Getting scientific with carbon

Carbon is the elephant in the room when it comes to construction and the built environment. Simply put, our industry is creating too much of it and has been for decades. When it comes to the cement industry alone, if it were a country it would be the third highest emitter of carbon behind only China and the USA, and that’s before you start adding in the carbon cost of steel.

A whopping 38% of global energy and process-related carbon emissions come from the construction industry, 11% of which came from the manufacturing of building materials. Much is riding on the industry’s ability to take responsibility and enact genuine change.

We can’t just rely on governments to regulate us out of this mess. We need to be proactive and actively look to make the changes needed to reach 2030 targets. We recently wrote about the role of engineering in the push for net zero. This time we’re going to talk about how we as engineers go about measuring embodied carbon in our designs.

Only by taking a scientific approach, where we carefully measure the carbon output of our designs, can we start to innovate and find ways to bring that figure down using smart engineering.

The lifecycle stages

Carbon is embodied in all stages of a building’s life, affected by everything from material harvesting to demolition and re-use.

Stages A1 to A5 – Material harvesting, manufacturing and building processes

The carbon here is produced by acquiring the materials needed for the building, processing them from their raw form, transporting them and installing them in the building.

  • A1 – Extraction of raw materials
  • A2 – Transport of materials to the factory
  • A3 – The Manufacture of products
  • A4 – Transport to site
  • A5 – Construction of the building

It’s during these stages that we, as engineers, can have the most impact. Where appropriate, we can design for less carbon-intensive materials or create designs that are efficient and require fewer materials.

Stage B1 to B7 – Building maintenance and use

These stages are all about the carbon utilised by the building once it’s up and running. Typically, this is the domain of MEP engineers, who’ll dictate the nature of the building’s energy source and its consumption of energy in use. It’s also during these stages that additional work can be done on the building, normally taking the form of a refurbishment or fit-out.

  • B1 – Use
  • B2 – Maintenance
  • B3 – Repair
  • B4 – Replacement
  • B5 – Refurbishment
  • B6 – Energy use
  • B7 – Water use

C1 to C4 – End of life

The end-of-life stage is simply the carbon expended in demolishing the building and processing the waste materials.

  • C1 – Demolishing the building
  • C2 – Hauling away waste materials
  • C3 – Recycling
  • C4 – Disposal

Beyond the life cycle

Once a building has reached its end of life, the recovered and recycled materials can then be reused in new schemes.

How can engineers make a difference?

For us to hit the LETI 2030 targets and global targets for 2050, every contributor to a scheme has to make efforts to adapt and change how they work. The elements that are firmly within our control as engineers are the structural and civil aspects of building design. That means the embodied carbon sequestered in lifecycle stages A1-A5 are where we make our mark.

When it comes to structural frames, floor plates and piling, you’ll see a lot of steel and concrete being used. Although these are fantastic materials in terms of their function, they’re incredibly carbon-intensive. As we’ve said elsewhere, it’s tempting to think we can simply wait for science to give us an all singing all dancing carbon-free alternative, but that’s pie-in-the-sky thinking.

By pursuing efficiency in how we use these materials we can make a difference in the here and the now. Of course, this won’t get us to net zero on its own, but we can drastically reduce our embodied carbon right now and start knocking on the door of those 2030 targets. We can’t think in a binary fashion of “it’s either no carbon or lots of carbon”, we have to start making incremental progress towards those lofty net-zero goals by being more sparing and efficient with carbon-intensive materials.

But how do we measure it?

In our last discussion piece, we covered how designing for efficiency, reducing waste and thinking carefully about material usage can help put us solidly on the path to drop dead carbon targets. What we haven’t discussed is, how we measure our journey to positively achieve those goals.

At renaissance, we use Revit: a designing and modelling software tool engineers use to create computer-assisted designs for building schemes. The platform allows us to take a very fine-grained approach to everything about a building design. From the structural grid to the foundations, we’re able to input each facet of all proposed materials into the design.

Once the design is complete, we can then extract all of this information to calculate how much carbon the proposed design embodies. To do this we’ve been developing our own calculation tool which takes all of the data we input from Revit, allowing us to customise elements such as concrete mix, type of steel, the distance the materials have to travel from our suppliers and so on.

After processing all of this data, the tool produces an accurate embodied carbon number of kg of CO2e per square metre.

How does this help?

Quite simply, by making use of the modelling software, we’re able to see how changes to a design can be reflected in the embodied carbon of a project. For example, rationalising the column grid of a scheme results in thinner floor plates and fewer transfer beams. Once this design change is added to Revit, we’ll see a marked reduction in the embodied carbon count simply because less carbon-intensive structural arrangements are being adopted.

Similarly, if we set the concrete mix to 60% GGBS across an entire development, there’ll be a reduction in the embodied carbon figure because it reduces the amount of cement needed.

In this sense, the software allows us to work towards efficient designs and for us to back up those design decisions with accurate data.

A concrete example

In Salford, we’re currently working on a residential tower for one of our clients. The concept design had been developed before our involvement and had an embodied carbon count of 273kg of CO2e per m2 (band D).

After redesigning different aspects of the core, structural frame and floor plates, we were able to bring that number down to 193kg of CO2e per m2 by Stage 3.

The importance of a scientific approach      

Global temperature rises are a real global concern and require serious solutions. For us to meet the challenge ahead of us, reform the way we operate and protect our planet for future generations, everyone must start making a difference in the here and now.

Only by monitoring the effects our designs have on the world and evaluating where we can make further changes, can we start to have a meaningful effect and make positive steps towards those important 2030 targets.

At renaissance, we’re well on our way to a better relationship with carbon, but we aren’t complacent. It’s a long journey requiring adaptation and considered forward-thinking to achieve a positive future for our planet.