The number of people living in earthen homes around the world, researchers believe, has dropped sharply from one in three to one in 10 to 12. Despite this, an estimated 650 to 750 million people currently inhabit buildings made from natural materials such as rammed earth, adobe blocks, wattle and daub (interwoven sticks and twigs covered with mud or clay), and compressed earth blocks.

The concern among scientists is that this group represents a potential “emissions time-bomb,” should those inhabiting earthen structures, which have a light environmental footprint, move to brick or concrete dwellings, which generate far more carbon emissions as a result of producing the materials to construct them.

A study by scientists at the University of Leeds and Delft University of Technology in the Netherlands makes this case. The researchers examined census data and national statistics from the 26 countries that are home to three-quarters of the world’s population.

As nations become richer, the study found, a smaller proportion of the population live in earthen buildings. This is believed to be the result of population growth, in part, a shift from rural communities to urban areas and attitudes that favor homes made from modern materials as more desirable.

Dr. Alastair Marsh, research fellow in the School of Civil Engineering at Leeds and lead author of the paper, said: "The big issue is, how can we ensure the whole world's population is living in safe, affordable housing in line with UN Sustainable Development Goals as soon as possible and at the same time avoid producing excessive carbon emissions from building houses that will lead to further climate change?”

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Marsh stated that the issue is one of balance — using less material overall and using materials that are appropriate for the region.

"Earth materials have excellent environmental performance but have rapidly been falling out of favor in many parts of the world in recent decades. To challenge those negative attitudes, we need to focus on making earthen homes that are healthy, stylish and that people can really want to live in," he added.

Yask Kulshreshtha, Ph.D. researcher in the Faculty of Civil Engineering and Geosciences at Delft University of Technology and co-author in the paper, explained that the local soil used to build earthen homes can be re-used multiple times, and that these structures are energy efficient because they control indoor temperature and humidity. "With several ecological advantages, earthen homes are a good bet for reducing greenhouse gas emissions."

Low-cost design measures can be taken to prevent insects and other disease-transmitting organisms from entering earthen homes through open eaves. The study authors found that in some wealthier countries, modern versions of these homes are gaining greater acceptance.

The study is published in Building Research & Information (2021)

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