Is sustainability of vertical cities just a fad?

By Jan Dolezal

In many discussions and articles, “sustainable cities” and “vertical cities” are used almost as synonyms and many imply that floor-space-ratio correlates with sustainability. In this post I present arguments to challenge this popular belief.

Look at China for example. Shanghai Tower – the world’s second tallest building under construction boasts to be “sustainable best practice” and Broader Group’s Sky City which would become world’s tallest building is all intended as a role model of replicable sustainability.

Yes, there are clear energy efficiency advantages of going vertical. Less surface area per usable floor space results in less heat loss and less material required for enclosure. Large scale HVAC systems are more efficient. High density reduces the need for transportation.

But there are also numerous disadvantages to offset the gains. Bottom floors need to carry the full weight of all the upper floors, resulting in significantly more materials for primary structural systems. High buildings require extensive foundations to achieve stability in high winds and earthquakes, which drives material requirements further up. Less surface per floor space may result in less natural light. Smaller roof area versus equivalent horizontal buildings provides fewer opportunities for solar installations. Smaller parcel area does not provide opportunity for geothermal heating and cooling, which can sustainably reduce energy demands of a family house by 40-70% with ~10 year payback. Vertical transportation also requires additional materials to build and energy to operate. Given all these drawbacks the real resource efficiency advantage of vertical construction is at best questionable.

Sustainability is however not only about resource efficiency. Vertical construction poses other environmental challenges. One is visual contamination of high-rise buildings which prompted some place such as Hawaii, Washington DC or Canary Islands to impose limits on height of buildings. Increased stress on soil leads to sinking of many dense centers (e.g., Manhattan) that can hardly be called sustainable.

We can question sustainability of vertical construction even under current conditions, but what if conditions change? Is it really robust? We now live in time of relative peace, but how sustainable is vertical construction in times of war? Super tall buildings are most vulnerable and an easy target as we have already seen in the case of 9/11. Even if enemy does not destroy the whole building, how safe is it in case of a big fire? What if for any reason the electricity grid fails and people are stuck on 200th floor? If generators run out of fuel, how do we pump water to that height? Can you imagine the social unrest if for any reason (war, natural disaster…) supplies for such a building are interrupted? Horizontally distributed city of well insulated single family homes that have own geothermal heating, solar system, can revert to using wood in a fireplace and grab some food in own garden seem like a way more robust sustainable solution.

I don’t want to suggest that everyone lives on a self-sustaining farm, but I protest against implying correlation between verticality and sustainability. Perhaps the optimal solution is somewhere in between, such as 8-story modular buildings?

Image source: http://www.tdrinc.com/images/photos/large/Towers04a1.jpg

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3 thoughts on “Is sustainability of vertical cities just a fad?

  1. This conversation of “vertical cities” also hits at the core of a question Professor Macomber asked in the first class session: what makes a “city”?

    I think vertical cities are often conversations of the urban fantastic cloaked in sustainability. Your points about additional (and otherwise unnecessary) structure are right on, as well as a myriad of other systems that quickly outgrow their economies of scale at these kinds of heights.

    Truly, the very thing that these mammoth buildings are trying to leverage toward sustainability–height–is the very thing that prevents it. I would argue instead that the economies of scale that this type of colossal structures are trying to achieve could be much more effectively done by laying this same building on its side. If one were to really attempt to create a singular building (or perhaps interconnected set of buildings, but that’s essentially how megatowers are anyhow), you could achieve the same or better envelope material efficiencies, save massively on structural costs, come out way ahead on utilities and HVAC–and best of all, one wouldn’t have to use an over-burdened electrically-powered elevator to move about, but instead could walk (or use a specialized rail more efficient than elevator stacks).

    It’s a lot less sexy, but the opportunities for sustainability are far greater when you leverage the natural advantages that horizontality affords you. To me, a core issue of “vertical cities” is that they realistically will not be truly self-contained, but rather people from the surrounding urban areas will commute to it, and people who live in the towers will encounter their careers out of it. If the only intersection point for this “vertical neighborhood” (perhaps a more accurate term) is a singular ground floor, it brings with it an enormous number of functional challenges. A horizontal effort (imagine four to six floors in height; Paris-esque?), while admittedly begging a certain question about the comparative land requirement, affords many more points of intersection with the world around it–points that from an urban and real estate point of view are very valuable.

  2. The role of ego in the human desire to build to ever-increasing heights is timeless. Jan, your questions serve as a check towards ensuring that society’s love of progress does not usher in a modern day Tower of Babel. I question whether fear of war or terrorism suffice as reasons to shy away from vertical expansion, but ignoring the sinking of dense centers is a consideration we ignore at our own peril.

    While I agree it is important to think critically about vertical cities, I take a different view on some of your observations. For example, one person’s visual contamination of a city landscape is another’s feat of architectural artistry (New York by Gehry is a skyscraper that has been cited as both). Tall buildings do not have necessarily have less natural light due to structural or surface area constraints. Entertainment venues such as Boston’s Top of the Hub and New York’s Top of the Rock take advantage of the ability to feature expansive glassed in views of the city (natural light may, however, be blocked by other buildings). These buildings do experience greater wind speeds and may able to use wind turbines as an additional source of sustainable energy. With regards to energy conservation, I would suspect that heating/cooling an apartment is more efficient than a single-family house because the area of space to be climate controlled is smaller.

    One of the key positives of tall buildings is the ability to build a strong community within a small self-contained space. Admittedly, I am biased. Tall buildings are my status quo because I have mostly carried out my life in them. My senior homeroom was on the 13th floor of a one-building school, I lived in an apartment on the 12th floor and I worked on the 62nd floor of a building with an extensive tunnel network. To your question of safety and security, I think residents of vertical cities prepare for disaster much the way that others do. You practice – my school could evacuate 700 students down 13 flights of stairs in under seven minutes, even if one staircase or one floor was “blocked” and we had to find another route. You prepare – filling bathtubs and stocking up groceries before a storm much as Boston did for Hurricane Sandy. You improvise – during the blackout of 2005, when one of the electricity grids supplying New York failed, people helped each other up and down dozens of flights of stairs, carried supplies and borrowed from neighbors.

    To be sure, buildings require evacuation and safety redundancies as many of the studies following the attack on the twin towers noted. Some buildings use modular elevators, staircases and multiple sprinkler systems to begin to address this question. I wonder if these systems could be expanded to meet some of the standards of self-sufficiency you are suggesting? In theory, could we build a 200 story building in which every unit of 10 floors is self-contained with regards to plumbing, electricity and community needs?

  3. By John Macomber

    Maybe there is a balance here between efficiencies and the scalar nature of density in cities… (post by Jonah, comment here: https://sustainablecitiesfinance.wordpress.com/2013/03/03/smaller-cheaper-everywhere/comment-page-1/#comment-108

    …and the ego-ism of supertalls? The glitz and glamour of extreme verticality is related to posts about appearance by Jessica and by Cody:
    https://sustainablecitiesfinance.wordpress.com/2013/03/03/kenyas-new-konza-city-golden-goose-or-white-elephant/
    https://sustainablecitiesfinance.wordpress.com/2013/03/04/brand-new-sustainable-city-in-central-africa/

    One wants to find some optimum point between the endless sprawl of very non-dense Delhi, the sardine packaging human-warehousing mid-rise housing of 1950s New York, 1960s Hong Kong, or 1990s Shanghai, and the far from efficient 100 story plus towers on the drawing boards.

    There seem to be effective break points with respect to structure, mechanical systems, and elevators at about 6 stories, 20 stories, 40 stories, and 60 stories. These are common multiples for buildings that are mainstream bread and butter investments. One sees a lot of market housing at 6, 20, and 40 and a lot of office buildings in New York and Chicago and Mumbai and Singapore at 40 and 60. Naturally this is also studied by engineers looking at the economics (or lack of same) in supertalls (below)!

    Council on Tall Buildings and Urban Habitat:
    http://www.ctbuh.org/AboutCTBUH/tabid/483/language/en-GB/Default.aspx

    Thornton Thomasetti, structrual engineers for many of them:
    http://www.thorntontomasetti.com/services/building_structure/supertall_buildings

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