EMBODIED CARBON IN GREEN RATING SYSTEMS

Section 5.1  Whole Building Life Cycle Assessment (WBLCA) (26 points)

Structural engineers play a critical role in developing and interpreting WBLCA results, particularly in evaluating embodied carbon impacts associated with structural systems and materials. In many cases, they lead early design decisions that significantly influence Global Warming Potential (GWP) outcomes. To achieve 3 points per Green Globes Section 5.1.1.1, the project team must conduct a Whole Building Life Cycle Assessment (WBLCA). The life cycle assessment must conform to ASTM E2921-22 Standard Practice for Minimum Criteria for Comparing Whole Building Life Cycle Assessments for Use with Building Codes, Standards, and Rating Systems. The life cycle assessment must minimally report the following life cycle impact indicators:

• Global warming potential (GWP);
• Acidification potential; 
• Eutrophication potential; 
• Ozone depletion potential (ODP); and 
• Smog potential

Operating energy consumption and MEP systems may be included in the life cycle assessment

Section 5.1.1.2 includes up to 7 additional points for demonstrating a reduction in GWP relative to a reference building “of similar size and function” (see Table 2).

Section 5.1.1.3 included up to 16 additional points for demonstrating a reduction in at least three impact indicators (one of which must be GWP). Table 3 lists the points that would be awarded to the team based on the percentage reduction. 

For showing a reduction in GWP only:

• Compare two similar building designs.
• Demonstrate reduction in Global Warming Potential (GWP).
• Can use: Full ASTM-compliant Whole Building LCA, OR Embodied carbon calculator (GWP-only comparison).

Table 2. GBI Green Globes for New Construction 2024, Section 5.1.1.2

For showing a reduction in multiple environmental impacts:

• Compare at least two designs using full ASTM-compliant LCA.
• Must reduce impacts across at least three impact indicators (one must be GWP).
• The selected design:
  • Must match the design chosen in 5.1.1.2.
  • Cannot increase any other impact category by more than 5% vs the reference design.

Table 3. GBI Green Globes for New Construction 2024, Section 5.1.1.3

Section 5.2 – Product Life Cycle (29 points)

By asking structural material manufacturers for product-specific EPDs and LCAs, structural engineers can drive the market toward transparency regarding the environmental impacts of the materials they specify on their projects. This influence extends across Section 5.2.1, where design teams rely on product-specific environmental data to inform material selection and demonstrate compliance with life cycle–based credits.

5.2.1.1 Product Life Cycle: Cradle-to-Gate

In practice, structural materials often contribute a significant portion of product-specific EPDs submitted for this credit. For example, ready-mix concrete may have one EPD per mix design, and structural steel, reinforcing steel, and mass timber products commonly have manufacturer-specific EPDs available.

While the rating system awards points based on the total number of qualifying products, design teams should be aware that each product-specific EPD must represent a distinct product. Structural engineers can support this effort by coordinating with suppliers and incorporating EPD requirements into project specifications to increase the availability of qualifying documentation. This section of Green Globes requires the design team to provide at least 15 third-party verifications/certifications evaluating cradle-to-gate life cycle environmental impacts for the project. Depending on the number of products submitted for the project, up to 29 points can be achieved. Manufacturers must provide one or more of:

• Third-party verified Type III EPDs (ISO 21930 / ISO 14025)
• Third-party multi-attribute product certifications
• Third-party verified product LCA (ISO 14040 / 14044)

(Older ISO 21930:2007 EPDs allowed through Dec 31, 2024.)

5.2.1.2 Product Life Cycle: Cradle-to-Grave

This section of Green Globes requires the design team to provide at least 5 cradle-to-grave product-specific Environmental Product Declarations (EPDs) or product life-cycle assessments for the project. Depending on the number submitted for the project, up to 10 points can be achieved. It is a benefit not only for the project, but also for the industry since cradle-to-grave product-specific, third-party verified Type III EPDs and product LCAs produce an accurate picture of the environmental effects of a manufacturer’s product. 

Scoring Matrix

Section 5.4 – Product Sustainability Attributes (15 points)

5.4.1.1 Product Sustainability Attributes

In this section, structural engineers can help the project team achieve fifteen points and reduce the structural system’s embodied carbon by specifying materials with pre- and post-consumer recycled content, biobased content, or third-party sustainable forestry certification. The availability of recycled content varies by material due to resource availability, manufacturing processes, embodied carbon considerations, and market demand; for example, structural steel typically contains a high percentage of recycled content, whereas additional coordination may be required for cold-formed steel. For projects utilizing structural timber or other biobased materials, engineers may specify third-party sustainable forestry certification, which should be coordinated early to maintain cost effectiveness, as it can influence procurement options; however, biobased content alone may still contribute toward credit achievement where permitted.

Green Globes recognizes and accepts the Forest Stewardship Council (FSC), Sustainable Forestry Initiative (SFI), and American Tree Farm System (ATFS) sustainable forestry certifications. Research (see Note 3 under References) has shown timber harvested from responsibly managed forests can contribute to a lower embodied carbon footprint when compared to non-certified wood. Using building products with sustainable attributes can achieve up to fifteen points for the project.

Section 5.5  Reuse of Existing Structures and Materials (30  points)

5.5.1.1 Reuse of Structural Systems and Non-Structural/Interior Elements (22 points)

Reuse of existing structural materials on a project both on and off site can help reduce the demand for new materials and the structure’s carbon emissions from extraction and manufacturing. Structural engineers will need to assess and determine the condition and strength of existing structural elements to ensure they will be adequate for the demands of the proposed design. It is paramount that structural engineers are engaged during schematic design when building and material reuse is a design option.

Depending on the percentage of the existing structural system that is reused (relative to total square footage of the entire structural system on the project), up to 12 points can be obtained in Section 5.5.1.1.

Scoring Matrix

5.5.2.1 Material Reuse from Off-Site

Potentially four points can be achieved for materials on the project that are reused, refurbished, or off-site salvaged. The points for reused materials sourced from off-site are based on their value relative to total material value.

Scoring Matrix

Section 5.6 – Waste (26  points)

This section focuses on reducing waste across the construction material supply chain. Structural engineers should engage early in waste planning to help minimize material quantities, reduce generation rates, and support diversion strategies. This includes collaborating with the general contractor and material suppliers to optimize framing layouts, material selection, and overall material efficiency.

Scoring Matrix

Section 5.7 Resource Conservation (10 points)

5.7.1 Off-Site Fabrication for Construction Optimization

This section provides the option for project teams to utilize off-site fabricated building elements through modular or prefabricated construction. Structures applying modular or prefabricated construction usually benefit from shorter site phase programs, increased worker safety, and reduced material waste and transportation-related embodied carbon. The quantity of points (up to four) awarded for utilizing modular or prefabricated construction is dependent on the percentage by cost, not including site work.

5.7.2.1 Design for Deconstruction (DfD) 

Green Globe awards 6 points for documenting the application of design for deconstruction (DfD) principles in the design of the building and providing the Owner with a Deconstruction Plan that addresses both partial deconstruction (for renovations) and total deconstruction (for end-of-life removal) of the building to maximize the reuse and recycling of building components and materials. While this strategy will not usually reduce short-term embodied carbon associated with the construction of the subject building, it has the potential to reduce future GHG emissions at the building’s end-of-life when the materials are deconstructed and reused in new construction in lieu of new materials.

Structural engineers can support achievement of this credit by incorporating design strategies that enable future disassembly, reuse, and recycling of structural systems, and by providing information needed for the Deconstruction Plan. Key contributions include:

• Design reversible connections: Utilize bolted or mechanical connections where feasible in lieu of permanent welded or cast-in-place systems to enable disassembly without damage.
• Enable material separation: Configure structural systems to allow separation of primary materials (e.g., steel, concrete, timber) and avoid highly integrated or composite assemblies where reuse is intended.
• Standardize and modularize systems: Use regular grids, consistent member sizing, and prefabricated/modular components to improve reuse potential and ease of disassembly.
• Identify reusable structural elements: Highlight structural components with high reuse potential (e.g., structural steel framing, precast elements) and coordinate with the project team on salvage strategies.
• Document structural systems for deconstruction: Provide information on structural layout, connection types, and material quantities to support both partial (renovation) and total (end-of-life) deconstruction planning.

Coordinate with the project team: Work with architects, contractors, and owners to align structural design decisions with deconstruction sequencing and material recovery goals.

References (NC 24)

1. Green Building Initiative (GBI). ANSI/GBI 01-2024: Green Globes Assessment Protocol for Design, New Construction, and Major Renovations.
2. Carbon dioxide equivalent (CO₂e): A standardized metric representing the global warming potential of greenhouse gas emissions across a product’s life cycle.