WBLCA vs Structure Enclosure Interior LCA

Almost all of the data on WBLCA results appears to focus on three building systems, Structure, Enclosure and Interiors. This is probably missing about 35% of the upfront embodied carbon. The 9-11% of global emissions normally attributed to embodied carbon in construction was (I think) originally derived by Architecture 2030, and I have never found an explanation of the derivation. If the 9-11% was derived from historic data on LCAs based on Structure, Enclosure and Interiors, and for upfront only, is this number real? A recent article by Architecture 2030 said that if infrastructure embodied carbon was included, the share of global emissions would be closer to 15%.

Instead of beating this percentage game to death (like I am doing right now), I think one approach would be to set targets like RIBA and SBTI have done and start reducing embodied carbon using a reduced scope of Structure, Enclosure, and Interiors. Otherwise, it will be a long time before we have full scope WBLCA targets, and then practitioners need to catch up with their full scope WBLCAs.

Do I sound frustrated? I am. The design community needs to shake this ghost of perfection, and take action now. I sometimes wonder if architects and engineers think if the target is not perfect, then it is not real - therefore we can wait a little longer.

Another approach that brings the other building systems back into the picture is to set reduction targets for each building system that add up to 50-65% reductions from a 2020 baseline.

This is a big problem, and the work being done by CLF and others is amazing, and yet we are only moving the needle slowly. The King/Magwood camp probably has the best solutions for our current predicament, but try to convince architects and clients to build that way!

I apologize for the rant, and I for one will continue to spend my time and efforts to find better and faster ways to reduce embodied carbon in construction.

Bob Redwine
Advisor, Colorado Embodied Carbon Collaborative

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Hi Bob, the discrepancies between the numbers come from the fact that we are rapidly moving forward with imperfect data. We talk a lot about this in our series, “The Path to Zero Carbon”, but the industry as a whole is rapidly working to target reductions at the same time we’re just starting to identify targets, so if you see a % reduction number right now, it’s almost certainly wrong unless the scope is very clearly defined. The way I’ve found to not get hung up on these numbers is to focus more on the actual emissions - Our true target is zero, so instead of saying it’s a percent reduction, I try to get teams to focus on how close they can get to that number with the information we have (and even this comes with large caveats)

As for the Architecture 2030 numbers - as noted on their webpage, they use data sources from IEA and Statista which are looking at global material flows, not building level LCA. With any global data, there’s a lot of fuzziness to the numbers, depending on the data quality and how it is bucketed. The fact is less that buildings are exactly 15% and more that buildings and infrastructure represent a substantial portion of the global emissions, and therefore represent a large target for reduction.

Hope that helps with some of the number frustration.


Thanks Justin.

It appears that we have come to the same conclusion – forge ahead with reductions (zero by 2050?). I do think we need to set target reductions for 2030, and that is our main push now. The 9-11…15% is, however, a big selling point to those designers and owners straddling the fence on taking action. What are your thoughts on breaking out the targets by building system, so each team member would understand their part in the reductions? We are pursuing this pathway now.


the scale of the numbers is too large to directly compare the building effects and the global effects. There’s too much variability in building types, construction types, material sourcing, etc to make any sense of breaking down the global industry numbers into individual buckets. We use the 15% as a way of explaining the overall scale of the industry on climate change. On a micro level, we do LCAs covering whatever scope we can get for a project, but if we don’t have numbers for different areas (say MEP, or more in-depth interiors scopes), we can give a rough estimate. A lot of these are still unknown as we collect data, but we can at least give it a number to show that we need to reduce as much as possible everywhere, especially where we can quantify the number. And when we do have data, a large number should still be a target, regardless of the percent of the pie.

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If I had a dollar for every time I see “40%” of US energy is attributable to X, I’d be able to quit my job and search for the origin of that stat. In the end, I resign myself like Justin states to not get bogged down by numbers lacking citations, which may have been around so long as to no longer be valid anyway.

If I’ve learned anything in the past 15 yrs, it’s that zero isn’t zero. Perhaps if you include everything in BS EN 15643: 2021, but even then so much of my grid vs the grid where products are made isn’t zero, so as others have stated: “no one is zero until everyone is zero”.

My advice, layout everything in EN 15643 in front of you and make all the biggest reductions you can. Don’t be siloed unless you’ve already assessed the things outside your purview.


Certainly late to this conversation but we sometimes provide targets for disciplines, particularly when doing adaptive reuse. We also know that the massing (mostly driven by the architects) determines much of the structural emissions, so providing separate targets is only helpful to a certain extent