05. The Calculation - DavidVeld/CarboLifeCalc GitHub Wiki

This page will describe in-depth how the embodied carbon is calculated. Carbo Life Calculator uses the following resources and guidelines:

The following diagram shows how Carbo Life Calculator uses the volumes, and calculates it's embodied carbon:

We can write the process in four parts:

  • Definition of the material quantities, in kg.
  • Definition of the embodied carbon intensities, in kgCO2e/kg
  • Definition of the embodied carbon by combining 1 & 2
  • Include project and global defined costs

5.1 Definition of the material quantities

The material quantities can be gathered using the Revit plug-in or typed in directly into the carbon material groups. Although good for ballpark numbers, the materials extracted directly from a model are not precise enough to calculate the embodied carbon. Things such as waste, replacement, or incorrect extraction. You can also specify added factors, waste, and replacement factors. Carbo Life Calc will then calculate a “Total Volume”. This is the volume the program will take into the rest of the calculation.

Total Volume = Volume × Correction Formula × Waste factor × Replacement Factor

Total Volume: Total Volume in m2
Volume: Extracted or manually given volume of a material
Correction formula is a simple written text such as:
+0.5 : adds .5 m³ to the Volume
*2 : Multiplies the volume by 2
/3 : Divides the volume by 3
Waste Factor: Percentage of waste added to the material
Replacement Factor: If a material or element needs to be replaced during the full lifespan of a project this will need to be added to the materials

The weight can now be calculated by:
Mass = Total Volume × Density
Mass : Mass in kg
Total Volume: Total Volume in m2
Density: Density in kg/m³

Below are a few examples of how the volume is translated to a total volume in Carbo Life Calculator.

5.2 Definition of the embodied carbon intensities.

To get to the carbon intensity we would need to look into the material properties in detail. Various stages of a material contribute to embodied carbon. Factors such as Production, transport and construction, but also the deconstruction of elements. In the material properties you can find all these factors listed, and you can edit these based on information available from data tables and EPDs.

Total kgCO2kg = A1-A3 + A4 + A5 + [B1-B7] + [C1-C4] + D + Additional×[B4]

Total kgCO2/kg : The Embodied Carbon Intensity (ECI)

[A1-A3] : Production
[A4] : Transport
[A5] : Construction
[B1-B7] (excluding [B4]) : Life
[C1-C4] : End of Life
[D]: Out of Scope
Sequestration: Separate Value.
Additional: Added value by user.

In the above, you can see the embodied carbon of a single material calculated. This value we call the Embodied Carbon Intensity or ECI. This value is then used to calculate the embodied carbon of a carbon group.

5.3 Definition of the embodied carbon by combining 1 & 2

Once we have established the Material Mass in step 1 and the Embodied Carbon Intensity in step 2 we can now define the embodied carbon of the material group. Embodied Carbon=Mass ×(ECI+Additional)
Embodied Carbon in kgCO2e
Mass in kg
ECI in kgCO2/kg
Additional: A added value by the user specifically for this group. This can be an additional for reinforcement in concrete or nails in a timber stud wall.

The resulting value equals the embodied carbon of the material group. All the material groups will be added up to provide a material embodied carbon value.

Total material based embodied carbon = SUM(Embodied Carbon Groups)

The total material based embodied carbon is now calculated.

5.4 Getting the total value for a project

Although the materials-based value gives a good scale of the project’s embodied carbon, there is more to consider. Things like construction costs or demolition values are hard to calculate by material. Therefore, these are calculated as a global value separately, and then added to the total.

A5 (Construction) is calculated by assuming 1kgCO2 per 1400£ or dollars. These are rough ballpark numbers assumed by the RICS guidelines.
C1 is assumed to be 3.4kgCO2/m2 . These can be added in the project properties, and then added to the total.

The total embodied carbon of the entire project can now be calculated:
Total Embodied Carbon = [Total Material Based] + [A5 Global] + [C1 Global]
This defines the total embodied carbon of the entire project.

5.5 Understanding the results

The total embodied carbon is presented is total, but also as:
“x average car emission” “x nr of trees to be planted”
These values are based on average car emissions in the UK and the average carbon sequestering of a spruce or fir tree.
The SCC is also provided and an estimate of death caused due to carbon emissions.

For car emission we use 1.40 tCO2/year/car based on 9000 miles per year.
https://www.carbonindependent.org/17.html

Spruce or fir trees sequester about 180 tCO2/ha. in 30 years, per hectare of land. On one acre approx. 4440 trees can grow spaced 1.5m centres. So 0.05 tCO2/tree/30 years.
https://woodlandcarboncode.org.uk/news/carbon-lookup-tables-updated

The Social Carbon Cost (SCC) is the financial damage that the emissions will cause in the far future due to climate change, it’s a way of expressing in money what a certain emission will cost the population. This is currently set around 150 pounds/$ or dollars per ton of CO2. Although this value is expected to rise quickly the coming years, please check your local values when calculating this.
https://www.carbonbrief.org/qa-social-cost-carbon

According to studies, each 4.434 tCO2e spent now causes at least one death between now and 2100, due to air pollution and when rising temperatures make parts of the world inhabitable. This value most likely will decrease (more death per tCo2) Big emissions will have big consequences, therefor this value is now provided instantly to make emissions more tangible.
https://www.nature.com/articles/s41467-021-24487-w