Halving our emissions through low-carbon products

Author: Will Arnold, Patrick Hayes

Date published

13 July 2023

The Institution of Structural Engineers The Institution of Structural Engineers
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Halving our emissions through low-carbon products

Guidance

Author

Will Arnold, Patrick Hayes

Date published

13 July 2023

Author

Will Arnold, Patrick Hayes

The Head of Climate Action and Technical Director at the Institution present suggestions for carbon reduction in construction products.

The challenge

The message from IPCC has been clear for some time now: the world needs to halve its emissions by 2030 (compared to 2018 levels) if we are to retain any chance of keeping global warming to less than 1.5°C.

But whilst suppliers all over the world are now racing to get new materials to market that offer lower carbon versions of our standard material palette, it is a recognised fact that taking a new material from laboratory to mainstream use can take more than a decade. With 2030 now only six and a half years away, we cannot wait for wonder-materials to save us, and so we must work out how to use our current materials more effectively.

The UK construction industry is embracing the challenge, using the materials and tools we already have at our disposal. Firms are championing the reuse of existing buildings, designing with reclaimed structural components, and switching material altogether where required. And we are seeing more prioritisation of shorter spans, reduced transfers, and avoiding basements.
 

Structure containing many metal beams

What should the beam of tomorrow look like? [image courtesy of SteelCon]
 
Structure containing many metal beams

Elemental options

But once the building’s footprint, scale and concept are all fixed, the structural engineer busies themselves arranging columns, beams, slabs and walls in an arrangement that ultimately must provide a space for people to occupy.

We argue that these elements (still using the materials we already have available) aren’t yet being maximised to their full potential. How many of the beams in your building are as light as they could possibly be?

In the UK, we have a history of using material efficiently. During the mid-20th Century, construction labour was relatively cheap compared to the price of materials. As such, our designs took more human power to build, but used elements that contained far less material. Many of the riveted trusses, wrought iron arches and brutalist concrete waffle slabs of the era are still there today – proving how well efficiency and resilience can go together.

In the meantime, labour costs have increased, material costs have decreased, and we have moved away from elegant elements. We now seem to spend our days looking at the same shaped beams, slabs and walls on every construction site.
 

Two images both of train station roofs, one made of concrete, the other is steel and glass

Differing material weights at different train stations
 
Two images both of train station roofs, one made of concrete, the other is steel and glass

Back to the future

What the waffle-to-flat-slab evolution demonstrates is how easily our industry can completely change technology when the drivers dictate. In the last 50 years we’ve moved from worrying about material costs to worrying about labour costs, evolving our vernacular as a result. As we now worry about climate and biodiversity breakdown, we must evolve again.

We’re not calling for a complete resurrection of built-up beams and hollow clay pot floors. These solutions may not make sense when applied to modern-day cost plans, safety requirements and supply chain complexities. But how often are we given the opportunity to champion something other than “the same structural system as we used last time”?

The same passing of time that has changed our industry’s economic model has also seen us change the way we design and construct. Parametric tools, automated sizing scripts, robotic construction… these all give opportunities for something new and even more exciting.
 

Man stop atop a concrete vaulted thin shell slab

The Acorn thin shell vaulted slab reduces the amount of concrete by more than half, compared to a typical flat slab
Man stop atop a concrete vaulted thin shell slab


Targeted reductions

The good news is that we don’t need to reinvent the entire library of structural elements. Most of the carbon in the structure of a typical building is in the floors (i.e. the beams and the slabs). And so it is here that the innovation challenge lies. There is huge potential for manufacturers and suppliers to innovate to move us away from the modern day “norm” of steel I-beams, regular concrete beams, and the ubiquitous concrete flat slab. These are ineffective use of material, prevalent on every project. There must be a better way.

Historically we had very lean build solutions, but these have fallen out of favour for mass produced (but less efficient) solutions. Modern technologies, advances in structural understanding, and a shift towards carbon-based economics, all presents a business opportunity to innovate across all sectors.

Ever since we published our proposal for a Structural Carbon Rating System in 2020, we’ve been calling for building structures (including their floors, columns, foundations, etc.) that can be constructed for less than 150 kgCO2e/m2. That’s half of ‘business as usual’ – the challenge that the IPCC has set us.

If the floor structure makes up half of that, then we have a target of 75 kgCO2e/m2 for our beams and slabs combined.

Any engineer achieving this figure today should be proud - this is what the future looks like.

Tags

Guidance Sustainability & Environment Climate change Beam Floor Joist IStructE London HQ Carbon

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