Two cars, a lemon, and a bottle of Lucozade: just a few of the objects that have been melted by Londons Walkie Talkie building. But the heat radiating off the glass towers awkwardly angled 160-metre-tall walls isnt the heat we should be most worried about. The Walkie Talkie, like all glass skyscrapers, is warming up the world in a much more all-encompassing way. This is now a climate emergency, says Diana Ürge-Vorsatz, professor of environmental sciences and policy at the Central European University in Hungary and member of the Intergovernmental Panel on Climate Change (IPCC). She believes all-glass skyscrapers should be banned. If we want to reach any reasonable climate objective, I dont think we have any other option. Any building playing host to hundreds of people is going to have a huge climate footprint, but the glass is particularly problematic. The sunlight has unlimited access into the building, but no way to get out. With an all glass building, youre fighting the environment rather than working with it, says Simon Sturgis, who is an adviser to the government as well as chairman of the Royal Institute of British Architects sustainability group. Conventional glass skyscrapers are just tall green houses. The heat inside cant escape because the whole structure is wrapped in a glass skin. Thats great for tomatoes, but for people it just means more air conditioning. The amount of energy used for cooling has more than doubled since 2000, and it will double again by 2040 if we dont curb our reliance on air conditioning, according to the International Energy Agency. Even in a moderate climate, cooling issues are becoming more and more severe, and the proliferation of glass buildings is accentuating that fact, says Henrik Schoenefeldt, senior lecturer in sustainable architecture at the University of Kent. Its a vicious cycle: we build a glass skyscraper, then have to cool that glass skyscraper, which uses energy, which contributes to the climate crisis, which increases the temperature. The hotter weather makes the glass building even harder to cool, but we have to keep cooling it because sweaty co-workers are not happy co-workers, and so the cycle goes on. This problem cant be solved by just turning off the AC. We dont want people to sweat in overheated buildings, thats not the point, Ürge-Vorsatz says. The point is that with responsible architecture you can keep people cool without unnecessary cooling. We need to build better buildings. Conventional glass skyscrapers are sealed up, so theres no natural ventilation. But architects have developed a way to add windows to the coveted glass aesthetic. You can make efficient buildings that are highly glazed, but it requires a lot of effort technologically and you have to think about how the building is layered, Schoenefeldt says. The RHW.2 office tower in Vienna has two outer glass walls with a cavity between them, so the inner windows can be opened to get some fresh air. They have maintained the prism aesthetic but made it more environmentally conscious with the second skin. The Austrian office block uses just 20 per cent of the energy a similar-sized conventional glass building in the UK would use, he says. And, while the towers £800m price tag is £4.6m more than a less-innovative version would cost, the extra upfront amount was recovered after four years of use. The buildings are so efficient you can make real economic savings in the operational costs, says Schoenefeldt. Many modern glass skyscrapers use this construction technique, as well as other technological advancements such as blinds that automatically adjust to block sunlight from entering the building. It sounds like the perfect, technology-focused solution. But its not, Sturgis says. Cutting down cooling isnt enough to redeem these glass structures. This facade is designed to reduce cooling load but the problem with it is its very high in embodied energy, he says. Embodied energy is the energy it takes to make the material. Timber has a low embodied energy because it actually pulls carbon out of the air as it grows, whereas glass is very energy intensive. While Sturgis concedes that these layered facades lessen cooling issues, he points out that glass doesnt last a lifetime. The glazing needs to be replaced every 30 to 40 years, he says. That creates a big carbon problem. And the glass panels are stuck together with plastic, so even recycling them is difficult. Really, its our obsession with tall glass boxes thats the issue. Glass is great for making windows, but when it comes to the rest of the building, even with innovative solutions, it cant compete as a sustainable material. And that just wont cut it anymore. Yes, glass is beautiful, but in the 21st century when we face a climate emergency, we need to redefine aesthetics, says Ürge-Vorsatz. A building can be beautiful without being, from a climate perspective, extremely irresponsible. Bio-based materials like timber provide a better option. In Vancouver, an 18-storey students’ residence building was built out of timber in 2016. The project redefined the height limits for wooden buildings, and a new 40-storey timber skyscraper is under construction. It will be a zero-emissions building and that should always be the goal. If youre building a very tall building you should expect it to last a hundred years, so surely you should be taking into account the climatic change that is going to happen, says Sturgis. If you dont factor that in, youre stuck with that error for a century or more. Theyre lock-in risks, says Ürge-Vorsatz. Once you build a skyscraper it pre-determines our emissions for decades to come, so we definitely need legislation in this area. Some restrictions are already being discussed and implemented. New Yorks major Bill de Blasio called for a ban of all-glass skyscrapers earlier this year. Hes already converted to a heavy criteria rather than banning them outright, says Sturgis, but the fact that hes fingered them as being a problem is very interesting. As awareness of the environmental issues linked to these buildings goes up, they will become more of an investment risk. The Bank of England is going to start stress-testing financial institutions for climatic risk in two years time, says Sturgis. One thing they dont like is financial risk, and if all-glass buildings are perceived to be risky in a climate sense, you can only see this going one way. As the world moves towards a zero-carbon target, glass skyscrapers will be forced out of fashion by investors who see them as a risky investment and brands who dont want their sustainably minded customers to judge them by their offices carbon footprint. The skyscrapers of the future will still need windows, but glass should be 40 per cent of the facade, at most, and long-life materials will make up the rest. Think more Empire State Building, less Gherkin. Its pretty simple, but thats the key. Sustainability is about going back to basics, and not depending heavily on complex technology, says Schoenefeldt, and thats impossible to achieve when a buildings inhabitability is dependent on air conditioning. When Crystal Palace was built in 1850 for the Great Exhibition, the giant glass structure didnt have the luxury of air conditioning and it was a disaster. Giant sheets had to be draped over it to prevent visitors from melting. The fact that glass structures havent progressed far from that point is a big hint that theyre not the future. As Sturgis says: If youre going to build a tall building, theres a better way to do it than all-glass.
Wired, 11 November 2019