Nature's ACs: Termite mound-based architectural solutions

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Termite mounds are fascinating structures that serve as a shelter and protective space for termite colonies. But what's really interesting is that they also offer climate regulation.

Termine mounds have sophisticated ventilation systems containing a network of tunnels, channels, and air chambers that allow circulation throughout the structure. This helps to maintain and regulate temperature and humidity.

Architects and researchers have drawn inspiration from termite mounds to develop energy-efficient and sustainable buildings. The most famous example is the Eastgate Building in Zimbabwe, which uses natural ventilation and minimal heating systems to consume lower energy.

Now, new research published in Frontiers in Materials proposes a structure for buildings based on termite mounds that facilitates climate regulation in the interior of buildings. These buildings aim to achieve the effect of air-conditioning but without its carbon footprint.

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The researchers focused on the egress complex—an intricate lattice-like network of tunnels within termite mounds. The researchers conducted various simulations and experiments to study the egress complex and its role in climate regulation.

Breathing buildings: How termite mounds are inspiring sustainable architecture — The egress complex of the Macrotermes michaelseni termite mound.
D. Andréen

They collected samples of the egress complex from a termite mound of Macrotermes michaelseni in Namibia. The unique thing about these mounds is a symbiotic fungus garden that lies in the heart of the structure, farmed by termites for food.

They performed CT scans to analyze the mesh structure, revealing a network of nodes with multiple edges, forming smooth curved channels with a cross-section.

To study the airflow throughout the egress complex, the researchers performed experiments with a three-dimensional replica of its fragment. Then they simulated wind using a speaker to drive an oscillating mixture of carbon dioxide and oxygen through the network.

Upon tracking the movement and exchange of the gases throughout the network, they found that the maximum airflow occurred at specific oscillating frequencies between 30 and 40 Hertz.

In a second experiment, the researchers used transparent acrylic plastic to create 2D models with carious geometries resembling the egress complex. To track the airflow in the egress, they used an electric motor to push oscillating water spiked with a fluorescent dye through the tunnels.

They found that even a slight movement spreads throughout the entire structure. Additionally, they noticed that turbulence, a critical factor, only developed when the layout of the structure was sufficiently lattice-like.

What does this mean for developing living and breathing buildings?

By incorporating interconnected networks which have a lattice-like arrangement, architects and engineers can design buildings that efficiently distribute airflow throughout the structure and reduce dependency on traditional air conditioning, heating, and ventilation systems.

Such living and breathing buildings can lead to improved occupant comfort, health, and well-being by providing a constant supply of fresh air and maintaining optimal indoor climate conditions.

The insights gained from this study offer exciting possibilities for the design of sustainable buildings that promote harmony between architecture and the natural environment.

Study abstract:

In this article we investigate the performative potential of reticulated tunnel networks to act as drivers for selective airflows in building envelopes and thereby facilitate semi-passive climate regulation. We explore whether such transient flow can be used to create functionally graded metamaterials in bio-inspired, additively fabricated buildings. The tunnel networks are modelled on the egress complex found in the mound of certain macrotermite species. The hypothesis we explore is that oscillating airflow of low amplitude can be used to generate large scale turbulence within the network and thereby increase the mass transfer rates across the network. The hypothesis is tested through a series of 3-dimensional and 2-dimensional experiments where various geometries are exposed to a forced oscillation of the air or water column. The results are evaluated in the 3-dimesional experiments through tracer gas measurements, and in the 2-dimenstional experiments through visual qualitative assessment using fluorescein dye. We find that the oscillating fluid gives rise to large scale turbulence that causes a net mass transport across the tunnel network, and that this turbulence occurs when certain combinations of amplitude, frequency, and network geometry are achieved. Furthermore, we conclude that the net mass transfer is large enough to be functionally useful in a building envelope as a method to regulate either building interior climate or the envelope’s own microclimate.