Tafonic - a Desert Habitat

Coober Pedy, known for its opal mines, is also famous for its harsh desert climate with temperatures often exceeding 45°C. The town’s residents have adapted by creating underground homes that utilize natural insulation to stay cool.

As a senior with architecture university aspirations, I am always excited to learn more about architecture and how it can help our society and environment. In this project, I explore passive cooling techniques that blend with Coober Pedy’s environment. By combining traditional wind catchers with the porous structures of tafoni sandstone, my design aims to provide a sustainable, comfortable habitat. This design not only addresses the challenges of Coober Pedy’s harsh climate but also offers a sustainable and unique solution that can hopefully inspire change.

• Revit (used for interior modeling and ideation)
• Rhino 8 (for computer-generated design with Voronoi)
• Affinity Design (for image editing and vector drawing)
• Fusion (for generative design and stress-testing)
• Twinmotion (for model rendering)

To run this software, it is preferable to have a computer with a powerful graphics card for faster rendering. Personally, I used an Asus Tuf laptop. Fortunately, most software offers free (i.e. Revit, Twinmotion) or discounted (i.e. Rhino, Affinity Designer) licenses for students, however, some will require a Windows operating system.

Created and popularized for its significant opal reserves for mining, Coober Pedy has been frequently called the “Opal capital of Australia”. However, Coober Pedy’s climate is extremely harsh, in a desert of sandstone and sand. With extreme heat, barren vegetation, and dry air conditions, temperatures can often exceed 45°C. Despite annual average highs of 28 °C, the town’s ~2,000 residents adapted to escape the heat. Many residents dug underground homes to utilize the Earth’s insulation to keep homes cool, resulting in Australia's famous underground city. 

This ingenious design demonstrates how architecture can leverage natural conditions to ensure inhabitants’ well-being. However, designing a habitat for these conditions will need to solve these challenges.

• Extreme temperatures: Advanced thermal control will be necessary to manage temperatures exceeding 45°C.
• Air quality: The design must include measures to manage dry air and ensure good air quality within the habitat.
• Isolation: The psychological impact of living in a remote and extreme environment will be addressed through design to promote mental well-being and social interaction.

According to a 2018 report by the International Energy Agency, “using air conditioners and electric fans to stay cool accounts for nearly 20% of the total electricity used in buildings around the world.” This heavy reliance on air conditioners not only significantly contributes to energy consumption but also exacerbates global warming and thus air conditioner usage. As a result, we are now seeing a critical need to explore alternate cooling techniques in modern design.

My project focuses on creating a habitat that harmonizes with Coober Pedy’s environment, promoting energy conservation and following LEED criteria. The designs should be iconic, functional, and inviting, encouraging interaction and engagement with the extreme environment. 

Wind catching towers, also known as wind towers or wind scoops, are traditional architectural elements primarily found in hot and arid regions like the Middle East. These towers capture prevailing winds and direct them into buildings to provide natural ventilation and cooling. 

Typically constructed with openings at the top and sometimes at various levels, wind catching towers work on the principle of cross-ventilation: as wind passes through the tower, it creates a suction effect that draws hot air out of the building while cooler air is drawn in.

This ancient cooling technique dates back centuries and remains an important feature in Middle Eastern architecture, showcasing a sustainable approach to environmental design that reduces reliance on energy-intensive air conditioning systems. Today, wind catching towers continue to play a vital role in moderating indoor climates, preserving cultural heritage, and promoting sustainable building practices in the region.

When I first looked to Coober Pedy’s surrounding environment of barren sandstone for inspiration, I came across a unique process of sandstone weathering called “tafoni.” Tafoni occurs when intense weather conditions like sun, sea, and wind gradually erode sandstone, forming intricate, porous structures that enhance air movement through their cavities. These formations can be found in nearby regions such as the Gawler Ranges.

The porous nature of tafoni sandstone, characterized by its weathered cavities and smooth, curved surfaces, sparked the idea to incorporate these organic shapes into my design. My exploration into porous structures led me to research papers confirming that high porosity structures can significantly improve thermal conductivity. Inspired by these findings, I decided to integrate the porous features observed in tafoni sandstone into my architectural design, aiming to optimize natural ventilation and effectively dissipate heat from the habitat.

By combining the naturally venting natural rock formations with the ingenious cooling systems of wind catch towers, I envisioned a dwelling that seamlessly blends with the desert landscape while providing a comfortable, sustainable living environment. The building will withstand hot temperatures due to the passive cooling system that utilizes a constant inflow of cool air from air vents on the side, combined with hot air rising and escaping through the pores.

The design harmonizes with its surroundings, paying homage to the natural artistry of tafoni sandstone and the cultural heritage of Middle Eastern architecture. This fusion results in a home that is both a functional refuge from the desert heat and a tribute to the timeless beauty of natural and traditional structures.

To create a porous design that emulates tafoni patterns, I started with Voronoi patterns. A Voronoi pattern divides a plane into randomly generated regions, each linked to a population of points, creating randomized patterns. To make this, I used Grasshopper, an algorithmic modeling tool integrated with Rhinoceros 3D. Through nodes carrying unique functions, you can create complex parametric designs, like with the Voronoi node.

Next, I extended the Voronoi pattern into a three-dimensional space by generating Voronoi cells within a cube. This was accomplished by using the Populate 3D and Voronoi 3D components in Grasshopper, transforming the flat Voronoi cells into a volumetric partitioning, setting the foundation for our 3D structure.

To create a cohesive form, I deconstructed the 3D Voronoi cells and selected random chunks to merge into a single shape. By sorting and combining these randomly connected cells into lists, I crafted a unified structure, moving from individual cells to a comprehensive 3D model.

I refined the combined shape by bevelling the corners to smooth out edges and improve the visual appeal. Additionally, I created distinct surfaces for windows, walls, and other architectural elements, using Grasshopper to precisely define and position each component, enhancing both functionality and aesthetics.

Consolidating the nodes into a single flowchart will result in a randomized computer-generated shape. Using Grasshopper's "bake" function to convert it to a solid, I then exported it into Revit to add details and model the interior.

While the surface structures must ventilate hot air, Coober Pedy is prone to sudden warm winds that can carry dust storms. If windows can not close, hot breezes could enter and warm the habitat.

To control the windows with the least amount of energy, I designed a system that props windows open using push knobs, which are remotely triggered. This mechanism allows for controlled opening and closing of the windows to optimize airflow and temperature regulation within the building.

The design includes a safety feature that responds to Coober Pedy’s characteristic warm winds, such as those during a dust storm. When a strong warm wind attempts to enter, the windows, being set at a slight angle, will be pushed closed by the wind’s force. This prevents hot air and dust from entering the building, maintaining a cooler and cleaner indoor environment.

Research supports the effectiveness of angled windows and magnetic push knobs in regulating airflow and temperature. According to a study published in the Journal of Wind Engineering and Industrial Aerodynamics, angled windows can significantly reduce the entry of dust and hot air while allowing for sufficient ventilation under normal conditions.

To supply cool air into the habitat, multiple air intake systems will be introduced at ground level. This system draws cool air from the surface and channels it into the living spaces below. The intake vents are strategically positioned and designed to capture cooler air, which naturally sinks into the underground structure due to gravity and the temperature difference. As the cool air flows through the underground pathways, it absorbs heat from the surroundings, thereby reducing the indoor temperature. This passive cooling method is highly effective in maintaining a comfortable and sustainable living environment, leveraging the natural insulation properties of the Earth and reducing reliance on energy-intensive cooling systems.

My habitat below ground adopts many of the same motifs from the surface dome, such as a cylindrical form connected via a spiral staircase. Additionally, the spiral staircase not only connects the levels but also acts as a conduit for rising warm air. To ensure effective heat dissipation and a sense of connection to the surface, the floors are designed with gaps that allow heat to rise naturally. This interconnected space promotes efficient ventilation and maintains a comfortable living environment. By opening up the floors, heat can naturally ascend and exit through the upper openings, promoting a cooler and more comfortable living space below.

I used Revit to model out the interior, beginning with a floorplan

The living area is a spacious, open concept that serves as the central hub of the habitat. The circular layout, combined with the spiral staircase, creates a fluid transition between the levels. Comfortable seating surrounds a central point, fostering a communal atmosphere ideal for social interaction. The open design also aids in heat dissipation, allowing warm air to rise through the gaps between the levels.

The kitchen and dining area are designed for both functionality and aesthetics. The kitchen features modern appliances and ample counter space, encouraging efficient meal preparation. Adjacent to the kitchen, the dining area is bathed in natural light from strategically placed openings in the ceiling. This design not only enhances the dining experience but also aids in ventilation, ensuring that cooking heat rises and exits the living space.

The bathroom is a blend of luxury and practicality, featuring high-quality fixtures and a sleek, modern design. Marble surfaces and wooden accents create a soothing environment. The bathroom's location and design ensure privacy while also incorporating ventilation features that allow moisture and heat to dissipate effectively, maintaining a comfortable and dry atmosphere.

The bedroom offers a cozy retreat with a focus on comfort and relaxation. The design includes soft, inviting textures and a minimalist aesthetic. Openings near the ceiling ensure that warm air can escape, maintaining a cool and pleasant sleeping environment. The connection to the rest of the habitat through open spaces ensures that the bedroom remains well-ventilated.

The materials chosen for this project are selected for their sustainability, durability, and ability to harmonize with the natural environment of Coober Pedy. The primary material is locally sourced sandstone, which not only blends aesthetically with the surrounding landscape but also offers excellent thermal mass properties, helping to regulate indoor temperatures. 

The windows are tinted to reduce solar heat gain, minimizing the amount of heat from sunlight entering the building and helping to maintain a cooler indoor environment. This feature is crucial in a desert climate where temperatures often exceed 45°C. The high-performance glazing of the windows also enhances thermal insulation, further contributing to energy efficiency.

Given the structure's design, which incorporates many panels with windows, prefabricated wall panels are an optimal choice. Research indicates that Structural Insulated Panels (SIPs) offer excellent thermal performance, durability, and ease of installation. SIPs consist of an insulating foam core sandwiched between two structural facings, typically oriented strand board (OSB).Additionally, prefabrication ensures consistent quality, reduces construction time, and minimizes waste, aligning with the project's sustainability goals.

The interior design of this underground habitat balances functionality, comfort, and environmental considerations. Each section—living area, kitchen, dining area, bathroom, and bedroom—is thoughtfully designed to ensure efficient heat management and ventilation. This interconnected space provides a sustainable and comfortable living environment, perfectly suited to the extreme conditions of Coober Pedy.