A monthly exploration into the world of sustainability in the built environment with commentary and input from UCEM’s Principal and academics.
What is embodied carbon (and what can we do about it)?
Posted on: 13 November, 2023
Reducing the amount of embodied carbon created in the construction process is one of the biggest challenges facing the built environment.
The built environment has a pivotal role to play in the battle against climate change. Our sector is responsible for around 40% of global CO2 emissions annually, and despite new innovations in the construction process like adaptive reuse and prefabrication, we still have a work to do if we want to achieve the 2050 net zero target set out by the United Nations.
To truly address our environmental impact as a sector, we need to do more than turn to external activities like carbon offsetting – we need to review the processes and practices in the construction lifecycle and look for new, sustainable alternatives.
One of the biggest talking points and most common challenges in the mission to realise a sustainable built environment is the topic of embodied carbon. But what exactly is it, and what can be done to reduce it?
What is embodied carbon?
Embodied carbon is the greenhouse gas emissions that are created in the construction lifecycle before a building becomes operational. Some of the processes that produce embodied carbon include the manufacturing, transportation, installing and removing of construction materials. It also includes the emissions created in the maintaining, demolition and disposal of waste from a demolished building.
How to calculate embodied carbon emissions
Embodied carbon is in essence the carbon footprint of a material, or cumulatively, a building. To calculate embodied carbon, multiply the quantity of the material (e.g. steel or concrete) by its carbon factor – the amount of carbon released in the creation/production of the material up to this point.
The difference between embodied carbon and operational carbon
While embodied carbon is the emissions produced by the construction of a building pre-operation, operational carbon is the emissions that then arise from its use and from things like heat, energy and lighting.
Why is tackling embodied carbon so important?
Thanks to new innovations and technological advancements, the amount of operational carbon emissions produced by buildings has decreased, meaning the focus has moved to dealing with embodied carbon. By current estimates, embodied carbon is a significant contributor to the built environment’s impact on climate change, accounting for around 10% of global energy-related CO2 emissions. This is why it’s become so prevalent in sustainability discourse – if we want to achieve net zero as a sector, we need to address the carbon emissions we produce throughout the entire construction life cycle.
The benefits of reuse and renovation aren’t restricted to sustainability, either. Techniques like adaptive reuse can reduce your construction costs, optimise energy consumption, accelerate the time to completion of your project and go a long way to reducing urban sprawl.
If you can’t reuse an entire building or its foundation, what about reusing materials from it instead? Salvaged materials from previous developments such as brick, metal, concrete or wood are likely to have a lower embodied carbon footprint than any new materials you manufacture for a project, as the carbon involved in their creation has already been utilised and you don’t need to use more carbon to produce them.
3. Perform life cycle assessments
A life cycle assessment is where a building’s total environmental impact is quantified. While this can be applied at any stage of a building’s life cycle, it’s often done in the planning phase to identify any potential environmental issues around construction. Doing this early on can help you avoid using problematic materials and identify opportunities where you can use more sustainable materials – all of which can reduce the embodied carbon footprint of your project.
4. Limit materials with high carbon footprints
Certain materials like concrete, steel, aluminium, plastic and forms of insulation are high in embodied carbon. Another quick win is to limit their usage and instead turn to more sustainable alternatives.
5. Turn to low-embodied-carbon building materials
As mentioned above, reusing existing materials is a great option, but if that isn’t viable for your project, there are new, alternative materials you can use with lower embodied carbon. For example, instead of foam insulation you can use hemp or straw, while wood can be a great alternative to concrete or steel.
6. Optimise structural efficiency
The high footprint of materials like concrete and steel mean that most of the embodied carbon you’ll find in a building belongs in its structure, making it a prime target for optimisation through things like wood framing.
7. Minimise waste
Embodied carbon doesn’t just account for the emissions from the beginning of your project – it also includes the end of a building’s use, its demolition and the waste from these processes, too.
8. Utilise carbon sequestering materials
Carbon sequestration is a naturally-occurring process where carbon dioxide from the atmosphere is captured and stored. Using carbon-sequestering materials like wood, straw and hemp in your construction project can go a long way to reducing embodied carbon levels.
9. Use high-recycled content materials
Non-recycled materials have significantly higher carbon footprints than their recycled counterparts. For example, virgin steel can have five times as much of an embodied carbon footprint than high-recycled content steel.
10. Consider prefabricated or modular construction
Prefabrication is the method of creating and producing components of a building off site and then delivering them to the project for them to be quickly assembled. This can help accelerate building projects and provide cost-saving opportunities, but most importantly prefabrication techniques have implications for sustainability and embodied carbon, too, as it can reduce the amount of waste from a building site.
Modular construction – the creation of standardised and repeated sections of buildings that can be quickly pieced together – can in particular reduce the amount of waste resulting from the production of materials thanks to the simple and repetitive nature of their design.
Sustainability isn’t a passing trend – it’s here to stay and is constantly evolving. If you want to inspire and action change in your career, UCEM’s MSc Innovation in Sustainable Built Environments will give you the skills you need, both now and in the future.