The UK government has set a goal to reach a Net Zero economy by 2050, achieving a 78% reduction by 2035.
As it makes up 39% of all energy-related carbon emissions (UN Environmental & the International Energy Agency), the construction industry will be under pressure and increasing regulation to lower its carbon output. This means that considering the emissions of your next construction project will be a crucial part of your planning and risk mitigation.
You may be considering methods such as carbon offsetting to decrease the overall carbon output of your next build. However, carbon offsetting is not a long term solution. Mathematically, it is not possible to use these methods to account for the amount of carbon emitted by the construction industry. As a result, to achieve the government set carbon emissions targets, it will be necessary for the construction industry to adopt new green alternatives to typical materials.
This article outlines some examples of low-carbon, carbon neutral and carbon negative materials, highlighting exciting innovations within our industry. It will provide you with ‘swaps’ and long-term solutions to reduce your project’s operational and embodied carbon output. It also considers the broader construction capabilities of each material. This will help you mitigate the risk of stricter carbon targets and put your project ahead in the inevitable move towards a greener construction industry.
Concrete and cement significantly contribute to the carbon footprint of the construction industry.
In particular, cement alone has been estimated to solely account for between 5 – 10% of all greenhouse gas emissions. That’s the equivalent emissions of all the cars in the United States and half of those in Europe (Geopolymer Tech 2021). This is significant as cement is a key ingredient in concrete, the second most consumed material in the world (after water!).
The reliance of the construction industry on such carbon-intensive materials will be a significant roadblock to reducing the sector’s carbon footprint. However, exciting innovations in concrete and cement alternatives can solve this issue.
Imagine if the building blocks of your house didn’t add anything to your carbon footprint. Or better, what if they actively reduced the total embodied carbon of your project?
The first scenario could be achieved by using spheraZero, the first-ever carbon zero dense aggregate concrete block. This means the use of this material adds no carbon output to your project. By comparison, a traditional dense block contributes 0.062 tonnes (62kg) of CO2eq per tonne of blocks used (CBA Dense Block EPD). By replacing standard concrete with spheraZero, you could significantly reduce your build’s carbon output.
For a step further, there’s spheraLite, the world’s first carbon-negative aggregate concrete block. It’s a lightweight building block with a carbon footprint of -0.16 tonnes (-160kg) CO2eq per tonne. As a result, it actively reduces the footprint of your build.
To put that into practice, if you were building ten typical three-bed houses, you could save 72 tonnes of CO2 using spheraLite and spheraZero. That’s the same as thirteen years of electricity to power each home or planting 1200 trees.
Carbon negative: As a carbon-negative construction block, spheraLite can immediately reduce your building’s carbon footprint. This can help to counteract unavoidable emissions elsewhere in your build. Due to the limited innovation within the sector, carbon output from other elements of the building process may be inevitable. Therefore, introducing carbon-negative materials will be a necessary, long-term solution to reduce your total carbon emissions or even achieve Net-Zero.
Operational carbon: With a comparatively low thermal conductivity, the blocks will save energy once in use. Therefore, Sphera products also support a reduction in the operational emissions of your building (the carbon emitted during the building’s occupation).
'In summary, Sphera’s blocks are able to reduce the carbon associated with a build and reduce operational carbon when compared to typical blocks.
Regen is a cement substitute using Ground Granulated Blast furnace Slag (GGBS).
Regen typically replaces 50% of Portland cement in your concrete mix, which significantly reduces the embodied carbon of your concrete (the carbon emissions caused by the material’s manufacturing). Hanson estimates that one tonne of Regen produces just 0.07 tonnes of CO2eq (in comparison to 0.95 tonnes per tonne of typical Portland cement).
For example, by using a mix of 50% Regen in their concrete, 20 Fenchurch Street (otherwise known as London’s ‘Walkie Talkie’) achieved an ‘Excellent’ BREEAM rating, a type of built environment sustainability score.
Circular economy: GGBS is created from a by-product of steel production. This circular approach means that Regen provides a longer-term solution to reduce the carbon emissions of your build in comparison to offsetting methods like tree planting.
Durability: Compared to Portland cement, Regen uses less calcium hydroxide and has a finer pore structure. It is less permeable, ultimately longer-lasting and a durable materials choice for your next build.
Although it doesn’t completely eliminate the carbon output of your concrete, using Regen can significantly reduce the overall carbon footprint of your project.
So concrete has a high global carbon footprint. However, counterintuitively it can also be considered a better alternative as it is often used to replace even more carbon-intensive products, such as traditional fired clay bricks.
Bricks are typically used to improve the aesthetics (looks) of construction projects such as houses and are available in a range of colours. However, using concrete as an alternative does not mean you cannot create a classic red-brick look. In fact, concrete bricks have a surprisingly wide range of available colours, such as white, black and even red.
“Due to the way we manufacture our products, they have significantly less embodied carbon than clay bricks – almost 50% less over their whole lifecycle,” Chris Harrop, Sustainability Director for Marshalls (Interview for Dezeen).
Carbonation: More and more the industry is recognizing the use of concrete to sequester (remove) carbon from the atmosphere. Typically, concrete bricks are used on the outside of buildings where they are exposed. This means that, over the lifetime of the building, the concrete absorbs carbon from the atmosphere, unlike traditional red bricks.
Durability: Not any old concrete can be exposed to the elements, due to a process called freeze-thaw. This is when small amounts of water inside a concrete brick/block can freeze in the winter and cause cracks.
By contrast, Marshall’s concrete bricks have been designed to withstand rain and frost. They have also passed the most rigorous freeze-thaw tests, designed to establish the durability classification for masonry.
In summary, Marshalls concrete bricks are as durable as traditional bricks, better for the environment and available in a wide range of colours.
Adequate insulation is a core part of the Climate Change Committee’s 2021 report on the sixth carbon budget (2033-2037). They found that 17% of greenhouse gas emissions are caused by buildings, primarily due to heating. This is significant as the UK’s legally binding Net Zero goal means ‘eliminating’ building emissions by 2050 (CCC UK Sixth Carbon Budget 2021).
Therefore, considering less carbon-intensive insulation to reduce your build’s operational (‘lived in’) emissions will be increasingly crucial.
When considering insulation alternatives, you may also want to consider fire safety, durability and efficient technical specifications (such as thickness).
Thermulon produce aerogel-based insulation – a material originally deployed by NASA to insulate in space.
As aerogels are mainly made up of air, they’re thinner and more insulating than more commonly used materials. Aerogels are also great candidates for using waste materials as precursors, contributing to a circular economy. As a result, novel aerogels are unlikely to add much to the embodied carbon output of your construction project.
Operational carbon reduction: Aerogels are more insulating than conventional materials like plastic or mineral wool (Ryder Architecture 2021). You can reduce your heating demand by 25% with just a 10mm layer of aerogel based insulation (Guinoa et al., 2017). Using this type of insulation can better reduce the energy needed to occupy the building and, therefore, the operational (‘lived in’) carbon output of your project.
Circular economy: Similarly to Sphera products, Thermulon is looking to use waste products (from construction) to create their aerogels.
Additionally, the aerogels themselves are very durable, meaning they can be reused and repurposed over time. This saves on waste and ensures the longevity of your project material choices.
Fire safety: One of the key promises made by Thermulon is that they will not compromise on fire safety. Their aerogel insulation can achieve an A2 fire rating, meaning it will be suitable for use in high-rise buildings.
Lower cost: It can be a relatively low-cost alternative. Their scalable method of creating insulation can reduce the cost of fire-safe, super-insulating aerogels fivefold.
Thickness: Compared to conventional products, Thermulon-based insulation can be very thin. It can therefore significantly increase the available floor area of your new build. This can be an especially lucrative attribute in tight-spaced city projects.
In summary Thermulon’s aerogel based insulation can be made thinner than typical insulation without sacrificing on thermal performance, fire-safety or cost.
Steel and concrete are the mainstream materials used in building structures. However, as we’ve discussed, using concrete in construction is a significant source of the industry’s carbon output. Moreover, the iron and steel industry is responsible for 5% of greenhouse gas emissions globally. In terms of carbon, one tonne of concrete emits half a tonne of CO2eq, and, even more shockingly, one tonne of steel can emit up to two tonnes of CO2eq (International Energy Agency 2016). Therefore, the continued heavy use of these materials in their current state is not compatible with the UK’s promise of Net Zero by 2050.
In short, these materials are highly carbon-intensive. Therefore, considering other structural alternatives could be important when ensuring your next construction project fits within future emissions regulations.
Timber is coming back into fashion as a low-carbon construction material. This is because trees remove and store carbon from the atmosphere as they grow. Additionally, they are sturdy and long-lasting enough to effectively replace carbon-intensive steel or concrete.
The Climate Change Committee’s 2018 report describes these benefits, stating that ‘government policies should assist a transition towards increased use of biomass in construction’ (CCC 2018). This report significantly promotes timber use in building due to its ability to sequester carbon during growing and provide an effective alternative to carbon-intensive materials used in the industry.
An excellent option for construction material wood is cross-laminated timber (CLT).
Cross-laminated timber is an engineered wood panel product and a ‘natural choice’ for construction that requires ‘low-embodied-carbon materials’ (Structural Timber Association). It also provides a durable and robust alternative for internal structures.
Solving the circular economy bottleneck: Although timber can be an environmentally sustainable choice, waste is still significant.
The UK produces 10 million tonnes of wood per year, worth £2.1bn. However, only 1 million tonnes of it is recycled. The rest goes to landfill (Veolia and Imperial College London 2019). This is due to contaminants like metal (such as nails) or treating chemicals that are too costly to remove to ensure recycling.
CLT is more straightforward to repurpose than alternatives such as plywood and medium-density fibreboard (MDF). It doesn’t use adhesives that then become toxic during recycling (like urea-formaldehyde).
Therefore, using timber, and more specifically CLT, is a strong, low-carbon alternative to two of the most carbon-intensive materials in the construction industry.
Bamboo is an increasingly popular construction material and a fast-growing, high-yielding and easily renewable natural resource (Institute of Civil Engineers 2017).
Unlike regular timber, which you can only harvest after 50+ years, bamboo has a much faster turnover of every 4-5 years. This means that it has quicker carbon sequestration and a higher volume of material potential.
Lamboo uses laminated engineered bamboo in heavy timber construction and glued laminated (Glu-lam) applications (Lamboo 2021). You can use it for interiors, exteriors and structural building needs. This includes everything from Glu-lam beams, to joists, to large outdoor structures.
A pleasing aesthetic: Lamboo comes in a range of attractive colours, so it doesn’t need any additional coverings to be aesthetically pleasing (e.g. drywall).
Density: The material is very dense, so appropriate for larger spans and longer beams.
You can use nearly all of it: You can use up to 99% of your Lamboo material which saves you time, money and resources cutting around defects and knots. This significantly reduces both financial and material waste.
However, it’s more expensive: Lamboo compares themselves in price to ‘exotic lumbers’ like IPE instead of typical timber alternatives. Therefore, the cost of this material may be a consideration when selecting it for your next structural project.
With concrete and steel being such a significant proportion of the carbon emissions produced by the construction industry, finding structural alternatives is the only practical method to reach Net Zero by 2050.
Biomass materials offer durable, low-carbon alternatives.