How to assess the embodied carbon of reused building components, adaptable buildings, flexibility in design, design for disassembly, etc. ?
EC should be allocated on a project-by-project basis (treating the reuse or reclaiming of the materials as separate from the original construction project) in order to highlight the benefits of retrofit and reuse projects. However flexible a building may be for reuse, there is still the upfront carbon cost that should be accounted for, especially if the end-of-life treatment is still unknown - what if the building gets demolished anyway? I know Larry Strain has studied and written about retrofit and material reuse, mostly focused on improving existing buildings. Here’s his paper:
In my opinion, reused components should be counted as credit for avoiding the production of new components. I agree with @martintorres that it is hard to know what happens at the end-of-life of a building even if it is designed for adaptation or disassembly. That said, there should be some other way of giving credit for design for adaptation and disassembly but should be reported separately (module D according to EN 15978 standard) or accounted for using other non-LCA methods.
Here are some additional resources (unfortunately some behind a pay-wall, but if interested, reach out to the authors):
Work by National Trust for Historic Preservation:
My own paper on adaptive reuse LCA with a case study (there are many other papers on this topic):
Conference paper on evaluating flexibility and adaptability of buildings:
Catherine, from your list I would suggest that reused building components are by far the easiest to quantify on a generic basis, as in when you don’t know the specifics of the situation (I agree with Martin that it needs to be looked at on a project-by-project basis). I think that flexibility, adaptability and D4D shouldn’t get any EC credits until something is actually reused, which is the whole point. If nothing changes and the building is eventually knocked down, there is no benefit. It’s similar to the difference between “recycled” and “recyclable”, "composted’ and “compostable” etc. There are other things at play that makes it actually happen, and those are pretty important.
That’s not to say that these approaches don’t matter. It’s just that EC may not be the right metric by which to measure them. Too many what-ifs, Sounds like a great area to study for a Masters or PhD candidate!
A couple of resources to share that are background to what you’re talking about, but won’t help you with the EC question. Forgive me if you’ve already seen them.
Ellen MacArthur Foundation & ARUP Partners - First Steps Toward a Circular Building Environment - The second phase of this report is coming out next week, I believe!
A research poster I completed on Carbon Reduction Potential of Material Reuse - http://carbonleadershipforum.org/download/4198
I was US rep to ISO committee for “ISO 20887 design for disassembly and adaptability standard”. Also author of “Design for disassembly: aguide to closed-loop building”, done for King County. There is alot of guidance in both documents. There have in fact been many PhDs etc. on DfD including using LCA for the measurement. As far as metrics yes that is the most difficult part. Embodied carbon is clearly a baseline metric and Module D has been used in relation to DfD. The steel industry has refined the concepts of Module D to a fine art and it is good example of how to play this out in other materials or more generally. Their application of Module D concepts also points out the critical need for the “infrastructure” of design for future reuse. From this perspective, the first and easiest metric for DfD is to actually use reclaimed materials as long as this “new” use has not compromised the material for future reuses. Design to reuse, meaning use of reclaimed, is creating the future infrastructure to reclaim anything “designed for future reuse”, and then one can consider the embodied savings now. Unfortunately this brings up the allocation problem which is way too much to discuss in a post.
One general strategy is also making comparisons between standard practice and alternatives which in itself does not predict the future of course - however could be compared to the concept of energy modeling which is also only ever an “estimate” and seems to be accepted as a valid approach. So basically if you can “model” the adaptability/disassembly to be more efficient than current practice and also that the choice of materials are safely reuseable/recyclable. Information is paramount, so while qualitative, things like a “disassembly plan” and also “Materials Passports” increase ease or likelihood of future disassembly and reuse. While variations in how much disassembly might be needed at the component level, another basic rule to me is the degree of “contamination” and toxicity of the material.
Is this reflected in embodied carbon ? not really, so one would need more than simply CO2-e for this.
Any material which currently is not viable for reuse or recycling is a contaminant rendering DfD null. Lastly, one thing I have learned is that it is not an all or nothing proposition and variable per building type, so for each project, at least for the moment, can follow basic principles and metrics, with the application specific to that project and generate a “degree” of DfD that is the best fit.