Death to the Skyscraper: Skyscraper construction, and the financial system that underpins it, is not stopping any time soon, despite its detrimental impact on the environment

Taking example numbers from the article, but not explicitly stated, it kind of sounds like 15 floors, about 60m tall, is the point in which density starts to sacrifice ecological concerns too much.

According to a 2015 study commissioned by the CTBUH, the whole life emissions of both energy use and materials for a 120m concrete and steel structure are nearly five times higher than those of its 60m equivalent.

That's still tall enough for many things, so I guess the rest should be handled by a bit more space use and better mass transit.

Even at city level, the huge carbon cost of skyscrapers fails to outweigh any potential benefits that they might achieve from restraining urban sprawl. A study in npj Urban Sustainability in 2021 showed that the most carbon-efficient way for cities to grow is by developing densely built low-rise environments. The carbon cost of taller buildings is greater than carbon savings from restricted land use. This means that high-density low-rise cities such as Paris are more carbon-efficient than high-density high-rise cities such as New York.

I am...doubtful. I'll need to see the data. The article repeatedly makes the mistake of comparing the ecological impact of a bigger building with the ecological impact of a smaller building, which is of course ridiculous. It also makes mention of the decreasing efficiency of materials as height increases, which is valid. But to say that skyscrapers are SO inefficient that it's better to sprawl? That runs absolutely counter to everything I've ever heard.

Edit: I found a more in depth discussion of the study here https://www.bloomberg.com/news/articles/2021-08-25/to-cut-carbon-think-low-rise-buildings-not-skyscrapers

Three takeaways

For a city supporting 20,000 people, moving from low rises to high rises without changing the density results in 140% more carbon emissions. For a city of 50,000 people, the increase is slightly lower, at 132%.

Well...duh. Same number of people, more material, greater carbon footprint.

In scenarios in which researchers observed the number of people each typology can house in a given amount of land, they found that high-density, low-rise cities on average can support more than twice as many people as high-density, high-rise cities without increasing carbon emissions.

This is the part that I was doubtful about, but the article makes a good argument and the data sounds solid. Contributing factors are an increase in the urban heat island effect, and skyscrapers requiring a bigger empty space between buildings.

Arehart is careful to say that the study focuses solely on building emissions, and doesn’t account for other factors like transportation, design or the type of land cities build on, which affect their carbon output. More study is also needed to confirm if their conclusions still hold true for increasingly larger populations.

This is why I think the original article jumped the shark by saying that "The carbon cost of taller buildings is greater than carbon savings from restricted land use." First of all, they didn't study that directly. And second, they explicitly didn't study the main factors increasing carbon footprint in sprawling cities. I think the Bloomberg article gives a much more reasonable and correct picture: density is always better, but low rise density is better than high rise density.