The Key to Green Building Is to Use Less Stuff

Making cement emits a lot of carbon dioxide: Every year more than four billion tons of cement are used to build highways, bridges, apartments, and office buildings. Steel is just as bad, with 1.6 billion metric tons produced in 2020 cranking out three billion metric tons of CO2. Together, steel and concrete are responsible for 15% of global carbon emissions.

Nobody seems to be doing much about this. Each new day brings another announcement of a highway widening or a new tower. All of which is solid embodied or upfront carbon—the carbon emitted making the materials. It is all going into the atmosphere now; every project is a big burp of carbon banging against the carbon budget ceiling.

This is why it is so important to build green and also to build less ... starting right now.

It is a subject we have discussed before, with the World Green Building Council's report "Bringing Embodied Carbon Upfront" that showed the wonderful chart of project development stages. The top one is "build nothing," followed by building less, building clever, and building efficiently.

But others have been saying this too. Will Arnold, the head of climate action at The Institution of Structural Engineers in the United Kingdom, wrote an article that "discusses the conflict between the need to build and the need to reduce resources, and how engineers can construct whilst keeping the environmental impact to a minimum." This is probably more natural for an engineer than an architect; engineers have been trained to do more with less.

Arnold first explained that, yes, "buildings are a good thing" since "they bring people together, keep them warm, and give them places to be useful." This sounds silly and obvious, but it has to be said. Just read the comments to some of our earlier posts that accuse me of wanting everyone to live in mud and thatch huts and stop all progress.

Arnold continued: "We can’t just stop construction altogether though – as we need more buildings and infrastructure (more so in some parts of the world than others). So instead, we must learn how to construct while minimizing our damage to the environment."

He then explained embodied carbon—or my preferred term, upfront carbon—and why it matters now:

"Historically, most of the carbon emissions from buildings have been due to their operation (heating, lighting, cooling, etc.) However, this is changing. There are plans for reducing these emissions–electrification, insulation, and generation on site–so the largest contributor to a modern building’s emissions is the materials used in its creation–the embodied carbon."

Arnold took all those little steps we previously and consolidated them into a simple rule that can apply to buildings or to just about anything in life: Use less stuff.

He even gave us an equation.

"Most approaches to reducing structural emissions fall into one of two types of action. You can minimise the amount of material that you use (put simply: use less stuff), or you can minimise the amount of carbon released when producing those materials. These also form the two parts of the equation describing embodied carbon emissions:

Embodied carbon = (quantity of material) × (carbon intensity factor)"

So you first try to use less stuff. Arnold wrote: "Our massing, layout and configurations must get more efficient (we often need to convince others to enable this), and then our design methods and utilisations must deliver this with no ‘spare fat’." Then you pick materials with the lowest carbon intensity. This is where most structural engineers have influence and impact, and so this is where the focus should be."

Writing for the World Green Building Council, engineer Scott Brookes of Ramboll picks up on the story and makes the case for building (next to) nothing. In addressing the first point—build nothing—he wondered if the world has changed post-Covid, where we live and work has become more fluid.

"Before Covid, working from home was rare; now it has become completely normal," Brookes wrote. "This shows that we can rapidly adjust our relationship with the built environment should it be required." Maybe we don't need all this new space but can reconfigure what we've got.

He then addressed the second point—build less—which is counterintuitive if you are an architect or an engineer who is often paid, if not by the pound, but by the size of the contract. Instead, he said, "By supporting a reduction in development, we reinforce the value of our consultant’s thinking time, innovation and design creativity."

Brookes also acknowledged that the world is changing and that while embodied carbon is ignored now, it won't be for long.

"We analyse more, to build less. In the not-too-distant future, embodied carbon in building projects will incur steeper taxation and new-builds will have a carbon cap. The best way for us to futureproof our client’s portfolios – and help the planet – is to keep abreast of this regulatory and taxonomy landscape, reduce as far as possible the requirement for new-build and anticipate the future demands on existing building portfolios, including alternative uses."

Then the PhDs at Preoptima pitch in. They produce software that is a "carbon hub" tracking both embodied and operating carbon. They do their own take on the Build Nothing step: "When looking at existing buildings, the three magic words are retain, retain, retain. Think critically as to whether building more or building new is the answer. Do we need to use new materials at all? Remember that building nothing eliminates the potential for embodied carbon emissions."

They also note that we all have to do this now and that time is not our friend.

"Critical to all of these principles and guides are the components of time and measurement - the sayings “it’s better late than never” and “what you don’t know won’t hurt you” definitely do not apply well to reducing embodied carbon in buildings. This is because addressing embodied carbon too late in the project often means it can not and will never be reduced."

This is why I prefer the term upfront carbon to embodied carbon: because time matters and these emissions are not embodied in anything, they are upfront. Their timing is critical.

We are already addressing embodied carbon too late. We are already banging up against the ceiling to stay under 1.5 degrees of warming if we haven't busted it already with the projects on the boards now. Carbon Brief's latest analysis has 260 gigatonnes left in it for a 50% chance of staying below 1.5 degrees, and we are adding 40 gigatonnes per year.

It's why everyone in the industry has to remember those three words: Use less stuff.