OPINION

Will someone join the dots between the skyscraper boom and flooding?

17 JUNE 2024 ·BY CHRIS WISE
ARCHITECS  JOURNAL

Major cities like London will be hit by widespread flooding if the planet’s temperature rises by 2°C. And tall buildings are making things worse, says Chris Wise

The Evening Standard recently juxtaposed two headlines on the same page: ‘600 more London skyscrapers to transform city skyline’ alongside ‘Man the Barrier! Flood Wall to Rise’. The Standard went on to note: ‘Flood defence walls through London will need to be half a metre higher in the future to protect against climate change.’ The irony might have been lost on the editor who decided to run those two stories side by side. They were both about construction after all.

We’d have to be daft not to realise by now that 600 skyscrapers will make the climate and the flooding worse. Climate Central Statista Charts suggest over 10 per cent of the population of many capital cities will be affected by flooding if the global temperature rises by 2°C. In Kolkata (Calcutta), Mumbai, Hong Kong, and Shanghai, more than a third of the population will be affected. Skyscrapers consume new, raw materials at a rate eclipsing that of equivalent low-rise buildings of the same floor space, and the industrial processes of that production emit greenhouse gases and other pollution. One is now proposed in Oklahoma that would be 581m, making it the tallest in the United States.

Forgive the quick sums, but if you build a tower of 145 storeys (which I estimate the Oklahoma tower to be), its wind system needs to resist at least 24 times more bending compared with an equivalent group of low-rise buildings of the same total area, say six storeys tall. Try the tower’s columns: these get bigger in proportion to the number of stories they carry. A column at the bottom of a 145-storey skyscraper is 24 times bigger than you need for a six-storey building. Then there’s the extra material needed for long-span floors, where because of the fashion to avoid columns, we impose bending in a 12m floor span that is 180 per cent that of a 9m floor, and 400 per cent that of a 6m floor. All of this adds material, and all that material carries extra embodied energy which feeds back into the climate.

You don’t need to be an engineer to see that these towers consume far more material than lower-rise buildings during their construction, and most of that material is newly minted, often by degenerative means whose impacts go far beyond the mine, the dredger or the pollution of the concrete truck. Despite this, the Biden administration’s new guidance for Net-Zero buildings in the US only considers energy in use, ignoring the damage caused to the global environment by the actual building process and ignoring the enormous, embodied carbon emissions for which people like those in Oklahoma and their self-centred decisions are accountable.

Here in the UK, the government’s Future Homes Standard is equally imperfect, requiring homes built from 2025 to be ‘zero carbon ready’ – that is ‘the standard is solely concerned with energy efficiency measures, thereby only addressing the in-use operational carbon of buildings’. But this is nowhere near zero carbon because the embodied energy of the building’s construction is not covered. Why? Because, as our government went on to report, ‘engagement with industry on embodied and whole-life carbon to date suggests that, for large and small developers, measuring embodied carbon is “unfamiliar territory”’. There it is in black and white: we’ve decided to ignore embodied carbon out of … ignorance.

As those in the 600 new London towers look down on their cars floating away below, even as their basements flood and their lights short out (admittedly this saves energy), they can ask themselves why, in our hour of need, the government decided not to pay attention to the embodied energy of construction materials because it was ‘unfamiliar’.

Chris Wise is founding chair of Expedition Engineering and the Useful Simple Trust and a visiting professor at the Cambridge School of Architecture