RMI collaborated with Alcoa Corporation, Oldcastle BuildingEnvelope (OBE), Arup, and BXP to pilot aluminum product-level greenhouse gas (GHG) data reporting following RMI's Aluminum GHG Emissions Reporting Guidance (hereafter "Aluminum Guidance”).

The pilot calculated and transferred product-level data for a unitized curtain wall used in a hypothetical high-rise residential building project in the United States, aiming to inform low-carbon procurement decisions for building projects. The pilot delivered valuable learning opportunities for all participants, improved the Aluminum Guidance, and demonstrated effective use of additional metrics, complementing typical Environmental Product Declaration (EPD) for products like curtain walls that include multiple materials.

Aluminum panels and profiles contribute an estimated 9% of the total carbon footprint of buildings. With 25% of the aluminum produced globally each year used by the buildings sector, this represents a considerable source of potential demand for low carbon aluminum. However, the building materials supply chain is often fragmented, making it challenging for architects, engineers, and property developers to access the embodied carbon emissions data of building materials. This lack of transparency into emissions data creates challenges in sourcing low-carbon materials for building construction.

The construction supply chain is complex and fragmented. Downstream stakeholders are very separated from materials suppliers, resulting in limited visibility into upstream emissions. To break down these silos and improve communication, this pilot convened key stakeholders in the construction supply chain to collaborate on improving supply chain visibility.

Typically, the demand for low-carbon buildings is driven by investors, clients of property developers like BXP, government regulations as well as voluntary commitments of property developers. BXP relies on engineering and consulting firms like Arup to perform lifecycle assessments (LCA) of buildings and inform the procurement of low-carbon materials. In many cases, the engineering firms are responsible for recommending feasible carbon emissions reductions in each material category and for writing specifications for embodied carbon emissions of various building materials. The pilot, focusing on a unitized curtain wall with multiple materials (aluminum, glass, etc.), tested the process of evaluating suppliers beyond total embodied carbon emissions, emphasizing the need to understand separate embodied carbon emissions for each material in the curtain wall system in driving upstream decarbonization.

To access this level of transparency, Alcoa and OBE reported in alignment with RMI’s Aluminum Guidance for the aluminum billet and frame components of the curtain wall, respectively. Inclusion of stakeholders along the entire value chain – from the primary aluminum producer to the property developer – was imperative to access the necessary data and provide true transparency into emission sources.

In addition to the Aluminum Guidance, Alcoa and OBE used an RMI-developed Excel tool to calculate the metrics for the benchmarking and full boundaries. This modular tool included calculation sheets for different parts of the aluminum production process; Alcoa calculated the benchmarking metrics for the billet, and OBE calculated the full boundary metrics for the extrusion profile used in the curtain wall. The metrics calculated by Alcoa using the tool aligned closely with the values in their published EPD reports. Simple tools like this can be particularly useful for aluminum companies with limited resources for product-level emissions reporting.

The engineering firm, Arup, estimated how the embodied carbon emissions of the curtain wall affect the overall embodied carbon footprint of a high-rise residential building. In a baseline scenario using a typical curtain wall, the curtain wall can contribute 12% of the overall embodied carbon of the building. In the hypothetical alternative scenario where emissions information from this pilot was used, the overall embodied carbon of the building decreases by 3% compared to the baseline scenario. However, the GHG accounting method used in the pilot might not always lead to lower embodied carbon emissions for a building. The difference between the results using the baseline vs. alternative scenario will vary on a case-by-case basis.

Standardized reporting (e.g., reporting curtain wall frame in kg CO₂e/linear-m together with the RMI recommended metrics) helps engineering firms improve modeling processes by ensuring consistency in accounting methodologies. It also improves accuracy for whole building LCAs and assists design teams in understanding the trade-offs between material embodied carbon emissions and building operational emissions in more complex scenarios.

RMI's Aluminum Guidance solves some of the barriers to the procurement of low-carbon aluminum in the buildings sector. However, certain challenges remain:

1. Despite the inclusion of material embodied carbon emissions and recycling metrics in voluntary green building certification programs (like LEED) and governmental green building policies, these incentives are not enough to drive impactful decarbonization upstream. Additional metrics should be encouraged (e.g., supplier-specific data, post-consumer scrap) to drive the use of low-carbon building materials that are produced in line with sectoral decarbonization pathways.
2. Although efforts are underway to digitize EPDs, more work needs to be done to standardize emissions data transfer along the building materials supply chain and between the various tools used by stakeholders.
3. Cost and timely delivery to the construction site remain as key challenges faced by the property developer using low-carbon materials. Certainty on scheduling and early understanding of cost impacts can assist in overcoming these barriers.

• Believes that Aluminum Guidance metrics (e.g., post-consumer scrap share, mine-to-smelter emission intensity) will help customers to better understand the drivers behind variation in aluminum product emission intensities. This growing awareness will facilitate positive long term procurement behavior among aluminum buyers.
• Expects that the Aluminum Guidance will promote discussion on efficient data transfer between tools and across value chain partners and deliver improvements to the time-consuming process of transferring and utilizing data from PDFs.

• Acknowledges the significance of the metrics outlined in the Aluminum Guidance but highlights that not all OBE suppliers are currently able to provide the detailed data required. This could be mitigated through a phased approach, implementing a few key metrics in the short-term and full metrics in the long-term.
• Emphasizes the critical role of standardized data formats, particularly for extensive data transfer between suppliers and buyers.

• Believes that the specification document provides a consistent method for measuring carbon reduction goals in carbon-intensive manufacturing processes and adds value to their construction documents.
• Highlights the need to develop more calculation tools that will help small suppliers calculate and share emissions data.

• Believes the specification document template is useful and expresses intent to recommend the inclusion of language regarding the façade system to their in-house development teams. This will enable better aluminum product-level GHG data reporting, where feasible.
• Agrees that the Aluminum Guidance and the specification document can play a role in accurately quantifying the embodied carbon for the procured material, thereby advancing data transparency related to product declarations.