Sustainability Segment | Part 1: How can you create a sustainable concrete architecture?


Are you serious about sustainability? If so, it doesn’t have to cost and arm and a leg. Before you start, think about how you can Re-use, Reduce and Recycle.


Let get started..

So you’ve pushed and pushed (as has the engineer, hopefully) to develop a low-carbon scheme, but the concrete frame industrial complex approach has won and your timber and hempcrete has been case side in its favor.

Unfortunately, this is the story of too many projects, with logistics and construction uncertainty around ‘green’ construction creating barriers that only an experiences team and an ambitious client can overcome.

So, what happens next? Too often the design spirals deeper into the mire, with climate aspirations sacrificed on the alter of economic efficiency, and we end up with uninspired designs that we’ve produced for decades, with high embodied carbon and limited innovation. But don’t lose hope, there’s plenty we can do to salvage the design and perhaps find concrete a place in the ‘green’ design.


Reuse


It is now widely accepted that re-using existing assets is the best thing a n architect or engineer can do for the planet.

So when a starting a scheme, we should look to re-use elements on site, from full retention of the existing building, re-use of the existing foundations or simply recycling materials and finishes. This is predicated on specifying suitable surveys and testing, to understand the opportunities, then working with the existing fabric, rather than against it.

Often minor tweaks to the proposals, with in footprint of sequencing, can hugely simplify the works, reducing demolition and new structure by retaining key elements. This is when good communication is critical, as each discipline brings its own knowledge, and open discussion and challenging ‘negative’ decisions are essential.

Once you’ve decided what to demolish, try to find opportunities to re-use the ‘waste’ material. While re-use isn’t carbon negative, it generates significantly less impact that using new materials. The engineer should be looking for record drawings and specifying testing early to ensure this opportunity isn’t missed.



Concrete Plinth House by DGN studio



Reduce


Once the scope is finalised, recover some of that initial lost ground through the design, with clever framing, and ensuring that the architecture responds to the structure rather than forcing the engineer to accommodate complex and inefficient demands.

At its simplest, moving from a 6m grid to an 8m grid will increase the slab thickness from around 225mm to 275-300mm, a 30% rise in concrete. Similar problems arise from set backs and transfers.

These decisions cascade down the building, with columns, beams and foundations all working harder to support an overweight slab, further raising embodied carbon and cost.

This doesn’t force us to sit in a bleak block, with a grid of columns marching into the distance. Designers should embrace the benefits of concrete; it can be cast in any shape and is great in compression. We only need to look to classical architecture to appreciate curves. The industry is obsessed with flat slabs (we are too), but this must change if we are to ‘solve’ the climate crisis.



Concrete Plinth House by DGN studio


Recycle



Finally, once design opportunities have been exhausted, we should be specifying low-carbon concrete mixes that have high proportions of cement replacement and recycled aggregates.

While a critical part of sustainable design too often this ‘green washes’ a carbon intensive design, skipping the steps above. Cement replacements (GGBC/PFA etc) aren’t truly carbon neutral, if you’re buying it, it’s not ‘waste’, but they can significantly reduce the embodied carbon of structures.

This can offer eCO2 savings of ~40% compared to ‘baseline’ concrete, but realistically the saving compared to ‘industry standard’ is probably half that.

To address the climate crisis we must embrace the opportunities of Reduce, Reuse and Recycle, brining creativity, innovation and good design to ‘green’ concrete, not jumping to the easy promise of ‘carbon-negative concrete’ (Steve Webb and Liam Bryant, Webb Yates Engineers. RIBAJ 2021, p65-66)


Concrete Plinth House by DGN studio



Concrete and sustainability are two words that are often considered incompatible. Used as early as the Roman era, concrete has shaped much of our built environment, being the most widely used manufactured material in the planet thanks to its resistance, versatility, cost-effectiveness, and accessibility, among other inherent benefits. Its popular use in buildings and infrastructure forms the foundations of cities, connects communities, and will continue to play a vital role in providing solutions to the challenges of the future – especially as cities must respond to a growing global population. But with cement as its key ingredient, it also comes with several environmental costs, being responsible for at least 8% of the world’s carbon emissions in a climate-change context. However, it doesn’t necessarily have to be that way. With the rise of innovative technologies and products, there are many ways to make concrete greener. Source: Archdaily