Termite mounds’ “egress complex” helps improve building interior climates.
Some of the 2,000 termite species help maintain ecosystems. The termite genera Amitermes, Macrotermes, Nasutitermes, and Odontotermes build massive eight-meter-high mounds. Natural selection refined these structures over tens of millions of years. How might these hardworking insects help architects and engineers?
A revolutionary Frontiers in Materials study shows how termite mounds might help us design pleasant building interiors. These methods may reduce air conditioning’s carbon footprint, which is encouraging.
“Here we show that the ‘egress complex’, an intricate network of interconnected tunnels found in termite mounds, can be used to promote flows of air, heat, and moisture in novel ways in human architecture,” said Dr. David Andréen, a senior lecturer at Lund University’s bioDigital Matter research group and the study’s first author.
Andréen and Nottingham Trent University assistant professor Dr. Rupert Soar examined Namibian termite mounds. This species may form million-person colonies. Termites grow symbiotic fungal gardens in the mounds for food.
The researchers focused on the egress complex, a dense, lattice-like network of 3mm–5mm tunnels that link bigger conduits within with the exterior. The mound grows throughout the wet season, directly exposed to the noon light. Termites block egress tunnels outside this season. The arrangement is supposed to facilitate moisture evaporation and ventilation. Then how?
Andréen and Soar studied how the egress complicated arrangement allows pulse-like flows. They used a wild egress complex piece scanned and 3D-printed in February 2005 for their research. 16% of this 4cm-thick, 1.4-liter chunk comprised tunnels.
A speaker recreated wind by oscillating a CO2-air mixture through the fragment. A sensor tracked mass transfer. Airflow was highest between 30Hz and 40Hz, moderate between 10Hz and 20Hz, and lowest between 50Hz and 120Hz.
Turbulence aids ventilation.
Researchers found that tunnels in the complex interact with wind blowing on the mound to increase air mass transfer for ventilation. Turbulence from wind oscillations at particular frequencies removes breathing gases and extra moisture from the mound’s heart.
“When ventilating a building, you want to maintain the delicate balance of temperature and humidity without blocking stale air out and fresh air in. Most HVAC systems have trouble. This structured interface exchanges breathing gasses based on concentration differences. Soar explained.
The scientists then recreated the egress complex using 2D models that progressed from straight tubes to a lattice. An electromotor drove an oscillating body of water (dyed) through the tunnels and filmed mass flow. The engine just needed to move air a few millimeters to permeate the entire structure, surprising them. Importantly, only lattice-like layouts generated the requisite turbulence.
At mild breezes, the egress complex can ventilate termite mounds.
We envision powder bed printer-made building walls with egress complex-like networks. “Embedded sensors and actuators that use little energy will move air,” Andréen stated.
Soar concluded: “Construction-scale 3D printing will only be possible when we can design structures as complex as in nature. The egress complex is a sophisticated system that can keep us comfortable while managing breathing gasses and moisture in the building exterior.
For the first time, it may be feasible to create a living, breathing building.
Engineering and Physical Sciences Research Council, Swedish Research Council, and Human Frontier Science Program supported the study.