When you're going somewhere new, you need a map - otherwise, chances are you'll get lost. Or so it used to be before we all carried digital maps around in our pockets. The point stands, however, that when traversing foreign territory, guides will help you get to where you want to go.

For a long time, people of the world have alerted any and all other people of the world that we need to reduce our collective carbon emissions. In the construction industry, the discussions have intensified over the past 10 years, to a point where the energy on the consultancy side has reached critical mass. Everyone is talking about sustainability (the word feels tainted now). But the fact is that we, despite the hype, have very few steps in the direction of zero-carbon construction in our rear-view mirror. We are not creating demonstrably better (i.e. lower-carbon) structures beyond pilot projects, and the few steps we have taken are swamped by the increases in construction projects undertaken, as the third world struggles forth into middle class, and the first world prefers to demolish all veteran structures in our spoiled habit of having new, always.

And changing an organism with the size and dispersion of the construction industry is not easy. We can't prototype, failure is often unacceptable, we are at the mercy of clients and their wallets, and we are quintessentially brick-and-mortar meaning we can't expect tech to come in and disrupt us to success (wait, hold that thought...). But regardless of all that, and perhaps especially because of all that, we need a better roadmap for getting us from point A to point B. A being here, now, and B being a zero-carbon future, preferably before 2050. And finally, we might be getting it.

The recently developed SCORS rating (Structural Carbon Rating Scheme) provides this roadmap. SCORS was likely inspired by the only slightly older LETI initiative and RIBA Climate Challenge, which both set benchmark values for the construction industry to strive for, and offer to different mechanisms to make it happen (stakeholder and bottom-up engagement for LETI and peer competition for RIBA). However, both the LETI and RIBA target values are somewhat arbitrary. They represent reductions from current average level, and they are ambitious, certainly, but they seem to be plucked out of thin air, i.e. their basis and rationale are indeed just that they are ambitious and we think that will necessary. This is a great start and a necessary step, but to my mind, it lacks a certain scientific rigor. In comes SCORS.

SCORS takes an upper bound approach, calculating backwards from a best estimate of the world total carbon budget allowed for in order to stay below 1.5 degrees of average warming. This total emissions pie is then sliced into smaller and smaller pieces, representing the contribution of the construction industry to global emissions, of building structures to the construction industry and of structural materials to all building materials. The result is an embodied carbon budget for structural engineers and a very clear statement - if we spend more carbon than this in the next 30 years for structural materials in ALL structures across the world, we will have failed our part in the global goal.

This is a huge step forward. I can't overemphasize how helpful this will be to myself when designing and trying to push for (ugh) sustainable designs. I hope you all do to.

‍

Okay, quickly, the numbers. The images below show an overview, although you have to remember to convert all targets to LCA stages A1-A5 (embodied carbon in materials) and then take the percentage of that which is structural materials, on average. The authors use 66% for that.

LETI

RIBA CC

SCORS

And there's a whole lot of details on the specific numbers and semantics that I didn't get into, because they muddle the message. Which LCA stages to consider, net-zero vs whole life zero, offsets; yay or nay, operational energy, circularity, end-of-life use. All these topics are important, for sure, but I want to focus exclusively on embodied carbon. We are all familiar with task of quantity calculation for price estimation. The task for carbon counting is no different. This is the realm of the structural engineer, and this is where we must shine.
‍

‍