Termites and buildings are rarely seen as compatible. But researchers say that learning more about termites’ architectural strategies could help engineers design more energy-efficient, self-sustaining buildings.

Many species of termites, whose societies are built on hierarchies of kings, queens, workers and soldiers, live in towering nests that are ventilated by a complex system of tunnels.

Termite mound. Source: Jim Bendon / CC BY-SA 2.0The nests, known as mounds, can grow as tall as 7 m. They are also self-cooling, self-ventilating and self-draining.

A group of engineers, biologists, chemists and mathematicians led by Imperial College London, the University of Nottingham and CNRS-Toulouse have used 3D X-ray imaging to look closer at how these nests work. The researchers found small holes, or pores, in the walls of termite mounds which help them stay cool, ventilated and dry.

In their study, published in Science Advances, the researchers sourced termite nests from the African countries Senegal and Guinea and studied them using two types of 3D X-ray imaging.

First, they scanned the nests at a lower resolution to measure the nests’ larger features, like walls and corridors known as channels.

From the images they calculated the thickness of the nests’ inner and outer walls, as well as the structural details of inner channels, which termites use to get around the nest.

The researchers found that networks of larger and smaller pores in the nest walls help exchange carbon dioxide (CO₂) with the outside atmosphere to help ventilation. Larger micro-scale pores were found to be connected throughout the outer wall providing a path across the walls, and by using 3D flow simulations, the authors showed how CO₂ moves through the nests to the outside.

The simulations showed that the large micro-scale pores in nest walls are useful for ventilation when the wind outside is faster, as CO₂ can leave freely. However, in slower wind speeds, the larger pores can also help to release CO₂ through diffusion.

Keeping critters cool

Nests are usually found in hotter regions, which means they must stay cool. The authors found that the larger pores also help regulate temperatures inside nests. The pores, which lie in the outer walls of the nest, fill with air which reduces heat entering through the walls. The researchers said this is similar to how the air in double-glazed windows helps keep the heat inside.

Considering the crucial role the pores play, the team also wondered what happens when it rains and the pores become blocked by water.

They found that the nests use capillary action where liquid flows through small spaces without external help from gravity to force rainwater from the larger pores to the smaller pores. This design ensures the larger pores keep stay open to keep ventilating the nest.

The scientists say the newly found architecture within termite nests could help human designers improve ventilation, temperature control and drainage systems in buildings.

The research was funded by the Engineering and Physical Sciences Research Council, the Royal Society and the Wolfson Foundation.