What architects want...

An architect of many years’ standing, Scott Shell moved to the philanthropic climate change organisation ClimateWorks Foundation in 2022. Here, he offers his thoughts on ‘what architects want’ from the cement and concrete sectors in 2024...

Global Cement (GC): Please could you introduce ClimateWorks to our readers?

Scott Shell (SS): ClimateWorks is a global philanthropic organisation that focuses on mitigating climate change. I am in the Industry Programme, which works to decarbonise heavy industry, including cement and concrete. ClimateWorks accepts that the world needs cement and concrete to build affordable housing and key infrastructure, but believes that we must build cleanly. This means that we dispute the familiar trope ‘cement is hard to abate.’ We know how to do it and the industry has clear roadmaps. We are at the point where we need to set policies that allow these steps to be taken.

GC: What has low-CO₂ architecture traditionally meant from your standpoint?

SS: As an architect practicing in San Francisco, I mainly designed large buildings like schools and university research laboratories to emit as little CO₂ as possible due to their energy use. In California, this often involved moving to all-electric approaches, as renewable power is abundant in the state. It shows the ways that we can reduce in-use emissions and that there is a clear line of sight for low operational carbon emissions that can be replicated globally.

What has received less attention within the architectural community is how the embodied emissions of the building - i.e. those emitted during the manufacturing of materials - can be reduced. My personal commitment to address the climate issues associated with building materials was the reason behind my move to ClimateWorks in 2022.

GC: Is it possible to track - on a macro-level - the average embodied CO₂ of buildings?

SS: While it is difficult to put a number on this metric, embodied CO₂ is starting to decline as awareness increases. There are many effective levers, including the cement industry using less clinker in cement, the concrete producer using less cement in concrete and the builder using less concrete in the building. While it is tempting to think that this trend is limited to developed markets, it is more widespread than many imagine. Leading international developers work all around the world and take their best practice with them. There is good work starting in India, Asia and South America. This includes trends like Limestone Calcined Clay Cement (LC3) spreading from the global south to the global north.

GC: What has led to falling embodied CO₂?

SS: Contractors and developers have become aware of the many different strategies that are available, with lots of low hanging fruit that can also reduce cost. When energy codes first started, it was easy to make improvements... just add some insulation. We are at the similar early days of embodied carbon where the early gains are not that difficult. In the US, the Pacific North West saw a 20% reduction in the embodied carbon of concrete over a couple of years when projects started asking for Environmental Product Declarations (EPDs) and low carbon concrete. As they say, what gets measured gets managed.

GC: Are developers being ‘good’ or just being ‘trendy’ for the sake of the bottom line?

SS: I think that the majority of big developers want to do the right thing, as many have now experienced climate impacts for themselves. Young people in particular are concerned about how this will impact their lives. At 2050, the deadline for zero emissions is not far off for them. As they enter the workforce and advance in their careers they will bring a continued focus on low CO₂ materials.

GC: What are the most rapid ways to reduce embodied CO₂ in buildings?

SS: Most discussions about low-CO₂ in buildings have so far surrounded low-CO₂ cement and concrete products... and there is good reason for this. If we get strong collaboration across the value chain, as we are seeing for many large projects, from architect to developer to concrete producer and cement producer, it is possible to change the recipe very quickly. It is not as easy to change the recipe for steel, glass, aluminium or bricks, all of which need changes to the manufacturing lines.

However, it is clear that - due to an historic focus on speed and cost - we currently use more concrete than is needed in buildings. Flat slabs in multi-story buildings are fast to form, but much of that concrete is just dead weight and not contributing to structural performance. Researchers, including at ETH Zurich, Switzerland, and the Acorn Project at the University of Aberdeen, UK, are looking to change that with ‘strength through geometry,’ essentially doing more with less. Can we develop new formwork systems and construction techniques to maintain speed of construction while reducing material use?

While a lot of this research is nascent at this point, I expect to see lots of innovation in this area. Using less materials reduces material cost, but also the weight of the structure for compounding benefits. The Global Cement & Concrete Association (GCCA) roadmap to net zero anticipates that 22% of all of the CO₂ savings will come from efficiency in design and construction.

The use of other materials, including mass timber, has also been touted as a way to reduce embodied emissions and many architects are excited by the prospect. However, most new construction will occur in the global south where the timber resources just don’t exist at the scale needed.

GC: How might artificial intelligence (AI) affect decarbonisation in costruction?

SS: I was sceptical in the past, but now be-lieve that AI will be a useful tool in concrete mix design in the future. There are researchers and mix designers than can design very low carbon mixes, but there are not enough of them for the enormous scale of the concrete industry. AI can help expand this existing expertise and speed the development of new mixes.

On this point, I recently saw a presentation from our local ready mix producer that showed how AI can be used to narrow down the range of possible mix solutions before the mortar testing stage. This could save a lot of time, money and CO₂.

GC: What about 3D printing?

SS: There is a lot of excitement about 3D printing for the ‘coolness factor,’ but we are not convinced it will have a major role in the concrete industry. There are two main reasons. Firstly, current 3D printing concrete mixes are often high-CO₂ blends with a lot of binder and less aggregate, which under-mines the benefits of using less concrete. And we need concrete for infrastructure and large residential buildings in the global south. I don’t think 3D printing is going to be a major part of the required solutions.That said, 3D printing for intricate moulds that are then used for pre-cast elements could facilitate the ‘strength through geometry’ approaches that I mentioned earlier.

GC: What role should national govern-ments play in the development of low-CO₂ approaches?

SS: ClimateWorks does a lot of policy work on low-CO₂ approaches to construction, including supporting the Inflation Reduction Act 2022 (IRA-22) in the United States. While the industry could decarbonise on it’s own over time, the speed of change required by the climate crisis demands much faster action. This requires national and sub-national governments to step up and implement policies, requirements, incentives and provide funding. Many strategies to reduce emissions are cost-effective today, including supplementary cementitious materials (SCMs) like calcined clays, aggregate gradation to reduce paste content, and better quality control to avoid over-design.

However other strategies, like CO₂ capture, utilisation and storage (CCUS) are costly. We can’t expect cement producers to commit to expensive investments and not protect them from being undersold by ‘dirty’ producers. Policies to make it fair are therefore essential.

Absorbing the costs of CCUS will be expensive at the cement plant level, but cement is not used in isolation. Good policies will allow the cost to be distributed appropriately across the whole value chain. ClimateWorks estimates that decarbonisation of cement will add only 1 - 2% extra on the cost of a new building in markets with high labour costs. This minor premium can first be absorbed through Green Public Procurement on government funded projects such as infrastructure, which can account for over 40% of cement use in many countries.

GC: Large cement and concrete producers are transforming into ‘building materials producers.’ How will their mind-sets and building practices change as they do so?

SS: Cement and concrete producers, increasingly conscious of their CO₂ footprint, are diversifying. I think they are looking for synergies among these different business lines. We have seen the adoption of waste processing activities to secure alternative fuels, and tie-ups with steel and power producers to secure supplies of SCMs, much of it to reduce cost, with a CO₂ benefit on the side. More recently, they have been buying up natural pozzolans, clay reserves and demolition firms so that they can expand into new SCMs. There will also be opportunities to use CO₂ captured from cement
production.

Finally, it is important to remember that cement and concrete are very low margin businesses with big capital investment costs. There may be an element of simply wanting to move into more lucrative, higher-margin areas, regardless of other concerns.

GC: Are contractors willing to pay extra for low-CO₂ buildings?

SS: The top of the market certainly is willing to pay extra, but we need the right policy environment to expand it much more broadly. We need policies such as green public procurement, codes and standards that mandate lower carbon materials and building designs. We need businesses, construction and engineering firms to commit to low carbon projects, such as ConcreteZero and the First Movers
Coalition.

GC: Will producers be able to produce enough low-CO₂ building materials?

SS: They can certainly produce enough material, but there has to be a viable business model with supportive policies, codes and standards. And producers can’t do it alone, we need the entire value chain engaged with engineers specifying low carbon materials, removing overly prescriptive and conservative specifications. We need contractors to step up and start leading on this issue. We need owners to demand lower carbon mixes, as part of their company wide climate commitments.

When I started practicing architecture everyone was in their own silo. However, today there is a clear trend toward collaboration across the industry, from cement producer to concrete producer, contractor, architect, engineer, concrete pumper and concrete finisher. This collaboration is essential to reach our goal and it is a lot more interesting than living in a silo!

GC: Thank you for a very interesting discussion!

SS: Thank you Peter - it was great talking with you.