With heightened awareness of issues surrounding climate change, a much-needed movement arguing for meaningful action within the field of architecture has emerged. The weight of the problem we face is huge. For example, the built environment accounts for 40% of the UK’s total carbon footprint. Whilst this statistic is alarming, work is being done to ease the negative impacts of buildings on our planet. Opting to use natural materials in construction is one of many ways in which we can move towards sustainability within the industry. Although there have been many natural material innovations in recent years, these materials must be made more widely known and adopted if we are to reach the ambitious targets we have set ourselves.
1. Adobe Bricks
The adobe block is one of the most traditional naturally sourced materials used in construction. It is essentially a brick composed of earth, water, and additional organic material such as straw. Architects in some areas of Latin America make the bricks waterproof using fermented cactus juice. In construction, networks of these bricks are often held together by a mud mortar or any other mortar that is weaker than the bricks themselves. As long as they are well maintained, adobe-based structures can be highly resilient. In fact, San Miguel Chapel, one of the longest surviving structures in the United States is made from adobe blocks.
Limecrete is a very breathable material composed of natural hydraulic lime and sharp sand, occasionally being mixed with glass fibers for enhanced durability. Floors made from limecrete offer great levels of thermal efficiency when paired with a suitable insulator such as recycled foam glass, and the material has more than enough strength to be used in construction. It is highly proficient at handling the natural moisture levels of a site and is therefore frequently adopted in old buildings to prevent damp penetration.
Composed of hemp, hurds, and lime, hempcrete is a newly emerging natural material that allows for the creation of buildings with significantly lower carbon footprints. Hemp blocks regulate the humidity within spaces and provide many benefits in the form of fire resistance and acoustic insulation. It can also extract carbon from the air and store heat. Its ability to absorb moisture means that hemp-based building materials are resistant to mold and can also store water which can be released into the ground or recycled.
4. Mycelium Bricks
Mycelium, the group of threads from which mushrooms develop, can be used as an insulator or as a replacement for bricks. Natural materials such as mycelium release significantly less carbon dioxide into the atmosphere than traditional building materials such as concrete. Another great property of mycelium bricks is that they are biodegradable, leaving behind less harmful waste. A number of different mycelium-based structures have been successfully built over the past few years, including The Growing Pavillion, a temporary installation designed by Pascal Leboucq in collaboration with Krown Design for Dutch Design Week.
When harvested responsibly through sustainable forestry, which involves planting more trees than are cut down, timber can be an incredibly sustainable building material. In fact, timber has the lowest embodied energy of any conventional building material. Not only is it almost infinitely renewable, but it also yields many benefits when adopted in architecture, such as reduced on-site construction time and the relative lightness of large components. Timber is also a remarkably versatile material since different tree varieties have unique visual and physical properties.
6. Rammed Earth
By working aggregates such as sand, gravel, clay, and silt into the form of walls, buildings can be constructed which not only are sturdy and sustainable but also possess a traditional aesthetic that encourages a harmonious connection with nature. Rammed-earth construction is better suited to warm and dry climates and is therefore popular in Australia. Measures can be taken to protect such structures from potentially damaging weather conditions, for instance, the building can be raised above the ground and roof overhangs can be put in place to shelter the walls from rain.
Subsoil can be mixed with water, straw, and in some cases lime to produce cob, a building material that is said to date back to prehistoric times. The material has grown back in popularity over recent years in parallel to the emergence of a grand movement towards a more sustainable built environment. An advantage of cob construction is that walls can take on practically any shape since they are crafted manually into forms. Although this construction process is long-winded, cob is a cheap material that is fire-resistant, can withstand seismic activity and provides great thermal insulation.