Tristram Carfrae on carbon, materials and rebuilds

CARBON TRIGGERS DEBATE: When the UK’s leading architectural journal dubbed Tristram Carfrae, The Magician of Mass, a few years ago, they weren’t kidding.

Carfrae, who is an Arup Fellow and who’s won numerous prestigious awards, including the Gold Medal of the Institution of Structural Engineers for projects such as the “Water Cube” for the Beijing Olympics, Aurora Place, Sydney and most recently the completion of the Sagrada Familia Cathedral in Barcelona, is all about using less material, or carbon.

“As a personal view, over the last, let’s say, 30 years, we are putting probably 50-100 per cent more material into new buildings than is necessary,” Carfrae tells The Fifth Estate in an interview ahead of his appearance at the Carbon Triggers Big Debate on 25 August.

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We can go a long way to reversing this by being a “little bit keener to reduce carbon through reducing quantities of material,” he says.

This should be the central question that the built environment tackles, rather than whether to demolish or build new, he adds.

And particularly if the engineers could assure developers that a low carbon building needn’t cost any more than a high carbon building.

“In fact, if we do it right, it should be cheaper.”

And it’s all about the money, right?

Pretty much.

Back when the ESG framework was being developed Carfrae recalls a recent PhD graduate who declared the three circle ESG model was a bit “silly” because “nothing happens outside the economic circle”.

Thing is, says Carfrae, we use too much material; things can be cheaper if we think a bit more creatively about solutions.

Such as by a more thoughtful choice of grids – for floor plates of a building – and using “fewer, ideally no, transfer structures”.

In Australia our columns are too far apart, he says. If you put some extra columns in you can reduce the weight of the beams or slabs, which means less supporting material is needed in the structure.

“I’m not sure that our developer friends have ever been clearly told that actually, if you put [more columns] in, you’ve reduced the cost/material/carbon of the structure by 20 per cent.”

Thing is the agents tell developers that they need to meet the market; that tenants want huge open plan floor plates.

In the UK where he worked for years before relocating back to Sydney, Carfrae watched the local developer market lead government legislation in its attempts to minimise carbon.

“And that’s the change I saw in London, as the developers began to think, actually, that the agent may be only using retrospective data, historical precedent, and not thinking about what might happen in five years’ time or six years’ time when this building comes to market.”

Globally there’s a growing awareness that change is needed.

“I think the Europeans, with the EU legislation and movement, are ahead of the UK,” Carfrae says.

Denmark has a carbon budget, The Fifth Estate has learnt – as extreme as 5 kilograms per square metre for new residential development.

“The UK is also doing reasonably well. The UK has done it largely without legislation, without regulation. It dawned on everybody, it seemed to me, that carbon was a risk. In other words, if you were going to spend the next five years of your life delivering a brand new building that was full of embodied carbon, maybe it wouldn’t be worth very much in five years’ time, because no-one would want to rent it.”

The UK now has the London Plan across the entire metropolitan area, which requires a carbon assessment to accompany new builds.

Marks & Spencer – a high profile case study in carbon reduction

At one of the most high profile projects central to the debate on low carbon and demolition versus new build is the proposed redevelopment of the Marks & Spencer department store in London’s Oxford Street, the Arup team came up with a novel solution that finally got the project across the line.

“It was called in by government, but it then got redesigned by the same design team to be built almost entirely by reusing the material from the existing buildings.

“So, the idea is we disassemble existing buildings, and then we build it back out of components that we make from the existing, and that’s the current proposal.”

The Arup project director, Kerry Greaves, he says, has remarked that this single project has managed to turn everything she’d ever done as a structural engineer “upside down”.

Thing is, Carfrae says, that over the life of this single project, the world had changed.

“They had designed what they thought was a totally appropriate building…then found out that the ‘social environment’ said that was not appropriate or good enough.”

The original redevelopment plans came in at about 250 kilograms of carbon a square metre and the reconstituted ones will come in at 50 kg a sq m, Carfrae says.

But isn’t it generally more expensive to use old materials?

Not necessarily; there’s a lot you can do to minimise cost, and technology too comes into play, he says.

“You can cut up bits of stone, you can cut up bits of concrete, using computer controlled electric saws. Neither of these are difficult things to do now. So partly this attitude is legacy, but you do have to design around your material or whatever you have available.”

“The biggest message I could give you today is that engineers and architects, when they start a project, shouldn’t start by asking “what do we want to build?”. They should start by looking at what material is available from which we can build.”

Stone for instance

His work on the Sagrada Familia that’s been 144 years in construction, has led him to investigate the potential to bring back widescale use of stone as a building material that could solve some of our carbon problem.

Right now, he’s working with Gosford Quarries in New South Wales to find ways to create a nine metre by two metre wide “double T” made of post tensioned stone…just to show stone can do pretty much whatever concrete does, but with much lower embodied carbon, and is much more beautiful, of course.”

What’s important is projecting the total carbon over the life of the building – embodied and operational – and then having a plan for what to do with all buildings at the end of their life, as a citywide plan.

Stone used to be a utilitarian material, he says, then it became a luxury material for finishes only.

“I want to drag it back, so we treat it as a bit more of a utilitarian material again.”

But it’s expensive, right?

Not necessarily. “You can cut it with computer controlled saws nowadays. There’s less effort in cutting stone than there is in making concrete.”

And contrary to common beliefs, it’s also no more expensive to transport than concrete.

But his attitude to materials is agnostic. There are times when timber is appropriate, but it’s not going to replace concrete.

“In the end, we have to decarbonise concrete.”

But his biggest passion is LCA, or life cycle assessment.

What’s important is projecting the total carbon over the life of the building – embodied and operational – and then having a plan for what to do with all buildings at the end of their life, as a citywide plan.

But “what does good actually look like for a building structure – is it 150 kg a sq m or is it 200 kg, and what is it for a façade or a fitout?

“Getting that mindset is actually the key thing, rather than legislating it. Although, of course, legislating will bring the mindset along quite quickly.”

And we need to build buildings that people love and want to keep. There’s no merit in keeping buildings that people don’t want. “I don’t see re-use as a holy grail”

“There’s nothing wrong with mandating change,” he says, “but we shouldn’t wait for it.”

In London, the private sector led the public sector to transition the social licence, but lately the mood on sustainability has cooled.

He thinks it will turn again.

Why? we ask.

“Because we have to.”