Building materials have a major impact on the environment. Their creation, processing, and transportation require a lot of energy and emit greenhouse gases.
Innovative solutions reduce the embodied carbon of common construction materials. One example is replacing cement, which accounts for 8% of all emissions, with a concrete mix that uses waste slag and draws CO2 from the air to make it carbon negative.
CLT
Building with wood isn’t a new phenomenon, but cross-laminated timber (CLT) has emerged as a popular and sustainable alternative to concrete and steel. This mass timber product is a structural building material that is made from layers of wood boards stacked in alternating directions, then bonded together with a structural adhesive. It can be used to form floors, walls and roofs for buildings up to 18 stories.
It’s a carbon-neutral construction material because it uses renewable, low-carbon wood from responsibly harvested forests. CLT production is also energy-efficient, generating less greenhouse gas emissions than concrete and steel. And when combined with an on-site energy efficiency strategy, CLT can help a building reach net zero status.
One of the major benefits of using CLT is its prefabricated nature, which allows builders to cut construction time. This is because the panels can be assembled offsite and delivered to the job site in large sections, allowing for faster installation. For example, Waugh Thistleton Architects built the Dalston Works in London, a CLT-built office and retail space, in just eight weeks.
Additionally, CLT is more resilient to seismic forces than other construction materials. According to Kelley, the insulating properties of CLT can help prevent heat from escaping a building during an earthquake, so it will retain its structural integrity. Further, when it comes to fire resistance, CLT is a natural fire retardant and can be treated with additional chemicals to improve its performance.
Wood
Using carbon-negative building materials is vital to reduce greenhouse gas emissions. These new innovations can actually remove more carbon from the atmosphere than they emit during construction. Additionally, they are more resilient against seismic and climate conditions than traditional materials. This allows builders to save on energy expenses, and tenants to enjoy a greener environment.
Most common construction materials have a serious impact on the environment. These materials need to be processed from their raw states, which requires a lot of energy. The production of these materials and their transportation to the build site also emits a large amount of carbon dioxide.
Wood is an environmentally friendly material that is becoming more popular. However, it is important to ensure that the wood is sourced from a sustainable source. Illegal logging destroys vast natural carbon sinks and causes irreversible damage.
The main components of wood are carbon, oxygen, and hydrogen. It also contains a small amount of sulfur, chlorine, nitrogen, potassium, sodium, magnesium, iron, and manganese.
Unlike concrete, which is one of the leading carbon-intensive construction materials, wood is a renewable resource. It can also be recycled. In addition, wooden framing is lighter than concrete blocks and can be transported to the build site easily. This reduces transport costs and construction time. Wood also has thermal insulation properties that are better than any other mainstream building material.
Insulation
Insulation is a key part of the building envelope that contributes significantly to reducing a building’s net energy demand. Consequently, insulation materials play a decisive role in meeting carbon neutrality targets. As a consequence, reducing the embodied carbon of insulation materials is one of the main goals of the research community in the area of carbon-neutral construction materials.
There are several options for achieving carbon-neutral insulation:
These range from bulky fiber materials such as fiberglass, rock wool, and cellulose to sleek foils. Bulky materials trap air or another gas in their cells to resist conductive heat flow, while foils reflect radiant heat away from living spaces. In addition, a growing number of insulation products are being made from recycled paper or post-consumer waste to reduce their environmental impact.
To achieve a carbon-neutral result, the material must absorb more CO2 than it releases during its life cycle. Some manufacturers are experimenting with carbon-negative insulation by using biochar, which captures and stores carbon dioxide. Others are focusing on innovative construction techniques, such as London start-up Seratech’s method of combining traditional concrete with silica produced from captured industrial emissions and the carbon-absorbing mineral olivine.
Other manufacturers are aiming to cut the embodied carbon of their insulation by making it from post-consumer waste or bamboo, which grows much faster than conventional wood and reduces deforestation. Still, most efforts focus on minimizing the embodied carbon of structural elements and leveraging prefabricated insulation panels that can be used for wall, floor, roof, and ceiling applications.
Metals
As the construction industry seeks new ways to achieve carbon-neutral buildings, some companies are using building materials to help sequester and store carbon. These technologies could be used in deep energy retrofits and building new homes to decrease net emissions and transform buildings into climate assets.
The embodied carbon in building materials accounts for a significant portion of the total greenhouse gas (GHG) footprint from a building, and it’s one of the biggest challenges to reaching a low-carbon economy. Many companies are developing innovative solutions to reduce a building’s embodied carbon, including reducing the amount of concrete, steel, and aluminum.
Some companies are experimenting with bio-based cements that can absorb CO2. For example, Montreal-based Carbicrete uses a limestone substitute, and the company captures the carbon dioxide released during the manufacturing process and injects it into the product to create a carbon negative concrete.
Other companies are using mycelium, the roots of fungi, to make carbon-negative building insulation. The product was recently used to clad a German car dealership, and the material is naturally fire-retardant and stores 14 tons of carbon per month.
Other carbon-neutral construction products include timber frame walls, which can be pre-fitted together and shipped to a build site, reducing the need for more energy-intensive materials like steel. Also, Kedel’s external cladding is made from recycled high-density polystyrene that otherwise would have been thrown away, and Gutex produces an exterior thermal insulation system that requires less energy to manufacture than traditional alternatives.