If we care about sustainability, should we still be building super-tall skyscrapers?

Studies show that taller buildings are simply less efficient, and don't even give you any more useable area. Why bother?

Writing in Curbed, Patrick Sisson asks In the supertall era, is the sustainable skyscraper a myth? We are going to be getting a lot more of them too; “the latest look at the global state of tall towers by the Council on Tall Buildings and Urban Habitat (CTBUH), suggests that the age of super-tall towers and expanding skylines is just beginning.” But Sisson wonders:

This new generation of towers, which represent the utilization of cutting-edge technologies, showcase great feats of engineering. But in a world slowly responding to climate change, can this type of construction, which requires massive amounts of energy and materials, ever approach sustainability?

There are new technologies that are being used to make tall buildings more efficient, from parametric design to innovative engineering. Regulation changes could help too.

A research paper by Christopher Drew, director of sustainability for Adrian Smith + Gordon Gil, a pre-eminent firm for skyscraper design, suggests that achieving a carbon neutral building is indeed a possibility. But buildings will likely only reduce their life cycle carbon emissions if regulations encourage them to do so. They suggest cities and countries begin to adopt new regulations, including: mandating Environmental Product Declarations, which establish embodied carbon value for building materials and make it easier to track and reduce embodied carbon emissions in construction; new building standards for sustainability that give owners marketing and bragging rights for greener construction; and zoning incentives from local planners that let more sustainable buildings add more floor space, which provides an economic incentive to cut embodied carbon.

But the whole discussion ignores a fundamental question: should we be building so tall in the first place?

The simple fact is that the higher you go, the more structure you need to resist wind loads and carry the loads, the more elevators you need, the more pumps to get water up to the top. A 2018 study, Energy use and height in office buildings, found huge increases in energy consumption as buildings got taller.

When rising from five storeys and below to 21 storeys and above, the mean intensity of electricity and fossil fuel use increases by 137% and 42% respectively, and mean carbon emissions are more than doubled….Newer buildings are not in general more efficient: the intensity of electricity use is greater in offices built in recent decades, without a compensating decrease in fossil fuel use. The evidence suggests it is likely – although not proven – that much of the increase in energy use with height is due to the greater exposure of taller buildings to lower temperatures, stronger winds and more solar gains.

The study authors also looked at residential buildings and found that gas and electricity use increased with height. Finally, according to Physics.org, they looked at building form, something we did recently in TreeHugger.

A third part of the study looked at the relationship of different forms of building to their densities, where density is measured by taking the total floor area and dividing by the site area. The work has shown that, in many circumstances, the densities achieved by tall towers can be achieved with lower-rise slab or courtyard buildings. It is not always necessary to build tall to achieve high densities and energy use could, in many cases, be greatly reduced by building in different forms on fewer storeys.

Another study that one of my students found, Life-Cycle Energy Implications of Downtown High-Rise vs. Suburban Low-Rise Living looked at residential buildings and found a similar result: The higher the building, the less energy efficient it was.

© Waugh Thistleton Architects/ Dalston Lane

Sisson mentions that architects are becoming more concerned about embodied carbon, and mentions that architects are looking at super-tall wood structures. But this creates structural problems of a different kind; the wood structure is so light that it has to often be loaded with concrete to hold it down, like they did in Norway. That's one reason Andrew Waugh designed Dalston Lanes the way he did, wide, low and castle-like. Clare Farrow wrote in Dezeen,

Andrew Waugh's argument is that we don't necessarily need to be thinking of wooden skyscrapers in London, however seductive the concept is, but rather of increasing density across the board. He is thinking more in terms of 10-15 storey buildings, which many believe to be the comfortable height for human beings.

I admire the people behind the Council on Tall Buildings and Urban Habitat, I have met them a few times at conferences. I get the idea that they want to make our super-tall buildings more energy efficient.

But we really care about sustainability and energy efficiency, a better option is to not build them at all.