End-of-Life Modeling and Data in North American Whole Building Life Cycle Assessment Tools

This document summarizes the Carbon Leadership Forum (CLF) research on end-of-life (EOL) modeling for a selection of building
materials in whole building life cycle assessment (WBLCA) tools conducted as part of a larger project in collaboration with the
National Renewable Energy Lab (NREL), Building Transparency (BT), and Skidmore, Owings & Merrill (SOM.) The overarching
project goals are:

1. Improve EOL modeling in WBLCA tools by exploring data gaps and current tool capabilities.
2. Explore opportunities for developing and testing an open-access EOL database. This can potentially enable WBLCA tools
to draw from this database and better harmonize the modeling of EOL impacts.

The recommendations, limitations, and future research ideas are based on: 1) a review of EOL data and modeling functions for
three North American WBLCA tools, 2) direct interviews with North American WBLCA tool providers, and 3) a survey and an online
workshop with experienced WBLCA tool users.

The key recommendations related to data and tools are elaborated upon and include the following:
• Develop an open-access EOL database of LCA models (i.e., life cycle inventory (LCI) data and emission factors for the North
American geography). Note all three tool developers expressed interest in aligning with and/or using such a resource.
• Develop regional default EOL management rates for North America.
• In WBLCA tools:

◦ Acknowledge future uncertainties in EOL practices.
◦ Continue and/or enhance transparent methodology documentation.
◦ Enhance customization, scenario comparisons, and reporting to aid interpretation and design.

• In Stage C EOL models, prioritize filling data gaps (e.g., C1: demolition/deconstruction, C2/C3: reuse transport and
processing for all materials).
The high-priority EOL functions that LCA tool users requested are listed below. The workshop helped identify data needs as well as
potential available data to support these functions.

1. Scenario-based EOL modeling (i.e., best case, worst case, and business-as-usual scenarios)
2. Ability to customize EOL management rates
3. Choice of default EOL management rates by region
4. Customization of Module D modeling (include or exclude, change parameters, etc.)
The limitations of this study are also acknowledged and summarized below:
• The scope of this research is limited to only eight categories of construction materials.
• Findings and recommendations are primarily based on input from building LCA practitioners and WBLCA tool providers,
with limited review of academic literature.
• The survey results and workshop participation were limited in size and may not accurately depict the opinion of the North
American building LCA practitioners.
• WBLCA tool review in this research is limited to three major providers.

Finally, future research highlighted through this work includes the following:
• Expand the review of published literature and existing public and private LCI databases to identify data gaps related to EOL
modeling.
• Prioritize data gaps by investigating the relative contribution of individual C Module impacts at a building scale using a
large sample of WBLCA data and material quantities.
• Conduct further research on harmonizing Module D accounting across WBLCA tools.
• Carry out further comparisons and recommendations on biogenic carbon accounting at the end of life.
• Develop material service life defaults for North American materials.