Embodied energy and the proposed SCORS rating

I recently came across an exciting article, published in the December issue of the IStructE magazine, about carbon in construction and the path to net-zero buildings in 2050.

What’s interesting here (and a little revolutionary, frankly!) is that the authors have developed a scoring system for buildings based on the estimated total emissions allowed globally until 2050, in order to maintain a 50% chance of staying below 1.5C average temperature increase (which is estimated by scientists as the tipping point where a bad situation turns really, really bad). From that total value, an amount earmarked for the embodied energy of buildings is calculated based on the current distribution of emissions across industries, and that number comes to 21GtCO2eq (twenty-one gigatons of carbon dioxide equivalents). Okay, so that’s a mouthful, but what does it mean? Well it means someone has had the clever idea of making a darn plan. A plan for for how the construction industry can hope to achieve the targets set out for it in the Paris Agreement. Working backgrounds from the goal at year 2050 to the situation in 2020, what emissions are we allowed? It’s like a budget. Or a road map. And this road map is great, because where the task of stopping climate change can seem monumental, to the point of being paralyzing, it is a light at the end of the tunnel. Without measurable goals like this, based on quantitative analysis, you’re as good as working blind and it’s pretty hard to achieve anything like that. In the words of Peter Drucker, ‘What gets measured gets managed’. None of this is news, really, but it is the first time I’ve come across an actual pathway towards net-zero for construction. Of course, this isn’t the pathway itself, but rather the description of the path, but without this, we risk spending our efforts incorrectly or assuming we are closer to the goal than we are.

This is exciting for two reasons:

-It gives a REAL target value to aim for; one which is based on analysis and (hopefully) reflects a path to success, rather than the innumerable existing guidelines stating just ‘reduce carbon, it’s bad’ which is rather vague and not very actionable (the same reason scores like ‘LEED PLATINUM’ or ‘DGNB GOLD’ are hard to understand in context of the greater goal). This target value is non-static reflecting how we should be getting better and better at reducing carbon in construction every year (are we?).

-With real targets and a scoring system to evaluate performance against, we can literally ask whether a given project is bringing us closer to or farther away from the goal of halting the worst effects of climate change. We could also market ourselves on good performances, with a legitimate absolute comparison to target values, rather than relative comparisons to ideal projects or pilot projects deemed to be winners (which always beg the questions by who and how).

But it’s also pretty sobering….

-The industry average based on the sample projects used was measly E-rating (250-300kgCO2/m2)

-In order to stay on track, we would need to achieve an average of an A-rating by 2030 (100-150kgCO2/m2)

Note that all of this is based solely on embodied carbon i.e. the carbon in the construction materials, and does not include non-structural components or the operation of the buildings. As, a structural engineer, this is however, the part the excites me the most, and I think it is also the part that has been missing for the longest time. It is far easier to swap between facade elements, ceiling panels, even floor build-ups in order to compare the CO2 results and upgrade your design. It is far more difficult to keep the design concept intact and totally replace the structural system, or to address the inefficiencies in a given structure without influencing the building design (not that we shouldn’t do this! I am trying to emphasize the difference in difficulty in ‘upgrading’ a design in terms of CO2 emissions performance). The construction industry has over the past 10-20 years become increasingly good at reducing operational energy, to the point where net positive buildings are possible, and so the emphasis in effort for reducing CO2 emissions lies more and more on the embodied carbon.

However, the calculation does also reflect the distribution of emissions over the lifetime of a building, i.e. the target goals assume that embodied carbon is approximately 66% of a building’s total emissions.

Internally, we have developed simple tools to allow us to rate our concepts and options in the design phase, ensuring the overall carbon performance is a design criteria evaluated and discussed throughout design. The SCORS rating works best in helping give context to option comparisons, as well as general performance of the overall design. We are also working on calculating scores for all our past projects (real and theoretical) to form an internal database (which could also be added to the various industry databases logging such info).