The Complete Guide to Understanding Embodied Carbon

With the building industry striving for greater sustainability, embodied carbon has emerged as a crucial metric to address. But what exactly is embodied carbon, and why is tackling it so important? This comprehensive guide provides an in-depth look at embodied carbon, from primary sources to reduction strategies.

Key Takeaway

Embodied carbon, accounting for 11% of global energy-related carbon emissions, is crucial for achieving sustainable, net-zero carbon buildings. Reduction strategies include choosing low-carbon materials, reusing structures, optimizing design, and embracing passive building strategies.

 

 

What is Embodied Carbon 

Embodied carbon refers to the greenhouse gas emissions associated with building materials over their entire lifecycle. (The Carbon Leadership Forum) This lifecycle includes:

• Extraction of raw materials like concrete, steel, timber, and aluminum
• Energy-intensive manufacturing and refining processes
• Transportation of materials to the construction site
• The construction process itself 
• Maintenance, repairs, and replacements during the life of the building
• Demolition and disposal at end of life

Understanding the concept of embodied carbon is crucial when we consider the broader picture of carbon emissions in the building sector. Buildings are associated with two main types of carbon emissions: embodied carbon and operational carbon. Operational carbon emissions come from the energy used by buildings, such as heating, cooling, and powering them. In contrast, embodied carbon emissions are associated with the materials and construction processes used to build the buildings. These emissions are 'locked in' once construction is completed.

According to data, buildings account for 39% of global energy-related carbon emissions. Of this, 28% comes from operational emissions, and the remaining 11% from embodied carbon emissions, which are related to materials and construction. (NBI)

In the building sector specifically, embodied emissions make up a significant portion of all carbon emissions. As strategies to reduce operational carbon emissions become more effective, the proportion of embodied carbon emissions is expected to increase. This is because while operational carbon can be reduced over time with energy efficiency measures, embodied carbon is embedded in the building from the moment construction is completed.

Therefore, to achieve true sustainability in the building sector, addressing embodied carbon emissions is essential. These emissions, which are often overlooked, represent a crucial area where we can make significant strides in reducing our overall carbon footprint.

Major Sources of Embodied Carbon

The main sources of embodied carbon in building structures are (RMI):

1. Concrete - The cement production process is highly emissions-intensive, giving concrete a very high carbon footprint. Globally, concrete stands out as the construction material that contributes the most to emissions, accounting for the largest share of greenhouse gases released during the production and use of building materials.
   
   
2. Steel - Producing virgin steel is energy and carbon-intensive. The emissions add up with steel's widespread use. 
   
   
3. Aluminum - A carbon-intensive material compared to alternatives, aluminum is common in windows, cladding, and components.
   
   
4. Plastics - Plastics production emits greenhouse gases, and most plastics are carbon-intensive. They are ubiquitous in pipes, wires, finishes, and insulation.
   
   
5. Glass - Manufacturing glass requires high heat, often from carbon-based energy sources, leading to emissions.
   
   
6. Insulation - Some types of insulation, like petroleum-based foam boards, have high embodied carbon.
   
   
7. Timber - Sustainably sourced mass timber can have low embodied carbon, but processing and adhesives still add emissions.

Why Building Professionals Should Focus on Embodied Carbon

Architects, engineers, and contractors have several compelling reasons to prioritize embodied carbon (RPS). One of the most significant is the goal of achieving Net Zero Carbon Buildings. As operational emissions decrease due to efficiency gains, embodied emissions, which account for a larger share of overall lifecycle emissions, become increasingly important. Addressing embodied carbon is, therefore, critical for creating truly net zero-carbon structures

In addition to this, government policy drivers are emerging that focus on embodied carbon. Regulations such as Buy Clean procurement policies and low-carbon concrete codes are starting to limit embodied emissions. This means that building professionals need to prepare now for a policy landscape that will increasingly focus on embodied carbon.

Prioritizing embodied carbon also offers the chance to gain a competitive edge. Firms that proactively reduce embodied carbon will be ahead of the curve as these new regulations spread. This also gives manufacturers of low-carbon products an advantage in the market.

The health and well-being benefits of prioritizing embodied carbon should not be overlooked either. Many conventional building materials emit harmful pollutants during manufacturing, so using low-embodied carbon materials can enhance both indoor air quality and the health of building occupants.

Finally, focusing on embodied carbon can lead to significant cost savings. More efficient structural designs that use less material can greatly reduce costs. Furthermore, many low-carbon alternatives are already cost-competitive with conventional options, making them a smart choice economically as well as environmentally.

Strategies for Reducing Embodied Carbon

Multiple proven strategies exist to substantially cut embodied carbon without increasing building costs significantly (RMI):

Choose Low-Carbon Structural Materials - The bulk of embodied carbon comes from core structural components. Mass timber, green concrete with slag or fly ash, and recycled steel are lower-carbon alternatives.

Reuse Existing Structures and Materials - Renovation and adaptive reuse almost always have dramatically lower embodied carbon compared to new construction. Salvaged materials also have lower emissions.

Use Fewer Materials and Finishes - Optimizing structural designs to use less material overall is highly effective. Exposed ceilings and polished concrete instead of floor finishes also reduce embodied carbon. 

Specify Materials with EPDs - Requiring Environmental Product Declarations allows assessment and comparison of materials' embodied carbon footprints.

Prioritize Low-Carbon Products – Avoid carbon-intensive materials like plastics and switch to low-carbon alternatives.

Design for Deconstruction – Choosing connections and assemblies that are easy to disassemble and reuse at end of life reduces waste and new material demands.

Passive Building Design Strategies

Incorporating passive approaches in building design can lead to additional embodied carbon savings (RMI). High levels of insulation, when combined with air sealing, can significantly reduce heating and cooling loads, enabling the downsizing of HVAC systems. Strategic window placement is also a crucial aspect, as it maximizes the use of daylight and passive solar heat gains, thereby decreasing the need for artificial lighting and HVAC systems. 

Effective shading further complements these strategies by controlling solar heat gain, which in turn reduces the demand for cooling. Natural ventilation, facilitated by operable windows and vents, can minimize the need for mechanical ventilation, depending on the climate. 

Finally, considering the form of the building itself can contribute to embodied carbon savings. Compact shapes with a low surface area to volume ratio not only reduce heat loss but also require fewer materials, leading to further reductions in embodied carbon.

The Path Forward

Addressing embodied carbon will require unprecedented collaboration across the entire building sector (NBI). Each player has a crucial role to play:

• Governments must show leadership through bold policies like procurement standards and embodied carbon caps. Financial incentives for low-carbon projects are also critical to accelerate change.
  
  
• Architects, engineers, and contractors should take responsibility to proactively reduce embodied carbon. This includes learning about new materials and lifecycle analysis tools, optimizing designs, and preparing for expanding regulations.
  
  
• Manufacturers and suppliers need to respond to the demand for greener options by investing heavily in product innovations and processes that cut carbon footprints. Transparent EPD disclosures are vital.
  
  
• Developers hold the power to insist on low-carbon materials and designs from the very start of their projects, sending a strong market signal.
  
  
• Advocacy groups must continue refining practical strategies, voluntary programs, and educational resources that enable embodied carbon reductions.

With climate goals urgent, addressing embodied carbon is imperative. Though challenges exist, solutions from materials science to passive design are real and feasible. Collective action starting now across the building sector can set us on the path to low-carbon construction. The health of our planet depends on it.

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