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A Growing Concern About Embodied Carbon in Glass Covered Skyscrapers

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There was a time when buildings had windows. Most large buildings built before 1850 were designed much like our homes, with opaque walls dotted with windows. Those windows help bring light into buildings and unlock a large part of the value of tall buildings, the view. For this reason they kept getting bigger and bigger. But in 1850 architects had a novel idea, what if the entire building was covered with windows? That way the views would be better (“floor to ceiling”) and the look of the buildings would be much smoother and more appealing to the changing aesthetic tastes which preferred clean lines to the cluttered adornment of the past.

One of the first buildings to try this design was The Crystal Palace in London. It was built not by an architect but by a gardener, who used his experience building glass hothouses. There were concerns with the idea right away since hothouses tended to get, well, hot, even in the cold British climate. Tomatoes might do well in the heat but people, especially with the long thick garments that were popular at the time, do not. To help keep the large glass building cool thousands of louvers were installed that needed to be opened and closed manually multiple times a day. A huge shade cloth was also draped over the sunny side of the building at times. 

The idea of covering buildings with glass caught on quickly, thanks to advances in air conditioning that allowed buildings to be cooled to combat the heat that the glass let in. Glass has also seen a lot of innovation, allowing it to be stronger and more thermally efficient and making it a better candidate for facades. Now that almost every new skyscraper is covered in glass, it has become the iconic look that we associate with modern buildings. New advances in glass technology have made it possible to change the tinting of glass that can even allow it to let in heat when the building needs it and block the heat when it doesn’t. In addition, more glass allows for increased daylighting which can potentially save some energy use inside the building.

But there are reasons why glass might not be the best option for a building’s facade. Most glass covered buildings don’t have windows, meaning that they can not be opened and closed. This makes regulating a building’s temp much more energy intensive (many buildings run AC even if it is cold outside). Not being able to open windows means that buildings recirculate most of their air, something that we all became acutely aware of during the pandemic. Even now that the threat of a deadly airborne virus has faded, there is more and more talk about the negative impacts of poor indoor air quality created by poor ventilation. 

What might be an even bigger problem for glass buildings is their environmental costs. Glass is produced with incredibly high heat, which requires a lot of energy. Glass buildings are only possible thanks to the steel structures that they are attached to, which also takes a lot of energy to produce. Also, it seems obvious but it is important to remember that much of the glass covering buildings does not need to be there, it is covering the floor plates that don’t need the light. Connecting the glass panes together is only done in order to prevent the lines that would break up the smooth look of the building (heaven forbid).

Currently, architects and developers do not have to report on the “embodied carbon” that their designs represent, but that may be changing. In 2019 former NYC Mayor De Blasio even said that he would “introduce legislation to ban classic glass and steel skyscrapers that have contributed so much to global warming.” While he was not able to pass such a ban the sentiment continues to grow as more environmental scrutiny is put on our building stock. If we do see a push to make buildings that are more energy efficient and have less embodied carbon we might start to see designs that have less glass or even exterior shade structures and curtains. Windows will always be a part of buildings but we will likely start to rethink the need to cover all of our large buildings in glass.



One thing I did not explore in today’s article was the way that glass skyscrapers can magnify the sun and thus the effect of urban heat islands. Here is a really cool interactive map that shows the heat island effect in NYC.


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