This article presents an overview of how to choose which Embodied Carbon (kgCO2e) value to use and what typical ranges of values to be aware of when designing for Embodied Carbon reduction. Skip to the end of the article to get typical values and which items have the biggest impact.

Why calculate embodied carbon in the early stage? 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. There is no chance of the world meeting the Paris Agreement without buildings reducing embodied carbon. Below, an excerpt from an Embodied Carbon Summary Report by the Carbon Leadership Forum.

**Read the related articles on Embodied Carbon and cove.tool, and Structures and Interior Finish for Embodied Carbon Optimization to understand better the importance of Embodied Carbon and the terminology of building products associated with it.

How to find Embodied Carbon values?

Building assemblies are layers of products that each 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. A hierarchy of data types to provide the most accurate information for your Embodied Carbon study.

  1. Directly from the EC3 database (or similar).
  2. A manufactures certified product EPD
  3. A certified industry EPD
  4. The median value for the product type from known values

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 (ex. below) is the number one deterrent for running an embodied carbon study. If there is not time to look at everything, the best approach is to start with the largest contributors of Embodied Carbon by building component category and move down the from biggest to least impact. This section provides a general guide of where to start, based on your building design.

(Above) Diagram for Inventory Analysis for LCA. Khasreen, Monkiz & Banfill, Phillip & Menzies, Gillian. (2009). Life-Cycle Assessment and the Environmental Impact of Buildings: A Review. Sustainability. 1. 10.3390/su1030674.

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 CO2-e emissions are dominated by floors and building frames (Sansom and Pope, 2012).

A study by Takano et. al (2014) showed that of the three-building components of the structural frame, internal wall components like insulation and sheathing, and surface materials like cladding or flooring, the structural frame was the most influential on embodied carbon. The conclusion for this is its extensive use of concrete and steel, both carbon-intensive materials. Users can use this knowledge with the cove.tool optimization inputs to focus on critical building products with the highest EC impact.

(Above) Excerpt from Embodied Carbon Emissions of Buildings: A case study of an apartment building in the UK

From the Takano study, we can gather 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 materials uses (insulation, concrete, and steel) and the proportion of those building elements compared to the remaining elements.

Just 36% of the total building elements can make up to 80% of the embodied carbon of a building. One case study compared two building types, a three-story Apartment Building, and a Mid-Rise Office tower.

(Above) Adapted from Embodied Carbon Emissions of Buildings: A case study of an apartment building in the UK

Conclusions

With this information, a good rule of thumb approach is to start collecting embodied carbon data for structural framing and support structure. Having just these categories can be a significant boost in knowing your Embodied Carbon footprint and being able to significantly reduce your building's total. Another useful tip for getting started is creating internal documents with commonly used structural products in your area and their Embodied Carbon values, so whenever a similar study is conducted by your team, it can be quickly repeated. We are working on making this automated as well so feel free to share any resources you find from local supplies with us!

Priority for Low-Rise buildings:

  1. Structural Framing (Envelope Tab - Wall Insulation)
  2. Exterior Walls (Envelope Tab - Glazing)
  3. Floor & Foundation (Structure Tab)
  4. Roof (Roof Tab)
  5. Others (Interior Finishes Tabs)

Priority for Mid-Rise to High-Rise buildings:

  1. Structural Framing (Envelope Tab - Wall Insulation)
  2. Support Structure (Structure Tab)
  3. Floor & Foundation (Structure Tab)
  4. Roof (Roof Tab)
  5. Others (Envelope - Glazing & Interior Finishes Tabs)

Embodied Carbon values by Material Category

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. An example and breakdown of what the chart is provided as a reference.

Each project is unique and should undergo a full life cycle analysis for an accurate understanding of embodied carbon throughout its full lifecycle. However, a standard range of Embodied Carbon can help understand early design implications as predictive insight for a project. Do not sweat over the details since doing this study has a huge impact even if its off by 5% to 10%. Values within the conservative range or its median value is recommended for early design models to help narrow product categorize at a high level down to a preferred category. Products within that category can then be further explored with product specific values in cove.tool during design development phases.

Understanding Embodied Carbon values:

  • 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

The following list is a snapshot for each category provided to help identify high or low, conservative Embodied Carbon value for each building component category. More information on EC3 and cove.tool is discussed here.

Concrete

  • Conservative Range: 296 - 454 kgCO2/yd3
  • Max/Min: 31.7 - 1160 kgCO2/yd3
  • CLF Baseline: 489 kgCO2/yd3

Steel

  • Conservative Range: 0.433 - 0.795 kgCO2/lbs
  • Max/Min: 0.279 - 1.84 kgCO2/lbs
  • CLF Baseline: 1.36 kgCO2/lbs

Aluminum

  • Conservative Range: 2.52 - 4.01 kgCO2/lbs
  • Max/Min: 1.47 - 6.73 kgCO2/lbs
  • CLF Baseline: 8.16 kgCO2/lbs

Wood - Dimensional & Prefabricated Products (Truss, Wood I-Joists, Framing)

  • Conservative Range: 34.8 - 172 kgCO2/yd3
  • Max/Min: 12.6 - 367 kgCO2/yd3
  • CLF Baseline: 430 kgCO2/yd3

Wood - Sheathing Panels

  • Conservative Range: 67.4 - 197 kgCO2/yd3
  • Max/Min: 12.6 - 345 kgCO2/yd3
  • CLF Baseline: 306 kgCO2/yd3

Insulation

  • Conservative Range: 0.14 - 0.562 kgCO2/ft2
  • Max/Min: 0.0236 - 12.4 kgCO2/ft2
  • CLF Baseline: 0.983 kgCO2/ft2

Glazing (insufficient data)

  • Conservative Range: 0.441 - 0.619 kgCO2/lbs
  • Max/Min: 0.441 - 0.886 kgCO2/lbs
  • CLF Baseline: 1.59 kgCO2/lbs

Finishes - Gypsum Board

  • Conservative Range: 0.246 - 0.531 kgCO2/ft2
  • Max/Min: 0.110 - 1.320 kgCO2/ft2
  • CLF Baseline: 0.418 kgCO2/ft2

Finishes - Ceiling Panels

  • Conservative Range: 0.443 - 1.03 kgCO2/ft2
  • Max/Min: 0.11 - 2.78 kgCO2/ft2
  • CLF Baseline: 2.79 kgCO2/ft2

Finishes - Carpet

  • Conservative Range: 0.568 - 1.25 kgCO2/ft2
  • Max/Min: 0.11 - 2.19 kgCO2/ft2
  • CLF Baseline: 3.25 kgCO2/ft2

Related help articles:

Embodied Carbon and cove.tool

Understanding Embodied Carbon values for building products in cove.tool

Structures and Interior Finish for Embodied Carbon Optimization

Designing for Net-Zero Energy and Net-Zero Carbon

Embodied Carbon calculation for wall framing in cove.tool

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