In order to start integrating embodied carbon studies into projects to meet sustainability goals, it is important to consider many factors such as carbon (kgCO2e) values, and what typical ranges of values to be aware of when designing for embodied carbon reduction. This e-book presents an overview of how to start integrating embodied carbon studies in your projects.
Why Calculate Embodied Carbon in the Early Stages of a Project?
Annually, the embodied carbon of building structure, substructure, and enclosures are responsible for 11% of global GHG emissions and 28% of global building sector emissions. Between 39%-80% of a building’s total Carbon Footprint is a result of the embodied carbon from building materials. If evaluated early in the design phase, 80% of a building’s embodied carbon can be reduced.
The Paris Agreement, signed in 2016, is an agreement within the United Nations Framework Convention on Climate Change (UNFCCC), on issues climate change mitigation, adaptation, and finance. The Paris Agreement's long-term temperature goal is to keep the rise in global average temperature to well below 2 °C (3.6 °F) above pre-industrial levels; and to pursue efforts to limit the increase to 1.5 °C (2.7 °F), recognizing that this would substantially reduce the risks and impacts of climate change. KgCO2e emissions play an important role in the global climate crisis. Without reducing the embodied carbon within buildings, there is no chance of meeting The Paris Agreement's goals. Below, is an excerpt from an Embodied Carbon Summary Report by the Carbon Leadership Forum.
How to find Embodied Carbon values?
Building assemblies are layers of products, and each layer has an embodied carbon quantity. Collectively these products contribute to the climate crisis in a big way, but to understand a more accurate value of its impact, each product needs to be considered individually. The following hierarchy of data types provides the most accurate information for an Embodied Carbon study:
- From the EC3 database (or similar)
- Environmental Product Declaration (EPD)
- The median kgCO2e value for the product type based on known industry values
The Embodied Carbon in Construction Calculator (EC3) tool, is a platform that helps professionals find, assess, and reduce the amount of kgCO2e used in construction. EPDs are a standardized assessment of a product or building system’s effect on the environment. EPDs can be manufacture provided or a certified industry EPD. The third data type, the median kgCO2e value, is the focus of cove.tool's end-to-end automated performance analysis services.
Which Embodied Carbon Values Are Most Important?
Traditionally, an embodied carbon analysis can be one of the most time-intensive studies to undertake. The challenge of an Inventory analysis (featured below) is the number one deterrent for running an embodied carbon study. If there is not ample time to evaluate each element in greater detail, the best approach is to start with the largest contributors of embodied carbon by building component category and move downwards from biggest to smallest impact. Understanding where to start, based on a building's design features, is crucial.
The relationship between capital cost and embodied CO2e emissions are influenced by the characteristics of each building making optimization essential for each project.
- For low-rise buildings, embodied CO2e emissions are dominated by external walls, slabs, and foundations (Oldfield, 2012; Sansom and Pope, 2012).
- For medium to high-rise buildings, embodied CO2e emissions are dominated by floors and building frames (Sansom and Pope, 2012).
A study by Takano et al. (2014) showed that of all the total elements of a building, internal wall components like insulation and sheathing, surface materials like cladding or flooring, and the structural frame were the most influential on embodied carbon. The reasoning for this is concluded to be a product of the extensive use of concrete and steel, which are both carbon-intensive materials. Industry professionals can use this knowledge to their advantage with the cove.tool optimization inputs, to focus on critical building products with the highest EC impact.
Excerpt from Embodied Carbon Emissions of Buildings: A case study of an apartment building in the UK
The Takano study asserts that the External Walls and Roof components make up 41% of GHG emissions and roughly 52% of the building’s capital costs. This is a result of the material’s uses (insulation, concrete, and steel) and the proportion of those building elements compared to the remaining elements. This means that just 36% of the total building elements can make up to 80% of the embodied carbon of a building.
Conclusions
With this information, a logical approach is to begin collecting embodied carbon data for structural framing and support structures. These categories are the most significant in understanding the total embodied carbon footprint and being able to significantly reduce a building’s total output. It is also beneficial to begin creating internal documents with local and commonly used structural products and recording their embodied carbon values so that whenever a similar study is conducted by a building team, the values can be quickly repeated.
Priority For Low-Rise Buildings:
- Structural Framing (Envelope Tab - Wall Insulation)
- Exterior Walls (Envelope Tab - Glazing)
- Floor & Foundation (Structure Tab)
- Roof (Roof Tab)
- Others (Interior Finishes Tabs)
Priority For Mid-Rise To High-Rise Buildings:
- Structural Framing (Envelope Tab - Wall Insulation)
- Support Structure (Structure Tab)
- Floor & Foundation (Structure Tab)
- Roof (Roof Tab)
- Others (Envelope - Glazing & Interior Finishes Tabs)
Embodied Carbon Values by Material Category
Each project is unique and should undergo a full life-cycle analysis for an accurate understanding of embodied carbon throughout its life-cycle. However, a standard range of embodied carbon can help to understand early design implications as predictive insight for a project. Conducting a carbon analysis can have a huge impact, even if calculated values differ by 5% to 10%. Values within the conservative or median range are recommended for early design models at a high level to help narrow product categories down to a single preferred category. Products within each category can then be further explored with product-specific values in cove.tool during the design development phases.
The EC3 database provides ranges for each material category and sub-categories from its compiled EPD database. It is a tool for extracting a consensus of existing products to help clarify which products offer minimum embodied carbon impact.
Understanding Embodied Carbon Values
The following list is a snapshot for each category provided to help identify a conservative embodied carbon value for each building component category.
- Conservative Range - the Embodied Carbon typical range of 60%-80% of known products in the category as conservative (upper value) and achievable (lower value).
- Max/Min - Maximum and minimum of all EPDs based on EC3’s 80% confidence estimate.
- CLF Baseline - the Carbon Leadership Forum derived baseline for the category.
More information on EC3 and cove.tool are discussed here.
