Where you have a reuse project – a project refurbishing an existing building to renew the utility of a space – how do you present your WLCA results against the common industry benchmarks and targets?
For example:
We have various London targets/benchmarks available (LETI, London planning authorities, etc.). LETI in fact states that it assumes some degree of reuse in its benchmarks; GLA doesn’t state that explicitly, so presumably that means its benchmarks are for 100% new builds.
We do an LCA for a project which is reusing extensive amounts of substructure, facade, etc. Compared with the LETI and GLA benchmarks/targets, it will be very low.
One way we can look at it is to come up with finger-in-the-air %s, to describe how much retention there is in different categories of the assessment (e.g. approximate that 75% of the structure is retained); and we reduce the relevant benchmark sub-categories by that amount (e.g. if 75% of structure is retained, the revised structure carbon budget is 25% of the new-build budget).
HOWEVER, that finger in the air exercise is incredibly crude, and probably skewed by the fact that we better understand VOLUMES being retained, vs. CARBON being retained. So I don’t like it at all.
I am preferential to not adjusting benchmarks, and simply showing project WLCA performance against the unadjusted targets/benchmarks. The positive story in this case is that you are achieving a certain amount of useful/valuable/renewed space, without building new. The downside to this strategy is that the WLCA will look brilliant / like the project is performing really well, so there is little motivation to continue to pull together and reduce carbon further.
Thoughts?