Calculations

EMBODIED CARBON

Calculation Scope

Calculations for the embodied carbon of buildings, materials, or products, should be completed using an approved LCA tool [See Approved Tools].

Calculation scopes reference the life cycle stages as defined by standard EN 159781 , shown in Figure 1. Project teams should utilize an approved LCA tool to calculate the aggregated carbon emissions impacts of the project materials for stages A1-A5.

Figure 1. Life Cycle Assessment Scope Diagram

CARBON OFFSETS

Carbon offsets must be purchased to account for impacts of the materials and construction of the project; this includes the Product (A1-A3) and Construction Stages (A4-A5).

Aggregated totals for these stages must be data extracted from an approved LCA tool.

Embodied Carbon Accounting

The embodied carbon of the project should include the emissions associated with the materials and construction of the project scope and must not exceed the threshold of 500kg CO2e/m2 ; this includes the Product (A1-A3) and Construction Stages (A4-A5).

Aggregated totals for these stages must be data extracted from an approved LCA tool.

Reductions - Interior Materials

Interior materials that have lower than industry baseline must be selected where embodied carbon data is readily available for a product category. There are two pathways in which a product category can meet this requirement:

1. All products used in the project fall below the industry baseline. For example, all carpet tile types have an embodied carbon value of 15kg CO2e/m2 where the industry baseline is 20kg CO2e/m2 .
2. All products within the same category have a weighted average that falls below the industry baseline. For example, one type of carpet tile has a value of 25kg CO2e/m2 that accounts for 10% of the project carpeted area. The other carpet type, representing 90% of the area, has an embodied carbon value of 18kg CO2e/m2 . This results in a weighted average of 18.7kg CO2e/m2 and thus meets the requirement of falling below the example industry baseline of 20kg CO2e/m2 .

Reductions – Primary Materials

Embodied carbon reductions made in primary materials must be documented compared to a baseline that is identical to the final design except for the changes made to achieve the reduction.

Each reduction must highlight a change in the total value of embodied carbon in the project, measured in carbon dioxide equivalent (CO2e) and exported from the approved tool the team elects to use.

For example, the baseline building design may include:

• Structural steel: 340 metric tons CO2e,
• Concrete foundation: 270 metric tons CO2e, and
• Enclosure materials: 150 metric tons CO2e

This would result in a total embodied carbon value of 760 metric tons CO2e. After implementing low carbon strategies, the new design includes:

• Structural steel manufactured using renewable energy: 310 metric tons CO2e,
• Concrete mix that uses less cement per unit volume: 230 metric tons CO2e, and
• Enclosure materials with portions sourced locally: 120 metric tons CO2e

This would result in a total embodied carbon value of 660 metric tons CO2e and a subsequent reduction of 13% from the baseline building design.

The total embodied carbon value out of this assessment (660 metric tons CO2e) is then the amount that needs to be offset by purchasing carbon offsets.

APPROVED TOOLS

Tools utilized for LCA calculations must have the capability to complete a full cradle-to-grave analysis as defined by ISO 14044. In order to increase industry understanding of the LCA process and facilitate more accurate evaluations, tools that reveal their methodology and encourage data transparency are preferred.

The Institute has approved the following tools for use by project teams to conduct LCA calculations for buildings, materials, and products:

• Athena Impact Estimator - A tool that is a more sophisticated version of the Athena EcoCalculator wherein users create their own assemblies and envelope configurations, allowing flexibility for complex designs and existing buildings
• Environment Agency’s Carbon Calculator - Free downloadable spreadsheet tool that requires detailed material information such as weight of material, distance traveled and type of transportation
• eTool - Free web-based calculator with a user-friendly interface that can either use predefined assemblies or allow the user to create their own; based upon Australian product data
• One Click LCA - A web-based LCA software that calculates a variety of design data in one platform
• Tally - An LCA application for Autodesk® Revit® that calculates the environmental impacts of building materials and compares options directly within a Revit® model

The Institute has identified the following tools for use by project teams to establish product baselines:

• Embodied Carbon in Construction Calculator (EC3) - An open-source EPD database and building planner tool that enables a performance-based approach to evaluating embodied carbon reductions in design, procurement, and construction

Project teams may use a tool that is not listed if it approved through the Dialogue and is comparable to at least one of the listed calculators.

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