Why do we keep building glass skyscrapers?

Despite criticisms about their environmental impact, glazed skyscrapers continue to spring up in cities around the world. Jon Astbury investigates why they remain so popular.

In 2011, British architect Ken Shuttleworth – who designed the Gherkin while at Foster + Partners – declared that "the tall glass box is dead".

He doubled down a few years later, telling the BBC: "We can't have those all-glass buildings. We need to be much more responsible." Speaking to CNN in 2018, he described a "sea change in attitudes" towards the typology.

"We created too many large expanses of glass"

Shuttleworth's is not a fringe view. In 2021, Morphosis partner Ung-Joo Scott Lee and Kohn Pedersen Fox president James von Klemperer also predicted the demise of the glazed tower in interviews with Dezeen.

"I think we all feel, as a community of architects, that we all created and had built too many large expanses of glass in our cities," said Von Klemperer.

For their proponents, glass skyscrapers remain one of the most powerful and economically attractive ways of staking a claim on a city and skyline.

But for their critics, they are gleaming symbols of all that is wrong with modern architecture and construction, representing the maximising of real estate regardless of how energy-guzzling or visually homogenous the results may be.

As pressure to decarbonise the built environment intensifies, the scrutiny is only growing.

Studies have shown that the environmental performance of glass buildings simply does not stack up. Nowhere in the world does it make practical sense to cover a building entirely in glass – they require air conditioning in summer and leak heat in winter.

"There's strong evidence we are over-glazing our buildings," said Phillip Oldfield, head of the school of the built environment at UNSW Sydney and author of The Sustainable Tall Building: A Design Primer.

"Most towers probably have a window to wall ratio of 50 to 80 per cent. Research suggests in office buildings in Europe, the optimal ratio is closer to 30 to 45 per cent – but this should differ on each facade," he told Dezeen.

"The trend, rather than being dead, is accelerating"

In spite of all of this, the sea change predicted by Shuttleworth, Scott Lee, Von Klemperer and others is yet to happen. In some places, the trend seems to point in the opposite direction.

A quick glance at the Council on Tall Buildings and Urban Habitat's list of the 100 tallest buildings under construction shows that most are all-glass, steel and concrete-framed skyscrapers, regardless of geographic location.

Even in New York City, where in 2019 then-mayor Bill de Blasio said that glass skyscrapers "have no place in our city or our Earth anymore", proposals for such buildings continue to emerge – including a design for a 487-metre-tall tower on Park Avenue by architecture studio Foster + Partners, unveiled in September.

"I think the trend, rather than being dead, is accelerating for two reasons," said Oldfield.

"One: glass curtain walling is incredibly successful as a building product. It combines all the basic performance requirements of the building skin (acoustic, thermal, solar, visual, et cetera) into one comprehensive product that can be quickly lifted on site and fitted into place – so it's an efficient and economical solution."

"Two: I think there's still a weird obsession with skyscrapers portraying a sleek, transparent aesthetic – a hangover from the modern movement," he said.

The history of the glass skyscraper is often told through this lens: that of a sleek, transparent emblem for technological advancement, openness and democracy borne of the modernist era.

Whether its origins are attributed to Charles Burton's tall, skinny reimagining of Joseph Paxton's Crystal Palace or Ludwig Mies van der Rohe's unbuilt entry to the Friedrichstrasse Skyscraper competition, the type is often closely linked to ideas of industrialisation and progress.

"Skyscrapers will probably always hold symbolic meaning," noted UK Green Building Council chief executive Smith Mordak. "For some they denote wealth and achievement, for others they signify inequality and misuse of resources."

"The best we can hope is that those contemplating building one are thinking about all these meanings when assessing feasibility in the round," they added.

Gap between architects and developers

Within its earliest examples were the seeds of glass curtain walling's problems. Glare and overheating in Paxton's Crystal Palace made its internal conditions notoriously unstable – to the point where sections had to be covered with canvas.

Mies van der Rohe's Seagram Building in New York – in many respects the original model for glass skyscrapers – made headlines in 2012 when it was revealed its energy-star rating was just 3 out of 100: the worst score of any building in the city.

But with glass curtain walls being so cheap to produce, install and maintain as well as offering an open interior with maximum daylight and views of the surrounding city, they became a no-brainer for developers wanting the best possible return on their sites.

Speaking in 2020 about his research into the carbon impacts of tall, often glazed buildings in London, UCL emeritus professor Phillip Steadman noted that developers "are much harder to convince" about the need for alternatives.

Now, a widening gap exists between some architects and their clients. For example, Robert Greenwood, a director at Snøhetta, is unequivocal about the Norwegian architecture studio's view.

"For our part, we do declare once again that the all-glass skyscraper is finally dead," he told Dezeen. "Commercially driven, this objectification of architecture seeks to celebrate what the building is, rather than what it does."

"Most locations will demand more of the building than that it stands alone as a reflective tower, glazed equally on all facades."

Nevertheless, Snøhetta still works on skyscraper projects that are predominantly glass, as do Morphosis and KPF.

New materials and technologies

New technologies that improve the thermal efficiency of glass curtain walling are continuously emerging, and proponents argue they see off the worst criticisms about unsustainability.

Indeed, Mies van der Rohe himself predicted the necessity of these developments, saying of his modernist glass boxes that it was "up to the engineers to find some way to stop the heat from coming in or going out."

"Technologically, recent improvements in glass systems have greatly reduced energy use, through an optimised approach to heating and cooling," Pelli Clarke & Partners partner Darin Cook told Dezeen.

The US architecture studio continues to build numerous all-glass skyscrapers worldwide, recently completing the Salesforce Tower in Chicago, but now tends to incorporate special coatings in the facade that reduce heat gain or integrate solar panels.

The most advanced glazed curtain walls are now composed of up to four layers of glass, such as Zaha Hadid Architects' glass skyscraper on what is reportedly the world's most expensive plot in Hong Kong, featuring four-ply, double-laminated, double-curved insulated glass panels.

But Oldfield has his doubts about this technical solutionism.

"My big criticism is we seem to be adding more materials and technologies to solve a problem that could easily be solved by simply using less glass," he said.

Additionally, while the advancement of glass panel systems helps to reduce carbon impact during the building's operational lifespan, these benefits can be outweighed by being far more carbon-intensive to create and more difficult to recycle.

"In practice, the recycling and re-use of complex flat-glass facade components is notoriously difficult," said Greenwood. "Today almost all glass materials removed from glazed cladding systems are typically downcycled or landfilled."

Mordak echoes these concerns. "To create buildings according to circular economy principles, things need to be made with reclaimed and recycled materials as much as possible, be repairable, and also be demountable and recyclable at the end of their lives," they explained.

"This can be more challenging when tall buildings need to be so highly engineered as to require very high-performance materials."

While glass itself is considered to have a service life of 60 years and up, the insulated panels common in curtain walling are thought to last between 25 and 35 years.

Upgrading these systems is possible. In the refurbishment of 1 Triton Square in London, for example, facade suppliers Scheldebouw removed the original glass curtain wall panels, refurbished and reinstalled them.

But as hundreds of tall glazed buildings reach "retrofit age", Oldfield is doubtful about whether this will be most developers' preferred option.

"Around the world there are some 944 office buildings more than 100 metres tall that were completed between 1953 and 1983, and are probably in danger of demolition," he said. "That's millions of tonnes of embodied carbon at risk."

Some architects do appear to be having success in convincing developers to go for a more contextual alternative to the all-glazed facade.

In particular, the US has seen a recent shift back towards the more solid facades that defined the earliest high-rises.

And even long-time designers of glass skyscrapers such as Pelli Clarke & Partners acknowledge the role of better suiting climates and conditions.

"While glass-clad towers will likely remain a staple of architectural design, designers are increasingly leveraging new materials and systems to better suit local climates and conditions, and in many cases, reducing the surface amount of glass and incorporating alternative materials," said Cook.

Detractors of the glazed curtain wall may view that as a small but hopeful sign of progress – but while the glass skyscraper might be dead in the minds of architects, for the many others who shape our cities it remains alive and well.

The top photo is by Antoine Pouligny via Unsplash.

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