Owing to climate change and economic crises, the architecture of the 21st century must be “sustainable”, i.e. “meeting the needs of the present without compromising the ability of future generations, to meet their own needs, and thereby supporting long-term ecological balance” (as defined by the Brundtland Commission). Thus, architects must find solutions and strategies to make buildings sustainable regardless of their scale or function. Materials used in construction can provide architects the elementary ingredient in building more sustainably; materials that are cheap, easily available, and not harmful to the environment, ticking all the boxes of sustainability: economically, socially, and ecologically viable.
Thus, 10 such materials every architect must know about are as follows:
1. Natural Clay | Sustainable Materials
Finely grained natural rock or soil is known as natural clay, a material that has been in constant use in construction owing to its high plasticity, easy availability, and low cost. Clay is mostly used in the tiling of roofs and as a plaster, render paint, and flooring. It is known for its thermal insulation, robustness, durability, and fire resistance and as the primary ingredient in adobe, cordwood, rammed earth, etc.
2. Rammed Earth
Using compacted layers of aggregate, gravel, sand, silt, and a small amount of clay compressed within a formwork rammed earth is one of the oldest methods in construction by means of easily available material, i.e., earth. Rammed earth can be used to form walls, floors, and foundations, lending qualities such as load-bearing capacity, high thermal mass, low embodied energy, and almost complete reusability post demolition. It requires skilled labor to achieve the formwork but provides for architects to build using material on the site itself.
An evergreen perennial plant is known for its strength, hardness, and rate of growth; bamboo is one of the most popular sustainable building materials. It has a higher compressive strength than wood, brick, or concrete and a tensile strength that rivals steel, making it ideal for a variety of architectural use. Its versatility in construction from flooring to structure is only surpassed by its widespread use across the globe. From the temporary construction of bridges or scaffolding, bamboo has transitioned into a more permanent building material in recent times.
4. Straw bales
Straw bales are bundles of straw, a waste product from harvesting grains (wheat, rice, rye, or oats) that have been used in building for centuries. Bound together, they can be used as building insulation and to form load-bearing structural elements in construction. With wire mesh and wooden pins followed by stucco or plaster, the formwork of the straw bales makes for thermally insulated wall systems reducing the need for mechanical heating or cooling. However, straw bale construction is prone to moisture and mold; hence, it is not suitable in wet conditions.
5. Adobe | Sustainable Materials
Adobe, mostly used as a building material in the form of bricks, is a composite of earth, clay, straw, and/or other organic materials. Adobe bricks have similar properties to that of rammed earth construction with high thermal insulation and energy efficiency. Such bricks are formed in open-cast molds and dried in the open air before being laid using earth mortar. Excess exposure to wet conditions can lead to damage, thus deep waves are used in adobe construction.
6. Recycled plastic
Recovered scraps of waste plastic reprocessed into different materials and products give new life to one of the biggest polluters of the world like recycled plastic. In construction, recycled plastic can be found in polymeric timbers, polycarbonate panels, polymeric tiling, and alternative building blocks like EcoBricks or RePlasts, machine-compressed single-use plastic blocks. Currently, recycled plastic products are only used in small-scale construction but new architectural solutions are being developed.
7. Cross-laminated timber
CLT or Cross-Laminated Timber is composed of wood (usually from reforestation) sawn, glued, and layered as planks each perpendicular to the previous lamella for structural integrity. Produced as panels of a varying thickness suitable for floors, roofs, walls, and furniture, CLT is a versatile prefabricated material ideal for almost all sorts of architectural ideas. Although it is not cheap, it owes its sustainability to the rapid construction and renewability of the material.
An iron-based binding compound made using waste steel dust and silica from ground up glass reacting with carbon dioxide; ferrock is a carbon-negative material developed as a substitute for concrete. It is stronger and more flexible than Portland Cement and can be used in construction in similar applications. Although not yet viable for large-scale applications, due to the sourcing of waste materials, it proves to be one of the most sustainable in small-scale projects.
Mycelium is the rootlike fibrous underground growth of fungi that hold together the soil into a dense network for sprouting mushrooms. Construction applications of mycelium include composite boards (Mycoboard, a medium-density fibreboard), bio fabricated furniture, composite bricks, and organic sculptures using controlled growth of the fibers. Mycelium biocomposites are insulative, compostable, CO2 absorbing, and have high compressive strength. However, they are susceptible to termite infestation, and being relatively new, the material is still being researched in different conditions and applications.
10. Hempcrete | Sustainable Materials
A bio-composite material of hemp, the balsa wood-like core of a cannabis plant, lime, and water called hempcrete or hemplime, is an alternative to concrete and traditional insulation. Lightweight and durable, hempcrete is not suitable for load-bearing elements and needs a framework and finishing for installation. Being a plant product and with lime turning to limestone, hempcrete has a negative carbon footprint.
Being sustainable in architecture is no longer a choice but an imperative. Architects, responsible for shaping the built must add ten more, a hundred more materials and strategies to build a sustainable future.