The construction industry is experiencing increasing demand to address climate change and remediate the enormous impacts the sector has had on the natural environment. Ensuring a healthy planet, vibrant and resilient communities, regenerating natural systems, and designing-out waste and pollution should be at the core of any sustainability framework.
The built environment contributes a substantial chunk of global CO₂ emissions, with the construction industry accounting for nearly 40% of global energy and GHG emissions. Some of the industry’s most popular materials, steel and concrete, contribute 7% and 8% of total global CO₂ emissions, respectively . The implications, reach, and magnitude of the impacts are well-researched, and it’s safe to say that the environmental impacts of construction are unsustainable.
Using more eco-friendly and recyclable materials in construction will require research, innovation, and new techniques and technologies. In our article listing the Top 10 ways to decarbonize the built environment, we concluded that a diverse range of inextricably connected approaches is required. One strategy that did stand out is to replace traditional materials with recycled, recyclable, or biobased materials; we’ve written articles on Hempcrete, Engineered wood, and High Strength Steel to showcase this. But the industry is constantly evolving, and the potential doesn’t stop there, so we’ve decided to explore more of these solutions by listing the top 5 most sustainable construction materials used.
1. Zero-carbon cement
Zero carbon cement is cement produced in a way that produces zero emissions. Portland cement has been a global standard in cement production since the early 19th century. Cement production is the world’s biggest industrial carbon pollution culprit, contributing to approximately 8% of global emissions, equivalent to all the cars on earth combined !
So, the time has come to rethink cement. Cement mostly acts as the binder between aggregates in forming concrete, yet it’s almost exclusively responsible for the resulting CO₂ emissions of concrete. But its affordable, durable, and versatile properties have made it the world’s second-most consumed substance after water .
The chemical reactions turning limestone into cement, the energy needed to produce high temperatures, and transportation costs must all be addressed. Alternative fuels, waste, or the electrification of kilns can drive out fossil fuels required to power cement production. The infrastructure used to transport cement can also be decarbonized. Substituting emitting ingredients in cement with alternative coarse and fine aggregates such as crushed rock sand, industrial by-products, glass, or plastics can make concrete more sustainable. Where cement is used, maximizing its efficiency should be top of mind through recycling and reuse.
2. Smart windows
Smart windows can help maximize passive design. In short, smart windows use specialized glass that adjusts their tint based on ambient temperatures. This allows them to retain heat during winter and dissipate heat during summer.
Smart window technology is not new; it’s been employed in airplanes, boats, and cars but is slowly making incursions into homes, offices, and airport terminals. Chemical reactions in smart windows between suspended particle devices, electrochromic materials, or polymer liquid crystals and heat or light levels are the secret to their color-changing properties. They can be the new secret to reducing energy consumption in buildings.
Perhaps one of the most promising materials in the charge towards sustainability goals is mycelium brick. Mycelium is a natural fungus material produced from the root-like fibrous material of fungi underneath the ground. When processed and dried, this natural material has industrial-level strength. Mycelium bricks can be grown when organic waste, like straw, is put into contact with mycelium. The fungus grows and digests the waste leaving behind a solid brick. It takes a few days, and all that’s required is waste at room temperature! It’s 100% organic, compostable, biodegradable, and fire and water-resistant, and its use as a building block for future buildings is promising. It has been used before for packaging purposes and in other disciplines, but its potential to be exploited as a building material in the construction industry is expanding.
While it may not have all the functional characteristics required for construction, such as high strength and durability, mycelium can be exploited for other functions like insulation. It can be used to create airtight insulation between wooden panels. Despite some limitations, there is excellent potential, so watch this space!
Timber as a commercial construction material is going mainstream; projects like the Atlassian Tower in Sydney, the world’s tallest hybrid timber tower, signal new heights and bold sustainable solutions using this natural material.
Bamboo is no exception; while it technically falls into the category of plant grasses, it can be harvested more sustainably and replenished quicker than any other timber. Also, in the way that it grows, it does not require pesticides, irrigation, or fertilizers. Some species can even grow up to a meter per day.
But what about its building properties? Bamboo has a high compressive strength and is an extremely lightweight material. Bamboo has a higher tensile strength than steel due to its axial fibres. Bamboo is substantially fire resistant and can withstand temperatures up to 4000 C due to its high silica content and water.
Bamboo is used to construct walls, partitions, flooring, and scaffolding, adding stability, strength, and protection. Bamboos are easy to install and highly cost-effective.
5. Recycled materials
Reusing, recycling, and repurposing materials automatically boost the sustainability credentials of any project. Steel is by no means an environmentally friendly material, and it is not renewable. However, it remains a lightweight, durable, and versatile material. The upside is that steel is multi-cyclable, which means it can be reused, repurposed, and pass through the supply chain in multiple forms almost indefinitely. Even after being recycled numerous times, steel keeps its original metallurgical properties. Recycling steel also means 75% less energy is used compared to making new steel products . Energy and natural resources are saved, and carbon emissions are reduced.
Similarly, recycling materials like rubber, which can be used for paving surfaces as granules in asphalt, also improve the sustainability quotient of many projects.
Finally, like recycled steel, timber, and wood can be reclaimed from old projects and reused in new ones. Salvaging wood from old structures such as buildings, barns, warehouses, bridges, or old forestry logs can be reused in other settings without reprocessing into a different product. Wood products can also be recycled through milling, cutting, coating, or sanding to create a new product. Growing momentum in preserving forests and reducing deforestation will only boost the appeal of reclaimed and recycled timbers.
Decarbonizing the construction industry is no easy task, and we recognize that many of the interdependencies that can make it happen will need to work together in harmony. But, we also know that the road to net zero will be bumpy if we don’t actively work towards making the building sector more sustainable.
-  CalcTree. “Ways to Reduce Embodied Carbon in Our Built Environment,” CalcTree Blog. https://www.calctree.com/blog/ways-to-reduce-embodied-carbon-in-our-built-environment.
-  Beyond Zero Emissions. "Rethinking Cement: Research Report", August 2017.
-  World Economic Forum. “A Net-Zero World Needs Net-Zero Concrete,” World Economic Forum Agenda, 8 July 2021.
-  Business Recycling. “Iron and Steel Recycling,” Business Recycling, 2022.