Learning from the desert snail

“Life´s been on earth for 3.8 billion years, and in that time life has learned what works, and what´s appropriate here and what lasts here. The idea behind biomimicry is that perhaps we should be looking at these mentors, at these biological elders. They have figured out how to create a sustainable world. So rather than inventing it from scratch, why don’t we take our cues from them. These are Earth savvy adaptations”1   

Janine Benyus  

 

Most people associate deserts with lifelessness, desolated places with unbearable high temperatures and lack of water, places that not only human beings but also most other species are not designed to live in. Meanwhile, through the millions of years of evolution nature has managed to develop special adaptations in some animals that make them suitable for such kind of arid environments. One of them is the desert snail.

This short research focuses on the desert snail’s (Sphincterochila Boisseri) adaptations to the hot desert conditions, and how the small creature’s surviving strategies can be implemented into architecture in hot and arid environments.  

The organism has been chosen based on both the climatic and cultural similarities that its habitat has to the country where our site is located in, Morocco.   

 

 

1. Adaptations of the snail

1.1 Withdrawal inside the Shell

The habitat in  which the desert snail lives is characterized as being barren. The lack of vegetation reduces the possibilities of hiding from or reflecting solar radiation before it reaches the animal. Consequently, gaining heat by direct solar radiation is one of the main threats to the life of the desert snail. Therefore the snail’s ability to retreat inside the shell and avoiding direct exposure to the sun is considered as the most important survival mechanism.

 

1.2 Reflective shell

Its highly reflective white shell compensates for the lack of hiding opportunities and reflecting surfaces in the snail’s environment. The shell has the ability to reflect 90% of visible solar radiation, and 95% of infrared radiation. As a result of this high reflectivity, the radiation heat flow does not reach the snail2 (Fig. 1)

1.3 The shape of the shell 

  • Curved surfaces in hot dry climate maintain lower temperatures and reflect more radiation than flat surfaces. The intensity of solar radiation is spread over a larger area, meaning that the average heat increase of the surface and heat transmission to the interior are reduced3 (Fig. 1)
  • Due to the shell’s curvature, it touches the ground in only few spots reducing direct contact with the overheated ground. In the same time it allows air to flow in and be captured between the soil surface and the withdrawn snail, creating an insulating air cushion. The air cushions heat blocking results in a lower temperature in the highest part of the shell allowing the snail to maintain its body temperature and not overheat.2 (Fig 1)

 

1.4 Shade 

The temperature of the soil surface under the snail is lower comparing to the surrounding environment. The specific spot is shaded by the snail’s shell, which extends beyond the actual size of the snail as it is lifted from the ground due its shape2 (Fig. 1)

1.5 Heat flow and air movement

As a result of temperature differences between the components surrounding the snail, heat flows by conduction from higher temperatures in the ground and the lower part of the shell to the surrounding air, and not through the highest part of the shell where the snail dwells2 4 (Fig. 1-2)

 

 

 

 

graf-over-temperatur

Fig. 2 – Temperature differences between the components surrounding tha snail.

 

1.6 Evaporative cooling

The snail absorbs and stores water at night by sucking up moisture from the soil, and then releases the water through evaporation during the day when temperature increases. 4    (fig 3)

 

vekttap

Fig. 3 – Weight gain at night and a loss during the day due the evaporativ cooling.

Many of the techniques mentioned above have already been used in vernacular architecture:

                        iranian-mud-house       hvitt palas.jpg

            evaporative-cooling            mashra

Based on the findings that have been observed both in the snail´s and in ancient vernacular architectures cooling methods can we apply the same principles, but with different interpretation forming a new architectural expression that usually doesn’t exist in Saharan areas.     

2. Adaptations applied to architecture

2.1 Curved roofs

With help of 3D programs and different modelling techniques, curved roofs and structures can be calculated and formed beyond the vault and dome limitations. The structures can be customized for several needs such as shading, ventilation, elevation from the ground and creating different levels. Complex curved shapes will also give the architecture a different expression.

shell-roof-1

Complex curved structure made of bricks by Block research group

shell-roof-4

Complex curved structure made of steel and nylon by MATSYS 

2.2 Surface

Methods such as reflective white coatings or white tiles could be used in order to mimic the highly reflective white surface of the desert snail. The use of tiles will also give the possibility to control penetration of light into a structure, but also refer to Islamic architecture and its historic use of tiles.

      white coating.jpg               white-mosaic-tiles

2.3 Evaporative cooling 

ECOoler is a tile system that connects via water hose nozzles, creating a grid of cooling elements that work by evaporating water. The form of the tiles is inspired by the mashrabiya, a traditional Arabic shading wall. In the ECOoler, the Mashrabiya is molded and made into a tube system that contains cooling water. The tiles are made out of clay, which allows the water to evaporate and seep through the clay when in contact with warm air. The traditional Jara jug inspires the use of a clay container filled with cooling water. The use of a clay container filled with cooling water is inspired by the traditional Jara jug.5 (Fig. 4-5)

 

 

 

References:

(1) Janine Benyus –  http://www.huffingtonpost.com/leila-conners/biomimicry-solution-problems_b_8401268.html

(2) Adaptations of the snail –  http://www.asknature.org/strategy/1683ae77eb0b8030d6c81e7098ddcd3c

(3) The shape of the shell –  https://www.researchgate.net/publication/223063885_Thermal_behavior_of_curved_roof_buildings_exposed_to_solar_radiation_and_wind_flow_for_various_orientations

(4) Heat flow and air movement –   http://jeb.biologists.org/content/jexbio/55/2/385.full.pdf

(5) ECOoler – http://www.yankodesign.com/2011/02/09/analog-cooling-of-interior-spaces/

 

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