity of wood resources in Cairo. Despite the historical absence of indigenous wood in the city, some recent initiatives by government and private entities in southwest Egypt, have looked into harnessing the potential of palm trees and their residues for the production of engineered wood products, such as MDF and robust manufactured wood beams. In addition, considerations extend beyond timber to encompass complementary materials such as steel for connections, glazing, insulation, etc. Our research favors an integrated approach that takes advantage of indigenous palm trees, involves local communities, leverages government financial support and takes advantage of the existing transportation infrastructure network. This multi-faceted strategy aims to align architectural innovation with environmental sustainability, community involvement and economic viability.
Strategy
The undertaking of this project involved an exploration of the anatomy of the lattice system. Our main objective was to acquire an understanding of the system, delineating its inherent advantages, disadvantages, and general characteristics. Initial explorations involved a systematic investigation of the lattice system, its potential, covering both vertical and horizontal configurations. Essential to this was an in-depth examination of module characteristics: size, type, layering, voids, density, and shape. This experimentation included a detailed examination of the spatial options achieved by manipulating points between layers, resulting in a variety of spatial configurations. Quantitative analyses were performed to evaluate key parameters such as the number of structural members and nodes relative to the overall size, which contributed to an informed design framework. This initial investigation paved the way for an in-depth examination of potential applications of the lattice system in the specific urban context of Cairo in later stages.
Our methodology moved from a general analysis to a detailed specific exploration focusing on the architectural qualities of the system. The general process began with an urban-scale analysis, in which computational tools were employed to examine the site from a holistic perspective. This macro analysis allowed for a contextual integration of the lattice system, informed by the unique characteristics of Cairo’s urban environment. Subsequently, the research progressed further into the development of a more specific architectural program, incorporating specialized activities for the buildings. An integral facet of this phase involved the application of optimization processes to identify and refine optimal solutions. This methodological approach was instrumental in ensuring the adaptability and effectiveness of the lattice system within the complex urban dynamics of Cairo. Going deeper into the materiality intricacies and external skin of the architectural project, this phase sought to achieve a smooth integration of aesthetic considerations, structural integrity, and sustainable material choices. The goal was to create a system that not only responded to the inherent characteristics of the lattice, but also resonated with the specific urban challenges and opportunities present in Cairo.
Macro Scale
At the macro-scale, the project aspired to formulate a system capable of responding dynamically to the unique constraints of the community. Central to this aspiration was the development of a program generated based on the estimated population of the area. Recognizing the anticipated expansion of the residential components, the program incorporated essential community facilities such as gymnasiums, day care centers, classrooms, and open spaces. Given the high population density characteristic of the area, the integration of rooftop open space emerged as a strategic opportunity to alleviate urban congestion. Emphasis on community involvement permeated the design philosophy, contemplating initiatives such as rooftop farming and the preservation of the pigeon tower tradition. The programmatic layout on the site was closely tied to the estimated population, ensuring a sensitive and contextualized deployment of each element. This approach underscores the project’s commitment to address macro-, meso- and micro-scales, with due regard for urban functionality, environmental sustainability, and cultural continuity.
The integration of residential and community elements into the lattice system was carefully coordinated, with a focus on optimizing spatial configurations and minimizing logistical complexities. Residential components were strategically placed on all rooftops, consistent with a distributed model. Conversely, the allocation of community facilities depended on the estimated number of residents, coupled with a strategic reduction of walking distances. An environmental analysis was employed to identify suitable locations for rooftop farming, distinguishing areas conducive to summer and winter crops. Open spaces, vital to the well-being of the community, were carefully distributed throughout the urban proposal.
Meso Scale
When transitioning to on-site implementation and after selecting the intervened rooftops, certain parameters were defined to regulate their impact on the existing structures. The selection of roofs for the lattice system was adjusted to predetermined volume constraints, based on the actual volume and height of each existing building. In addition, a minimum floor area was stipulated as a starting point, and subsequent optimization procedures focused on solar exposure in relation to floor area. The aim of this iterative process was to achieve configurations that would integrate seamlessly with existing buildings and roofs while respecting a compact layout. Structural optimization was a critical aspect of the project, which began with an initial configuration of diagonal elements only. Subsequent iterations incorporated a combination of diagonal members and orthogonal frames, with favorable results through the application of optimization algorithms. In particular, the BESO (Bidirectional Evolutionary Structural Optimization) strategy focused on the elimination of underutilized elements, guided by a target mass ratio of 50%. This approach facilitated the use of slender elements with a 10-centimeter cross-section. Further optimization procedures were performed increasing material efficiency, resulting in a reduction of approximately 60% in material quantity and 56% in weight with a target mass ratio of 35%. This optimization process highlighted the commitment to sustainability, resource efficiency and sensible use of materials in the implemented lattice system.
Optimization of the structural configuration also became a critical factor in reducing the environmental impact associated with the structural frame. A comprehensive Life Cycle Assessment (LCA) was conducted to measure performance before and after structural optimization. The initial carbon footprint of 110 kg CO2 per square meter was significantly reduced to 43 kg CO2 per square meter, an impressive reduction of approximately 60%. Consequently, the project’s sustainability rating was upgraded from A to A++. This substantial reduction underscores the effectiveness of structural optimization in bringing the project in line with the highest environmental standards.
Micro Scale
A typical residential unit, designated as the most prevalent within the program, reveals a subtle spatial organization, a bifurcated volume, distinguished between outdoor and enclosed spaces. The exterior volume encompasses various programs, such as courtyards, workshops, and urban farms. The assembly of architectural elements, including floor panels, wall panels and shading devices, come together to form the enclosure with adaptive shading provisions. The project grows out of the site, recognizing material constraints and requiring local solutions. The use of palm tree trunks, otherwise considered waste, emerged as a pragmatic alternative, resulting in reinforced MDF posts and boards for the structural frame and floor panels, respectively. In addition, palm tree trunks were harnessed to create fenestration panels, employing local techniques to achieve a distinctive aesthetic. A sustainable approach was also manifested in the incorporation of recycled cotton canvas, derived from Egypt’s cotton waste, which serves as shading devices. This not only reduces reliance on foreign materials, but also encourages environmentally friendly local businesses, fostering economic growth in rural agricultural areas.
Clustering
The site planning strategy adopted for this project went beyond the constraints of an isolated unit to articulate a comprehensive system capable of anticipating its overall growth on the selected site. This forward-looking approach involved a dynamic mix of locally developed programs. The predictive model involved analyzing the interrelationships between the various programs, their spatial proximities, and the available rooftop area. This in turn manifests in a holistic and integrative approach to urban development.
The transition from an urban context to an immersive experience of the living spaces and their functionality prompted an in-depth exploration of modularity, flexibility, and adaptability within the proposed system. A key consideration in this effort was the anticipation of organic growth and the potential evolution of users’ needs over time in response to factors such as government initiatives and population shifts. A module capable of versatile transformations underscored our commitment to addressing the dynamic nature of urban spaces. The conceptualization of a module adaptable to diverse functionalities was a central element of this exploration. The residential module layouts called for two or three bedrooms, this configuration resonates with family-oriented existing urban context where this type of housing is common. More importantly, the same module seamlessly transforms to accommodate common spaces, subdividing into areas suitable for daycare centers, classrooms, workshops, and similar activities. This multiplicity of functions ensures the system’s relevance to diverse user needs and urban setting.
A notable feature of the system lies in the strategic parameterization of the bracing system. Located on the exterior when it lacks interior connections, the bracing system allows for flexibility within interior spaces. Internally, a common beam system is used, with the bracing strategically placed on the outside of the structure. This design decision facilitates spatial adaptability and configuration adjustments without compromising structural integrity.
The program extended to anticipate system growth on the rooftops of Cairo, where the lattice system plays a key role. This extension of the system complements the habitable units with vegetation, horizontal common areas, and urban agriculture where feasible. Subsequent iterations seamlessly combine conceptual visions with tangible applications. Throughout the process, a series of visualization generated through artificial intelligence were created. This step synthesizes the conceptual with the emotive, transcending mere spatial considerations to evoke a sense of place and atmosphere. The resulting images are a compelling testament to the harmonious integration of the design concepts with the urban reality of Cairo.
