How termite mounds can teach us to create comfortable interior climates

Termites, with their remarkable ability to construct complex mounds, offer valuable lessons to human architects and engineers. These tiny insects have honed their mound-building skills over millions of years, resulting in structures that can reach heights of up to eight meters, making them some of the largest biological formations in the world. By studying the design principles behind these mounds, we can gain insights into creating sustainable and comfortable interior climates for our buildings without relying heavily on energy-intensive air conditioning.

In a recent study published in Frontiers in Materials, researchers explored how termite mounds can serve as inspiration for innovative architectural approaches. The study, led by Dr. David Andréen from Lund University’s bioDigital Matter research group, focused on the intricate network of interconnected tunnels known as the “egress complex” found within termite mounds. This network plays a crucial role in facilitating the flow of air, heat, and moisture within the mound.

By understanding and emulating the principles of the egress complex, human architects and engineers can develop new strategies to enhance the natural ventilation and climate control of buildings. The termite-inspired designs can promote efficient airflow, temperature regulation, and humidity management, all while reducing the reliance on traditional air conditioning systems and their associated carbon footprint.

By adopting the lessons learned from termite mounds, human architecture can embrace biomimicry—a practice that draws inspiration from nature to solve engineering and design challenges. This approach not only holds the potential to create more sustainable and environmentally friendly buildings but also introduces innovative and efficient ways to maintain comfortable indoor environments.

As scientists delve deeper into the intricacies of termite mound architecture and its impact on interior climates, we can look forward to a future where human-built structures harmonize with nature, taking advantage of the wisdom that termites have perfected over millions of years.

Termites from Namibia

Drs. David Andréen and Rupert Soar conducted a study on Macrotermes michaelseni termites in Namibia, focusing on their mounds and the intricate egress complex within them. These mounds can house colonies of over a million termites and contain symbiotic fungus gardens that serve as their food source.

The researchers specifically examined the egress complex, which is a densely woven network of tunnels measuring between 3mm and 5mm in width. These tunnels connect larger conduits inside the mound with the external environment. During the rainy season, spanning from November to April, the egress complex extends over the north-facing surface of the mound, directly exposed to the midday sun. However, outside of this season, termite workers seal off the egress tunnels. The purpose of this complex is believed to be twofold: facilitating the evaporation of excess moisture and ensuring adequate ventilation within the mound. But how does it achieve these functions?

By studying the egress complex and its mechanisms, researchers aim to uncover the secrets behind its efficient regulation of moisture and airflow. Understanding these processes could inspire innovative solutions for human architecture, enabling the creation of comfortable and well-ventilated spaces without relying heavily on energy-consuming technologies like air conditioning.

The study conducted by Drs. Andréen and Soar sheds light on the fascinating strategies employed by termites to maintain optimal environmental conditions within their mounds. By unraveling the workings of the egress complex, researchers are paving the way for potential applications in human-built structures, fostering sustainable and energy-efficient designs inspired by nature’s own architects.

Termite mound in Bangalore, India. Credit: D. Andréen

Dr. David Andréen and Dr. Rupert Soar conducted experiments to investigate the layout of the egress complex and its ability to facilitate oscillating or pulse-like flows. To conduct their research, they utilized a scanned and 3D-printed replica of an egress complex fragment obtained from the wild in February 2005. This replica was 4cm thick and had a volume of 1.4 liters, with approximately 16% of its composition consisting of tunnels.

In their experiments, the researchers simulated wind effects by using a speaker to generate oscillations of a CO2-air mixture through the replicated fragment. They closely monitored the mass transfer using a sensor. Through their investigations, they made interesting discoveries about the behavior of air flow within the egress complex at different frequencies.

The results of their experiments indicated that the airflow was most significant when oscillation frequencies ranged between 30Hz and 40Hz. At these frequencies, the movement of air through the tunnels was the most pronounced. Airflow was moderate at frequencies between 10Hz and 20Hz, while frequencies ranging from 50Hz to 120Hz demonstrated the least amount of airflow.

By understanding the relationship between oscillation frequencies and air flow within the egress complex, researchers like Drs. Andréen and Soar aim to extract valuable insights for creating more efficient ventilation systems in human architecture. These findings provide a starting point for developing innovative design strategies that can harness natural ventilation principles observed in termite mounds, ultimately leading to environmentally friendly and energy-efficient building practices.

Turbulence helps ventilation

Based on their experiments, Dr. David Andréen and Dr. Rupert Soar reached a conclusion regarding the interaction between the tunnels in the egress complex and the wind blowing on the termite mound. They discovered that these tunnels have a significant impact on enhancing the mass transfer of air, which in turn promotes effective ventilation.

The researchers observed that when the wind interacts with the egress complex at specific frequencies, it generates turbulence within the mound. This turbulence plays a crucial role in facilitating the movement of respiratory gases and excess moisture away from the core of the termite mound. By harnessing wind oscillations at these optimal frequencies, the ventilation within the mound becomes more efficient.

This finding highlights the sophisticated adaptation of the egress complex to utilize natural wind patterns for enhanced ventilation. By understanding and replicating these principles in human architecture, designers and engineers can develop strategies to improve airflow and regulate moisture in buildings, reducing the need for energy-intensive ventilation systems and promoting more sustainable and comfortable interior environments.

3D scan of fragment of the egress complex of Macrotermes michaelseni termites. Credit: D. Andréen and R. Soar

Dr. Rupert Soar explained that achieving effective ventilation in buildings requires maintaining a delicate balance of temperature and humidity while allowing the movement of stale air out and fresh air in. Traditional HVAC systems often struggle to achieve this balance. However, the structured interface provided by the egress complex offers a solution. It enables the exchange of respiratory gases based on differences in concentration between the interior and exterior, thus helping to maintain optimal conditions inside the structure.

To further investigate the egress complex, the researchers conducted simulations using a series of 2D models that progressively increased in complexity, ranging from straight tunnels to lattice-like structures. They employed an electromotor to drive an oscillating body of water, visibly marked with dye, through the tunnels. The researchers recorded the mass flow using filming techniques.

Surprisingly, the researchers discovered that the electromotor only needed to move the air back and forth over a small distance of a few millimeters, corresponding to weak wind oscillations. This was sufficient to allow the ebb and flow of air to penetrate the entire complex. Importantly, they observed that the necessary turbulence within the system only occurred when the layout of the tunnels resembled a lattice structure.

These findings highlight the importance of the lattice-like arrangement within the egress complex for achieving efficient ventilation. The oscillating movement of air, even over short distances, enabled the desired mass transfer and airflow throughout the complex. By understanding these principles, architects and engineers can develop innovative design strategies that replicate and optimize the lattice-like arrangement, leading to improved ventilation systems that maintain comfortable and healthy indoor environments in buildings.

3D scan of fragment of the egress complex of Macrotermes michaelseni termites. Credit: D. Andréen and R. Soar

Living and breathing buildings

The researchers, Dr. David Andréen and Dr. Rupert Soar, emphasize the potential of the egress complex in enabling wind-powered ventilation in termite mounds even under weak wind conditions. They envision a future where similar networks inspired by the egress complex could be integrated into building walls using emerging technologies such as powder bed printers. These networks would allow for the movement of air within buildings, facilitated by embedded sensors and actuators that require minimal energy.

Dr. Andréen expresses his belief that future building walls could incorporate egress complex-like structures, enabling the efficient circulation of air. These advancements could be made possible through technologies like 3D printing, particularly at the scale of construction. The egress complex serves as an example of a complex structure that has the potential to address multiple challenges simultaneously, including maintaining comfortable indoor environments, regulating the flow of respiratory gases, and managing moisture through the building envelope.

Dr. Soar adds that the development of construction-scale 3D printing hinges on the ability to design structures as intricate and sophisticated as those found in nature, such as the egress complex. By integrating such complex and efficient structures into building design, it becomes possible to create living, breathing buildings that harmonize with nature and provide optimal comfort and functionality.

The researchers’ vision hints at the possibility of a paradigm shift towards nature-inspired construction, where buildings mimic the resilience and efficiency of natural ecosystems. By drawing inspiration from the egress complex and other natural systems, architects and engineers can unlock new possibilities for sustainable, energy-efficient, and environmentally friendly building design.

Source: Frontiers

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