A clear solution30 December 2020
Advances in coatings and structural glazing have enabled glass to dominate our contemporary city skylines, but glass facades continue to be controversial. What are the latest developments in terms of maximising the material’s attributes, and can glass expect to play a leading role in a future geared towards sustainability? Brooke Theis speaks to renowned glass builders, including Kees Kaan and Marco Lanna of Kaan Architecten, Make Architects’s principal Ken Shuttleworth, and Simon Sturgis, founder of Targeting Zero and ex-chairman of RIBA Sustainability, about what the future might hold for this polarising material.
City skylines tell a story of ambition and innovation. In the past century, glass structures have grown in the world’s capitals as part of the race to build taller and sleeker. From Moscow to Madrid, glistening skyscrapers have become a coveted symbol of industrial progress.
It’s a trend that has been gathering momentum ever since Mies van der Rohe unveiled his skeletal steel prototypes in 1921, inspiring a trend in 1950s America: the UN Secretariat Building in New York, designed in 1952 by Oscar Niemeyer and Le Corbusier, was the first all-glass skyscraper. This was closely followed by Lever House of 1954 and the Seagram Tower built in 1958, followed by the construction of countless others worldwide.
Our collective proclivity for transparent towers endures, with the erection of a $400m twisting glass tower in Dubai currently under way, and China’s $3.5bn museum and members’ club named ‘the Crystal’ opening soon. But there are concerns about the sustainability of such buildings, which absorb and trap heat in the summer and expel warmth in winter months, requiring vast amounts of energy to balance temperatures.
More recently, a number of prominent urban designers have spoken out about the overuse of glass in recent years, including the British architect Ken Shuttleworth, the founder of Make Architects. Despite being best known for his work with Foster + Partners in creating giant glazed structures, including London’s City Hall and ‘the Gherkin’, Shuttleworth now considers the liberal use of glass to be unjustified.
“Glass is the most energy-guzzling part of the building,” he says. “We need to save the planet, and the only significant way to reduce the consumption of energy in architecture is to reduce the amount of glass used.”
For Shuttleworth, working towards a carbon-neutral future means making buildings that are highly insulated and responsive to their environments, whether they are set in a rainforest or in a desert. “If you look at some of the buildings around London now, they’re still 100% glaze,” he says. “There needs to be a change of attitude to say, ‘We can’t do that, it’s wrong.’”
In the past ten years, glass skyscrapers in London, like ‘the Cheesegrater’, the Shard and ‘the Walkie-Talkie’, have risen – with the latter a cause of controversy in September 2013, when the immediate surroundings of the 37-storey building were damaged from the hot rays of sunlight it reflected. The Walkie Talkie has since been fitted with additional shading, and its developer, Land Securities, has learned from its mistakes – the company’s current project, the Zig Zag, has been consciously formed to remain cool, with alternate walls casting shadows on neighbouring structures.
It is possible, then, to reduce the amount of heat trapped by glass with the use of coating and tinting, but Shuttleworth explains that such treatments make the glass more complicated to recycle – recyclability being one of the material’s greatest virtues. “The coatings give you better short-term energy performance, but in the long-term it just becomes rubble.”
Problems with the material’s longevity don’t stop there. As Simon Sturgis, the founder of Targeting Zero and the ex-chairman of RIBA Sustainability, explains: laminated glass and double glazing typically have warranties of just 25 years. He describes the comparatively short lifespan of these materials and the need to regularly replace them as “an embodied carbon problem today. Failure of these units after no more than 30–40 years is highly wasteful, both of glass and the framing systems,” he says, adding that “society can no longer tolerate this short-term attitude to material use”.
Such damning analysis shouldn’t necessarily rule out using the material altogether, but spark thoughtful reflections on how best it can be used long-term. There are a number of ways to improve the carbon footprint of glass structures, as Marco Lanna, a senior project leader at the Netherlands-based practice Kaan Architecten, outlines. “When properly used, glass makes it possible to create microclimates that reduce the need for energy consumptions,” he says, pointing out that “more daylight decreases the use of artificial light”.
In his work at Kaan Architecten, Lanna explores the latest solutions to the issues of glazing, one of which the design group employed in its construction of the new terminal building at Amsterdam Schiphol Airport. “We designed a 19m-high, 200m-long glass facade, which was originally supposed to be triple-glazed. But, with our consultants, we activated the mullions framing the glass panes to neutralise heat and cold penetration. This simple trick allowed for a transparent facade that respects the highest energy standards.”
Invariably, glass buildings are popular not just because of their impressive appearance, but for their social worth. Transparent office walls mean workers benefit from natural light and can enjoy views of the outside, something that Kees Kaan, the co-founder of Kaan Architecten, considers to be crucial.
“The use of glass is extremely important in creating comfort and atmosphere in a building,” Kaan says. “Sunlight enables people to function, but also to have the awareness of changes of light during the day. So, in this sense, windows, glass facades and glass structures are fundamental to architectural quality. Without glass, there is no future for architecture.”
Kaan cites a number of his projects where glass has played a fundamental role in the intent behind the structures. For example, Kaan Architecten’s Supreme Court of the Netherlands has an entirely glazed ground floor “to establish a connection between the highly authoritative programme of the building and the street level, making it more accessible and visually open to the public”. Additionally, the designers decided to wrap the whole of the Chambre de Métiers et de l’Artisanat in Lille in a reflective double facade “as a panoramic curtain to articulate, absorb and reflect the surrounding nature”.
Shuttleworth agrees with Kaan’s view that it is essential for a building to have views of the outside and enable its inhabitants to feed off natural light. “You can’t just live in a bunker,” he says, “but you’ve got to be very clever about how you use glass: you’ve got to make sure you’re putting it in the right place for the right reason. You could, for instance, make the roof 5% glass and get perfect light inside a building, while 95% of the roof would be solid. Placing it at a higher level lets in far more brightness than, say, putting it below desk level.”
For their recent work on the New Bailey in Salford, Shuttleworth’s Make Architects practice was asked to attain a U-value (or thermal transmittance) of 0.3 and light transmission of 0.7 to maximise daylight, but Shuttleworth explains that almost no glazing products are able to achieve this, and the ones that do are extortionately expensive. So, the practice looked at maximising the self-shading of the building, by using solid panels and setting the glazing back. Additionally, his 5 Broadgate project in London is nearly 70% solid, and uses a highly insulated aluminium system with stainless steel. “It’s not the normal building you’d expect, but it paves the way for the future,” Shuttleworth says.
And the future belongs to those with the power to shape it, most notably governments that are becoming increasingly concerned by the longterm environmental impact of glass skyscrapers. In 2019, they were banned entirely in the place where the phenomenon began, as part of efforts to reduce New York’s greenhouse emissions. It’s a measure that is not to everyone’s taste.
“Our office fully favours this evolution towards sustainability, but we consider New York City’s ban a rather unnuanced policy, whose benefits can be reached without bans or proclamations,” Lanna says. Shuttleworth, on the other hand, disagrees. In fact, he would welcome a similar sanction in the UK. “The great thing about being an architect is that the more rules that are thrown at you, the more challenging it is and the more you can respond creatively to it. I don’t mind the rules being harsh. I don’t think banning glass is a bad thing.”
Although they may not agree on the best path to get there, Kaan and company concur there is an urgent need for urban planners to consciously and sustainably use glass.
In contrast to the elegant, clear towers that dominate our skylines, the battle for progress is not always a clean endeavour, but rather a messy exercise in balance and diplomacy. Future generations of architects will need to find new ways of using glass that stand for progress – rather than simply paying homage to it.