I would like to discuss the “coverage” of LCAs (or lack thereof) and the implications on reporting.
“Coverage” or “completeness” refers to how much of the actual building material is being captured in WLCAs at any given stage. This is particularly pertinent where there is policy (being) established to assess WLCA; and/or where someone is scrutinising that assessment and comparing to benchmarks; and/or where hard limits are being set, or have been set, for embodied carbon impacts.
State of Practice (Industry)
At the earliest design stages, you can imagine (or you probably experience) that designers are most reluctant to provide material quantities. Of course, for some building components, this is less of a hurdle (e.g. structures); but for other components, this is more challenging (e.g. the envelope, internal partitions and doors, internal finishes). And then MEP (before construction) is not only too conceptual to get quantities, but the EPDs and carbon data is sparce (granted, it is improving). Sure, some benchmark data points exist, compiled by various organisations / carbon data providers – but they’re not brilliant: they’re not sufficiently transparent for us to understand what level of coverage they give (and in fact, our experience is that they are underestimating the impact of the material that’s actually being installed when it comes to construction).
I’m afraid that experience shows that improving carbon assessment coverage/completeness can be challenging. Traditional industry scopes don’t make it clear who is quantifying much of the material; not all the data needed for an LCA needed to be quantified for other reasons like cost. And at early stages, there’s insufficient time and interest to pay for that quantification (or even working out rough allowances) to happen. Designers don’t want to be the one to provide quantities because of perceived liabilities too.
Using Cost Plans
In UK practice, there is a requirement to align with, and achieve 95% coverage of, the project cost plan. However, again, cost plans doesn’t necessarily suit the carbon assessment exercise. Many costs are estimated through benchmarks and historic data; most things don’t need to be quantified.
I’ve also seen independent assessments that explicitly say that 100% of a building component category has been assessed at Concept design stage (presumably to satisfy the “95% coverage” requirement required by local policy), but only a few placeholder materials have been input with benchmark data, aligning with the concept stage-level of detail in the cost plan. It is plainly clear (from our experience…) that significantly more material is going to be identified in detailed and technical design stages, but the early assessment (and statement of 100% coverage) gives many people (clients, designers, other consultants, local authorities) a sense that the impact is going to be really low compared with regional benchmarks, without those clients & designers having to do anything particularly different.
In other words, I’m not sure there’s enough discussion about the reality that early WLCAs probably haven’t / aren’t actually capturing a lot of important material, and building carbon footprints should really be higher.
As LCA practice improves and more data becomes available, we see carbon assessment results are trending higher because more is being properly accounted for. This will be true for those who are most rigorous and thorough in assessment; not necessarily true for those aiming to capture the big elements they recognise, and who gloss over the many smaller pieces, or don’t realise what they’re missing.
Clients and designers loathe a carbon assessor surprising them with a higher impact than they expected, e.g. because their previous project assessed lower. It’s a thankless job, being a thorough assessor, capturing as much material as possible; and I suspect there are plenty of people happy to do a quick assessment reflecting concept-stage Level of Detail and spit out a small number, for less fee.
“Completeness”/“Coverage” is not a popular enough topic / high enough on the agenda to have a conversation with clients and designers yet; hence this thread.
Concluding my conversation starter
I could carry this on for a while – for example, I could talk about the different targets being set by different regions, and how low targets raise the question of the thoroughness of the data informing them; or how achieving those targets will be more challenging if “completeness” improves… But let’s not talk about the wider implications for now…
Thoughts? What are others finding?