Embodied Carbon Tracking Protocols

We set our LCA boundaries and tracking based on CLF's 2017 Embodied Carbon Benchmark Study, because we wanted to be able to compare our results against the baseline. The parameters we've been using since about 2019: Building life: 60 years Modules: (these are the Tally default for Whole Building report) [A1-A3] Product [A4] Transportation [B2-B5] Maintenance and Replacement [C2-C4] End of Life [D] Module D Biogenic carbon: excluded (I'd have to go back and check. We may have excluded based on recommendations from folks like Stacy Smedley rather than what CLF used for the baseline study. I don't remember. Regardless, we've been excluding biogenic carbon.) Scope: Structure, enclosure, interiors CLF has undertaken a second baseline study. They've published their data collection guidelines and a preliminary California Carbon Report: https://carbonleadershipforum.org/clf-wblca-v2/ In the new data guidelines, they are requesting that Tally users include biogenic carbon. So we'll be updating our practice to align with that. Kristian Kicinski AIA, LFA, LEED AP BD+C (he, him) Associate Principal / Director of Sustainability direct: 206.536.1370 Send me files

Tyler, we came to the same conclusions and approach that you have, focusing on the impact of the materials we're specifying for projects today (A1-A3)--not even 30-year impact but year 1 impact. Like you, GWP per square foot is the primary metric (we actually use lbs/sf rather than kg/sf because psf is easier to visualize and it seems wrong to mix SI and IP in a metric).

Modules: Maybe the underlying premise of Life Cycle Analysis (LCA)--that we know the environmental impact of how things will be manufactured in 20, 40, 60 years--is just plain wrong. All our work in advocacy has the goal that concrete, steel, glass, even paint, will be produced very differently in 5, 10, 20 years. EPIC is interesting because it bakes in (NREL) projections about how the grid is decarbonizing to look at operational carbon, but our understanding of how they will be manufacturing gypsum wall board for a renovation 30 years from now is probably very speculative.  And it seems crazy to spend time calculating the impact of taking down a building in 2084 or beyond--it will be a very different world.

Scope: The older CLF datasets were structure-only or structure-and-envelope (the scatter among early datasets was such that the mean of the set of projects that reported structure-only was *higher* than the mean of the set of projects reporting both structure and envelope!).   We're tracking Structure, Envelope, Interiors, and (lately) MEP (though the MEP inputs are a lot more spotty); this means we have to filter things to compare apples-to-apples.  Biogenic: We agree that the math on this is all a bit dicey.

• Landscape: If the carbon sequestration of the landscape around your project is significant compared to that of your buildings, you're probably not building densely enough. 
• Wood: Lots of people devoting lots of thought to this question, but it seems that if your project is building with wood that would otherwise rot (e.g., trees at the end of typical life, or insect-killed trees), then the act of building with wood can be carbon-sequestering; you're removing this potential source of future CO2 and methane emissions out of the forest and putting it in a building where you can keep an eye on it. But if trees are harvested mid-life and then re-planted--even in an FSC forest--it seems wrong to count the carbon sequestered in that wood as a credit in year 1.  Presumably, it should be a race between the carbon that the existing tree would have sequestered (in wood and soil) if left to grow vs that sequestered by the seedling--a race that might take decades for the seedling to win.  And the ongoing research on soil carbon reminds one of Mark Twain's observation: 
  "There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact."