Concrete Baseline at Bid vs. Construction

In our concrete specification, we set a project carbon reduction target against the weighted average of the applicable NRMCA regional benchmarks. In order to clearly articulate the GWP baseline, we’ve found it valuable to cite the specific version of the NRMCA benchmark report (e.g., v3.2). However, it’s certainly possible that the concrete isn’t actually procured and poured until much later, at which time a new benchmark report could be issued. Is it reasonable to hold the baseline to the benchmark values at the time of bid?
This seems to have broader relevance… do we reward suppliers for improvements against a baseline established at the time of bid, or at the time of supply?


Hi Lauren, I might message you directly too (also Arup).

I think it’s sensible to communicate to contractors/ suppliers that the baseline assumption is based on a particular benchmark; that you’d expect that the latest benchmark is considered to supersede previous concrete carbon intensity assumptions, at the time of construction; but also to acknowledge that the concrete carbon intensity achieved is dependent on a number of other factors (e.g. programme, construction method, etc.) and challenge the wider team to identify opportunities to reduce even further.

I’d say it’s reasonable to hold baseline to the benchmark values at the time of bid. This would be a similar approach to say building energy codes which are constantly improving performance and there’s a lag between bid and equipment procurement. There has to be a snapshot in time on the best available data at that time which is then carried for the project.

Also, the specification can always be written to be x% below the referenced benchmark. Energy codes and specifications from clients take a similar approach and this could be used to either drive better performance or anticipate improved benchmarks in the future.


Version 2021 (v3.2) NRMCA appears to be 0-12% below the 2019 (c3) version, even though all of the weights and materials appear to be exactly the same in both reports. Anyone know why?

We almost always, over the last few years, have specified a minimum of 30% better than NRMCA regional baselines without trouble. Most contractors use the v3 (2019) version, but we are about to begin making it clear that the baseline is the v3.2 version. Is that what others are doing?

Anyone using the CLF Baselines for concrete in their Specs instead of NRMCA?


1 Like

We are using NRMCA v3.2 in our specifications. I think concrete subcontractors appreciate using an industry reference that they are familiar with - at least in the markets I primarily work in, the subcontractors likely aren’t familiar with CLF.


Our standard is to use the 2019 baselines on all projects, but explicitly, not by reference. If we have clients that have sustainable goals, we adjust the limits by percentage of baseline.