The Problem With Skyscrapers

Michael Mehaffy writes that there is growing research that paints a decidedly mixed picture on the benefits of tall buildings.

There are significant negative ecological impacts of tall buildings, as well as other negative factors, and the ecological benefits are not as great as is often assumed, says Mehaffy.

"Often cities like New York and Vancouver are cited as stellar examples of dense ecologically superior cities with tall buildings. It's usually assumed that it's the tall buildings in these cities that give them the edge.

These cities are indeed very positive when it comes to carbon and other ecological metrics. But it's often overlooked that tall buildings are only a fraction of all structures in these places, with the bulk of neighborhoods consisting of rowhouses, low-rise apartment buildings, and other much lower structures. They get their low-carbon advantages not from density per se, but from an optimum distribution of daily amenities, walkability and access to transit, and other efficiencies of urban form."

Thanks to Robert Steuteville

Full Story: More low-down on tall buildings

Comments

Comments

High-Rises and Global Warming

Thank you, Michael, for writing this important article. I will summarize the key points about the effects of high-rises on the most important environmental issue, energy consumption and global warming:

High-rises do not have significant environmental benefits compared with traditional European urban densities. When you go above about 50 people per acre, the density of traditional mid-rise European cities, you get diminishing returns in terms of reduced automobile use. International comparisons show that per capita VMT declines dramatically when you compare low-density American cities with European cities, but declines much more slowly when you compare European cities with high-rise Asian cities. Reduced automobile use is the most important environmental benefit of high densities, but you don't need high-rises to get this benefit; traditional European cities are very walkable.

High-rises have significant environmental costs compared with traditional European densities, including (if I may quote the article):
--Increasingly high embodied energy of steel and concrete per floor area, with increasing height
--Less efficient ratios of common walls and ceilings to exposed walls/ceilings (compared to a more low-rise, "boxier" multi-family form — as in, say, central Paris)
--Significantly higher exterior exposure to wind and sun, with higher resulting heat gain/loss

It is plausible that these extra energy costs of high-rises outweigh the energy savings of reduced VMT, so that traditional European-scale neighborhoods are more climate-friendly than high-rise neighborhoods. We need some precise quantitative work on this issue.

In addition, the article mentions the psychological and social costs of high-rises. In my mind, these costs are important politically: most people recognize these costs intuitively and are put off by high-rises, so there is likely to be far more political support for smart growth on a traditional European scale than for high-rises.

Thanks again for writing this important article. I hope it starts a national discussion of the issue.

Charles Siegel

Irvin Dawid's picture
Correspondent

March Atlantic Mag' features 'Skyscraper' article by Ed Glaeser

How Skyscrapers Can Save The City. Would be interested in reading reviews or comments by Planetizen readers....
Irvin Dawid, Palo Alto, CA

Edward Glaeser on Skyscrapers

Glaeser is an economist. Throughout his writing, he has shown that he is interested in cities as generators of economic growth, and that he is interested in skyscrapers as generators of faster economic growth. He admits that we need to balance growth with preservation, but he makes minor concessions to preservation and always comes down on the side of growth.

Any talk about urban design or about skyscrapers being "green" is just ancillary to this main concern. If he really cared about the environment, he would join the ranks of economists who are beginning to question the value of economic growth (such as Tim Jackson and Peter Victor).

Let me criticize the basic points of his article, as they are summarized at the beginning:
"Besides making cities more affordable and architecturally interesting, tall buildings are greener than sprawl, and they foster social capital and creativity."

--- Highrises do not make cities more affordable. They have much higher construction costs than 5- or 6- story buildings.

--- It is questionable whether highrises make cities more architecturally interesting. There is a body of theory that I consider convincing which says that you get the best urban design when you have a consistent urban fabric, with only important public buildings rising above the fabric.

--- Highrises are, in fact, greener than sprawl, but Michael Mehaffy's article shows that they are probably less green than traditional urban scale neighborhoods. Glaeser uses sprawl as a straw man.

--- When he says that highrises foster social capital and creativity, he is using economist's code words meaning that they foster entrepreneurship and economic growth. Paris was very good at fostering creativity in the 1920s, before it had highrises, back when Hemmingway, Gertrude Stein, and Picasso lived there. But when Glaeser talks about creativity, he is thinking of high-tech entrepreneurs, not of novelists, poets, and artists. Of course, high-rises are also not needed by high-tech entrepreneurs: Silicon Valley has done pretty well without them. Highrises seem to be destructive to important forms of social capital, such as public life.

To show how little Glaeser knows or cares about urban design, I refer you to his NY Times opinion piece saying that Jane Jacobs supported a height limit of 5 stories, and to my comment with quotations from Jane Jacobs showing that she favored a diversity of building heights, including highrises, which are at http://www.planetizen.com/node/44077

It is appalling that someone who has written a book about the city makes such a fundamental error about one of the most important writers about the city. Glaeser's saying that Jane Jacobs believed in a height limit of 5 stories is roughly equivalent to someone writing a book about economics and saying that Adam Smith believed that the government should control prices.

If someone wrote that, you would know that he has no interest and little knowledge of economics, and that he is writing a book about economics to advance some other, unrelated agenda. Likewise, Glaeser has shown that he has no interest and little knowledge or urban design or environmental issues, and he is talking about them to advance some other agenda.

Charles Siegel

Michael Lewyn's picture
Blogger

Talking past each other

It seems to me that Mr. Siegel and Prof. Glaser might not be so inconsistent as the former thinks. How so? Because I think they are addressing different issues.

Mr. Siegel and Mr. Mefaffy are comparing skyscrapers to an ideal world of dense rowhouses, and suggesting that a consistently rowhouse-oriented city would be more environmentally friendly to one with more skyscrapers.

Mr. Glaeser is comparing more skyscrapers to more sprawl, and suggesting that the former is more environmentally friendly than the latter.

It seems to me quite possible that both propositions could be absolutely right.

Sprawl, Skyscrapers, Traditional Cities

I agree completely that both propositions are right:

Skyscrapers are more environmentally friendly than sprawl.

Traditional European neighborhoods are more environmentally friendly than sprawl.

That still leaves us with the question of whether we should counter sprawl by building skyscrapers or by building traditional European neighborhoods.

This is the question that Mehaffy addresses, and this is a question that Glaeser ignores (as he generally ignores urban design issues) by using sprawl as a straw man and neglecting the possibility of building traditional scale neighborhoods.

Not coincidentally, Mehaffy has done a lot of work building livable cities; he was project manager for Orenco Station and education director of the Prince's Foundation. By contrast, Glaeser is an economist who clearly clearly cares more about economic growth than about building livable cities.

Incidentally, we are talking about European-style neighborhoods that are mostly or entirely apartment buildings, not about neighborhoods of rowhouses. I would think that Santana Row is a good example of this style, though I don't know what Michael Mehaffy would think about that.

Daniel Libeskind's proposed towers in Milan are an extreme and somewhat amusing example of what we are talking about. Check out the picture at http://www.independent.co.uk/arts-entertainment/art/news/not-manly-enoug... and think about what these towers would do to the skyline of Milan.

This design is so bad that it would probably make the city less walkable, as towers in a park usually do. It is amazing that Libeskind has a reputation for being avant garde, though he repeats the obvious city planning errors of fifty years ago in this way.

But even if this project were better designed for walkability at ground level, it would do the same esthetic damage to the skyline, in my opinion. And it would have the environmental problems that Mehaffy talks about: building materials with very high levels of embodied energy, high exposure to the elements and inefficient ratio of surface area to volume, which both increase energy used for heating and air conditioning.

Seems to me that they would be better off developing this area in traditional European urban scale, rather than developing highrises here.

Charles Siegel

Skyscrapers often needed for density

I'm not sure that I accept the notion that the benefits of increasing density disappear at 50 people per acre. But using that standard, there are very few neighborhoods in the United States that meet it. 50 people per acre translates to roughly 30,000 people per square mile

For density's benefits to be realized, the density must be achieved over a large enough area to support transit, local stores, services etc. This is very uncommon in the United States. There is Manhattan, a mix of highrises and midrises, parts of San Francisco, center city Philadelphia, and precious few other locations.

To reach this level of neighborhood density of this level, highrises may be necessary. In many cases, it may be easier to strategically insert highrises than to redevelop a massive area with European style 4-6 story buildings. Neighbors may be willing to accept a few highrises more than large scale creation of midrise buildings.

Such large scale projects are usually only feasible on greenfield or near greenfield sites, which do not provide the same ecological benefits in transport modes and infrastructure savings as urban infill. From a market perspective, many developers like highrises precisely because they command high prices per square foot.

Of course, highrises have to be carefully designed so that they do not damage the urban fabric--Vancouver has done an excellent job of that. And highrises are only ecologically valuable when they fit into a matrix of transit and services. Central Miami is a sad example of auto-dominated highrise development without supporting services.

None of this is to deny the value and charm of mid-rise neighborhoods. There are few American urban neighborhoods as lovely as Center City Philadelphia (though even there a few highrises have snuck in, especially around Rittenhouse Square). I'm saying instead that there are other roads to urban density, and highrises are part of some of them.

Skyscrapers and the Real World

I agree with your basic point. If we were starting from scratch, I think that it would be best to build large areas at traditional European density, because it is more livable, has a stronger sense of place and community, and is probably better for the environment than high-rises.

But we are not starting from scratch, and there are *some* places where highrises are now appropriate - most obviously, in downtowns that are already filled with highrises, which exist in almost all American cities. Eg, in downtown San Francisco, highrises fit in with the existing character of the neighborhood, and real-estate values are so high that no infill will be built except highrises.

Note, though, that there are many proposals for highrises in places where these considerations about American cities don't apply - such as Milan and central Paris. And Ed Glaeser explicitly backs those central Paris highrises.

What do you think about those two cases where your points about American cities do not apply? Shouldn't we preserve the character of those cities and build in a more environmentally sound way by building infill in the form of traditional European neighborhoods? There are few major cities in the world that still have this sort of traditional urbanism. Shouldn't we preserve it where it exists?

Those are the big issues where we might agree. Now some points where I have to disagree with you:

"In many cases, it may be easier to strategically insert highrises than to redevelop a massive area with European style 4-6 story buildings. Neighbors may be willing to accept a few highrises more than large scale creation of midrise buildings."

I don't think that is true. Look at our own town of Berkeley. In downtown, there have been lots of 4-6 (and even 9) story buildings developed; there was the usual NIMBY opposition, but not enough to stop them. Then, when the city passed a downtown plan that included highrises, there was such fierce opposition that the city had to back down and propose a modified plan with no heights allowed greater than the existing buildings in downtown.

Highrises are high visibility. When typical Americans think about being able to see a highrise from their house, their reaction is: "this is exactly what I moved to suburbia to get away from."

Most people like European neighborhoods. Americans flock to Europe on vacation just to be able to sit at cafes and enjoy the traditional urbanism. Many would welcome similar projects in their own neighborhoods, as New Urbanists have demonstrated by doing charettes where they design infill projects as traditional urbanism.

City planners like Vancouver, but I do not see Americans flocking there on vacation to sit at cafes and look at the highrises. I haven't seen anyone having the same success in getting neighbors to actively support highrise projects that they have had in getting neighbors to actively support traditional urbanism

"Such large scale projects are usually only feasible on greenfield or near greenfield sites, which do not provide the same ecological benefits in transport modes and infrastructure savings as urban infill."

You can see that this is untrue by getting on BART and traveling south. Oakland Coliseum, Bayfair, and the other stations continuing on both the Dublin and Fremont line have very large areas around them filled with parking lots and other auto-oriented uses. There are also vacant industrial sites between stations.

The same is true in inner suburbs of virtually all American cities. There are large areas devoted to parking and auto-oriented uses that could be developed as traditional urbanism. For more about this, see the CNU web site and Ellen Dunham-Jones' "Retrofitting Suburbia."

"For density's benefits to be realized, the density must be achieved over a large enough area to support transit, local stores, services etc. This is very uncommon in the United States."

They do have to be sizable, but not all that large. Remember that they not only have their own residents as customers. They also have a natural base of customers from the lower density neighborhoods around them.

In many cases, they have problems getting local stores because of retailers' policies, not because of an inadequate customer base.

Eg, downtown Berkeley used to have two department stores, but it has lost them because department stores now want to locate near freeway exits. We have an old hardware store, but we will probably lose it, and newer hardware stores all want to locate near freeway exits.

If we had policies like those in England to prevent freeway-oriented retail from undermining older Main Streets, downtown Berkeley would have the stores needed to serve its residents and nearby residents. (Fortunately, we do have a supermarket.)

There are plenty of opportunities to build European-scale neighborhoods that are the area of downtown Berkeley on infill sites. The European scale would make them much denser than downtown Berkeley. Their residents and surrounding residents should be able to support needed retail - if we have policies to control freeway-oriented retail.

"many developers like highrises precisely because they command high prices per square foot."

That is a good reason for developers to support highrises.

And it is a good reason for people who care about providing affordable housing and promoting a less consumerist way of life to oppose highrises.

Developers will build mid-rises if they are what the zoning allows. I am sure you know that the feasibility study for downtown Berkeley development found that the most economically feasible form of development there is five- and six-story rental housing - because it has lower construction costs and less need for parking than luxury condos.

Charles Siegel

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