Frequently Asked Questions
Why use the Embodied Carbon Pathfinder?
Pathfinder is primarily an educational tool that will introduce users to life cycle assessment and will help them gain a high-level understanding of the embodied carbon implications associated with various combinations of design decisions for the archetype buildings. The tool is intended for use in early design or pre-design for general guidance, when a custom life cycle assessment (LCA) study may not yet be feasible. Pathfinder can also be helpful for projects subject to an embodied carbon policy; it can help during early design to establish some high-level decisions that may increase the chance for compliance with an embodied carbon limit.
What’s the difference between this tool and the Athena Impact Estimator?
The Impact Estimator is a whole-building LCA tool that can model any work of construction and delivers live life cycle assessment (LCA) results. The Embodied Carbon Pathfinder, on the other hand, is displaying fixed data that was pre-calculated in the Impact Estimator for specific archetype buildings. Results shown here are only roughly applicable to any building other than the ones modeled. Pathfinder does not replace tools that perform live LCA on a user’s specific project.
What’s the difference between this tool and other embodied carbon tools?
This tool is built on results from the Athena Impact Estimator for Buildings, with high-quality regionalized life cycle inventory data in the background, with the full building core and shell included in the model scope, and with the full cradle-to-grave life cycle modeled. Other tools may not be as comprehensive in scope and life cycle boundary and may be relying on less consistent or less regionally appropriate background data. On the other hand, this tool is not doing a live calculation on user-specified material types and quantities as with some other tools, which means this tool is less project-specific. There are always trade-offs between accuracy and simplicity in these kinds of tools. One feature unique to this tool is the ability to quickly modify the design variables and visualize results across multiple options.
Is this tool applicable to other geographic regions?
The archetype buildings and the LCA results are specific to the Vancouver and Toronto metro regions in Canada but are generally applicable for other areas of British Columbia and Ontario. Results may be significantly different for other regions due to different transportation grids, building code requirements and electricity grid carbon intensity. More regions and building archetypes will be added as funding allows.
How were the archetypes determined?
Building archetype designs were developed using various tactics, including review of drawings of similar buildings, stakeholder consultation, and team knowledge of the building industry in the regions. The archetypes are fictional buildings but intended as representative of the actual building market.
How were the design variables determined?
The types of variables and the available iterations within each category were determined based on construction industry practice, feasibility, stakeholder consultation, and significance for embodied carbon.
How were the results generated?
The Athena Impact Estimator for Buildings whole-building life cycle assessment (LCA) software tool was used to generate results. For each archetype, every combination of variables was modeled in the software, generating over a million sets of results. Impact Estimator results were slightly adjusted where workarounds were needed due to gaps in the background data.
What building components are included and excluded in the results?
The LCA model for each archetype includes the complete building structure above and below grade, the building envelope above and below grade, and all glazing systems. Parking garages are included. Excluded: ceiling or floor coverings, finish materials, paint, interior walls, mechanical and electrical systems, and site components. Note the gypsum board on the inside of exterior walls is included.
What life cycle stages are included?
The system boundary for the LCA models includes the product, construction, use and end of life stages excluding operational energy and water (in other words, the A1-A5, B1 to B4, and C1 to C4 life cycle stages). Users have the option to constrain the results to just A1-A5.
Is biogenic carbon included?
The results can be viewed with or without biogenic carbon.
How accurate are these results?
The data used was developed with Athena’s Impact Estimator tool, so the results are as accurate as the Impact Estimator allows and only as applied to the building archetype. The difference between an actual design and the building archetype would normally represent the largest error. However, it is important to note that there is uncertainty in all whole-building LCA results due to data gaps, methodology issues, and the inherent uncertainty because of the multiple assumptions that must be made for cradle-to-grave LCA. All whole-building LCA results should be viewed as an approximation.
How applicable are these results to a particular design project?
These results are specific to the archetypes that were modeled and therefore would represent only a rough approximation for a different building. More accurate results for a particular design project require the use of whole-building LCA software like the Impact Estimator.
What are the limitations of this tool?
This tool is not conducting live LCA – it is using pre-calculated LCA results. These results are specific to the archetypes and geographic region that were modeled and therefore would represent only an approximation for a different building or different location. More accurate results for a particular design project require the use of whole-building LCA software like the Impact Estimator.
What is GWP?
Global warming potential (GWP) is one output of life cycle assessment. The GWP result for a whole-building LCA (excluding operational energy) is often identified as “embodied carbon.” GWP is measured in mass of carbon dioxide equivalent (CO2e). It represents emissions of CO2 and other greenhouse gasses (methane, nitrous oxide and ozone) resulting from the production, transportation, and use of materials and energy through the life cycle of a building.
Why is the GWP range here different than other published ranges?
The results from different LCA studies are often not comparable, due to different scopes, system boundary, methods, assumptions, background data, tools and so forth. With so many ways that one study can differ from another, two unrelated whole-building LCAs can be an order of magnitude apart. This means that the magnitude and range of GWP values in this study are only relevant within the context of this study and are not comparable to a different study.
Why are some GWP results negative?
If including biogenic carbon, wood products have a low or even a negative GWP; the GHG removals by the living tree can outweigh the GHG emissions from manufacturing. Some of the archetypes in this study have so much wood content that the negative GWP from the wood is larger than the positive GWP from the other components. Biogenic carbon can only be included as a GWP credit (a negative) if the wood was sustainably sourced; wood in Canada and the US meets that criterion per ISO 21930. Although ISO 21930 and the National Guidelines for Whole-building LCA specify that biogenic carbon should be included, this is a controversial issue for some.
Is every possible combination of variables possible in the tool?
No. In order to limit the size of the database and make the tool faster, some combinations of variables were disallowed. Disallowed combinations were limited to unlikely or impractical combinations in real world applications. For example, it is very unlikely that a concrete floor will be supported on wood columns, so selecting this combination is not possible in the tool.
Do the archetypes include concrete podiums?
Yes, for high-rise commercial, high-rise MURB, 10 storey commercial, and mid-rise MURB. The high-rise archetypes include taller ceiling heights for the first floor, which is typical for most mixed used buildings.