skyscraper - Building the Skyline

March 23, 2021 by Jason Barr 2 Comments

Skyscrapers and Housing Affordability: Debunking Misconceptions

Jason M. Barr (@JasonBarrRU) March 23, 2021

Erin go Tweet

On March 9, 2021, Professor Ronan Lyons, an economist at Trinity College Dublin, tweeted about one of my research papers on global tall building construction.^[1] Dr. Lyons has 24,000 followers (two orders of magnitude more than me, but you can follow me on Twitter here). His tweet mentioned the paper’s findings for Ireland. This set off a tweetstorm, with no shortage of opinions—mostly against—about skyscrapers in ancient Dublin town. This post is my response to that tweetstorm.

The Paper

Before I get to Ireland, let us turn to the research that started the whole kerfuffle. The paper is “Cities without Skylines: Worldwide Building-height Gaps, their Determinants, and their Implications” (by Remi Jedwab, Jan Brueckner, and me). The study attempts to understand the causes and consequences of building height restrictions around the world. It is the first to measure global differences and attitudes towards tall buildings.

We estimate the degree to which skyscrapers are “missing” from every country due to stringent building height regulations. To do this, we come up with a prediction of how much building height a nation “should have” if its real estate market was relatively open, and then compare this to the actual total building height. We call the difference the “building-height gap.” Higher gaps mean more “missing” buildings, given the income levels.

No Free Lunch from the Fear of Heights

The paper shows that the building-height gap is highest for richer countries and is driven mainly by stringency in the housing sector. The evidence also suggests that wealthier countries with higher gaps have older cities and are more interested in preserving their national heritage. Just as importantly, we also find that the gaps are positively related to sprawl, air pollution, and higher housing prices. In short, we see that countries with more restrictive building height regulations are imposing a degree of economic harm on their residents. One might say that there is no free lunch from the fear of heights.

Irish Developer Johnny Ronan Seeks to Building Ireland’s First Skyscraper. The 45-storey residential tower in the Dublin docklands would be the tallest building in the country Source: *The Times*.

The Tweebate

When we crunched the numbers and came up with the country that had the largest height gap per million urban residents, it turned out to be Ireland, which has no skyscrapers (100 meters or taller), though one is seemingly in the works. Across the world, there is a strong correlation between national income and building heights. Richer countries build taller, on average, because they are more urbanized. However, Ireland—and Dublin, in particular—is both relatively wealthy and has robust business services and financial sectors, which tend to promote tall building construction for both office and residential purposes.^[2]

Professor Ronan argued that Dublin should not be so afraid of heights if it is genuinely concerned with housing affordability. Building upper-class high-rises can help, albeit in a small way, to reduce housing prices more broadly. This comment set off a flurry of responses about tall buildings’ impacts on affordability and urban form. Common among them were the typical tropes about skyscrapers and cities. I want to take this chance to rebut some common misconceptions. It is better to do it in long-form than on Twitter with endless 280-character back-and-forth jabs—peppered with personal attacks—which I find emotionally stressful and ultimately a poor vehicle for fruitful discussion.

Heights versus GDP. This graphs shows a country’s total tall-building height per thousand urban residents versus its gross domestic product (on log scales). Given Ireland’s relatively large GDP, it has fewer tall buildings than expected. The line gives the average tall-building height intensity for each GDP level. Source: Jedwab, Barr and Brueckner (2020).

Revisiting the Myths

Myth #1: “Building up is pricing up”

Because skyscrapers are expensive to build and operate, people believe that, by their very nature, they increase the price of housing, or as one Tweeter put it, “building up is pricing up.” But the opposite is true. The idea that building up is pricing up confuses correlation with causation.

Skyscrapers are a response to high land values. When land is expensive, it signals that the demand for that location is high and that people are willing to pay more to be there. As a result, developers respond to the demand by building tall. A high-rise building in a low-density suburb makes no economic sense. The prices of land do not justify the expense of going tall. This is why the vast majority of tall buildings around the world are in central metropolitan areas.

Anytime a building comes online, it slightly increases the supply, which reduces prices. This impact is often hidden in large cities with relatively little new construction because the demand side–which pumps prices up–swamps the supply side. However, if you dumped many high-price units on the market at the same time, it would push prices downward. Would it reduce prices all around the city? No, but it would certainly help in, say, a one-kilometer radius around the new construction.

Myth #2: “Skyscrapers cause gentrification”

Gentrification is caused by high demand relative to low supply. When a new high-rise goes up, it has two effects. First is the supply-side effect, which reduces neighborhood prices, ever so slightly. However, because the tall building now allows for a denser neighborhood, it increases the demand for neighborhood services, such as coffee shops and pubs, which can draw more people in, further raising real estate prices.

But in a smooth-functioning market, rising prices due to increased amenities will be met with more housing, which would reduce the number of people who feel pushed out by the neighborhood’s increased attractiveness. Gentrification is caused by frictions or barriers to new construction, including tight building regulations and high construction costs. These barriers generate “fixed-pie” neighborhoods: those who can afford it can get a slice of the pie. The rest need to go elsewhere. More housing increases the size of the pie.

Myth #3: “Hong Kong has lots of skyscrapers. Hong Kong is expensive. Therefore, skyscrapers must make Hong Kong expensive.”

While I will have more to say about Hong Kong in a future post, the opposite of this idea is true. Hong Kong is expensive not because of its skyscrapers, but despite them. Hong Kong’s problem is due to its unique land and housing markets.

The first is land scarcity. A large swath of the city has mountainous, steep terrain and is unsuitable for building. More importantly, the government owns all the land and doles it out in varying amounts. While the precise nexus between land supply and housing supply remains debatable, developers’ ability to quickly adjust the housing stock based on demand is highly constrained.

Additionally, Hong Kong has a dual housing market, which tends to lower affordability. 45% of housing units are owned by the government. The rest is free market. This two-tiered system encourages high-prices in the free one because no one leaves the cheap public housing (once you apply, the average waiting time is 5.7 years to get a public housing apartment), forcing the rest to seek out scarce market-rate shelter.

When big cities have two-tiered systems, the lower and middle-class residents who cannot get into the subsidized units are the ones who invariably suffer. Because new construction in the unregulated sector is limited, it will mostly be dedicated to high-priced housing accessible to the upper classes, leaving the rest to bear the brunt of the shortages.

Myth # 4: “Developers want to build skyscrapers everywhere.”

Skyscraper construction is only profitable in locations where land values and real estate prices are high enough to incentivize construction. Because of their size and their occupants—upper-income folks—they tend to be viewed as agents of income inequality and gentrification.

But in any city with many building restrictions, developers find a way to provide new housing where there are the greatest profits—in the city center. There are many low-rise, middle-income neighborhoods throughout a city where new construction at slightly higher densities—for example, replacing one-family homes with four-story apartment buildings—could be profitable. But residents do not want new construction in their neighborhoods.

They shout, “Not in my backyard!” and then complain when skyscraper developers build high-rises in other people’s backyards. If you limit construction throughout the city, skyscrapers appear in the central pockets where developers can “squeeze” them in and make money satisfying the demand. They cannot satisfy the demand elsewhere because restrictive zoning or building regulations prohibit them from doing so.

Myth #5: “Goldilocks density should be imposed throughout the city”

Jane Jacob’s 1961 classic book, The Death and Life of Great American Cities, sparked a debate about the ideal urban neighborhood. Jacobs wrote about her Greenwich Village street in virtually utopian terms. Recent research has confirmed that dense, low-rise mixed-use neighborhoods have all sorts of desirable characteristics: They have a diversity of people and amenities, their carbon footprints are lower, and they “feel” warm and cozy. These historic, pre-automobile neighborhoods represent in the minds of many a Goldilocks neighborhood—not too hot, not too cold, but just right.

The Goldilocks supporters rail against the “plutocrat” developers destroying neighborhoods with their elitist skyscrapers. The policy implication of this view boils down to “Not in my backyard!”—preserve the historical communities in amber to keep them precisely as Jane Jacobs described them six decades ago and ban tall buildings in urban centers. In essence, take the Paris route to urban land use policy: Forbid anything that does not conform to their notion of the perfect city.

In the Balance

Do not get me wrong: I love Greenwich Village and old New York, and historical preservation is vital! But we must also recognize the costs of these positions—historic preservation limits new construction, which raises prices. Additionally, the notion that there is one ideal density that should be mandated by law is absurd.

Skyscrapers in the center represent the demand to live in dense central areas, and if people demand more density, then tall buildings fulfill a need.^[3] Areas farther out from the center should be leafier and less dense—that is the benefit of living farther away. True Goldilocks density is a moving target, and land-use policies should reflect this by being flexible.

Having said this, if New Yorkers, like Parisians, want to “vote” to preserve their city as it existed a century ago, they should be clear that they prioritize aesthetics and historic preservation over affordability and that the closed city is to be only for the rich who can buy million-dollar studio apartments in low-rise Greenwich Village and let everyone else fend for themselves.

**Myth #6: “Skyscrapers destroy the ‘*human scale***‘”

The perception is that tall buildings next to low-rise buildings or tall tower-in-the-park style high-rises destroy the “feel” of the city. This is an issue, aside from the economics of housing supply, that merits serious discussion. The fundamental question we face in the 21^st century is how to create cities that are both affordable and enhance life satisfaction.

Detractors of tall buildings say that towers make the city “feel cold” and dampen the vitality of the streets. True, not all tall buildings fit within the urban fabric, and glass boxes can be alienating to passersby, but two important points need to be made.

First is that human scale and quality of life are more directly harmed by dependency on automobiles. Dense urban neighborhoods are inherently more vibrant than those with, say, sprawling suburban tracts and strip malls, or big cities that build six-lane highways directly through the center. If the aim is to create more livable cities, we should focus on creating critical densities that promote diverse populations, various uses, and more mobility.

Automobiles are a bad way to move people. They take up a lot of urban land for roads, parking and storage, and they are too easily subject to congestion. Four automobiles will, optimistically, carry eight commuters during rush hour. For the same length, a bus or streetcar can carry perhaps 50 or more people. Cars also promote sprawled-out, low-rise living.

If cities are really concerned about the quality of life, the focus should be on improving non-car-based mobility among urban residents first and then allowing neighborhoods to densify up based on where people want to be. Increasing density along subway lines and commuter rails is a great way to start.

Urban Umami

Secondly, as I have argued elsewhere, if we want to improve the feel of cities, we have at our disposal new methods and technologies that allow us to better understand human preferences and the psychology of streetscapes. Once we know this, municipal regulations can incentivize good urban design—to make new construction feel less oppressive in people’s minds, and blend better with the historical urban fabric.

Imposing low-rise density in the city center is inherently exclusionary since it generates housing shortages in the name of “human scale.” We all want to live in a city that feels nice, but only the rich can build cities that uphold their notions of ideal beauty but ignore economic realities.

The Manhattan Skyline from Central Park. Photo by Jason M. Barr.

Guiding Principles

While I will have more to say in future posts about urban policies that get us to cities that are both affordable and high-quality, we need to begin by clearing away the misconceptions about tall buildings. So, at the risk of repeating myself, let me summarize.

Supply and Demand

First, real estate markets operate like all markets—according to the laws of supply and demand. The more these laws are subverted, the more they wind up harming residents, usually in the form of unaffordable housing due to excessive building regulations and other frictions. All cities need to find the right balance between regulation and growth, and the current global affordability problem is driven, in large part, by the desire to guard and preserve the present and past city against fears of the future city.

Tall Buildings are Efficient

Second, skyscrapers are built in central areas where demand for housing is high. As such, they represent an efficient use of land. The fact that skyscrapers are more visible and tend to be for upper-income residents should not distract us from the fact that more housing is needed at all income brackets and at locations where cities experience an extreme “shortage” of housing.

A look at New York, for example, shows that about 50% of the entire residential land area is currently used for one- and two-family homes. This is inefficient. We should spend less time worrying about Manhattan skyscrapers and more time getting neighborhoods with four houses per acre (10 houses per hectare) to add more units.

Skyscrapers do not Belong Everywhere

Third, skyscrapers do not belong everywhere. They are not economically rational or practical outside central areas. In suburban districts, densification should entail converting smaller buildings to those that are a bit denser. People should have the right to convert one-family housing to two- or three-family housing or convert garages to rentable apartments, for example.^[4]

More housing, regardless of the occupants’ income, can help reduce the price of housing. The key is that for a city to remain affordable, it must increase its supply faster than prices rise. When this happens, housing prices moderate. Tall buildings can help, though by themselves, they are not sufficient.

Missing the Forest for the Trees

Fourth, getting angry about one high-profile project each time it crops up is missing the forest for the trees. Focusing on one building or neighborhood at a time is not only inefficient but harmful for residents more broadly. Policies need to be citywide, and they must ensure that every neighborhood gets its fair share of housing based on the demand for those neighborhoods.

Livable Cities

Fifth, livable cities must begin with sound economics. If we want livable cities, we should abide by three principles.

Let density naturally arise where people want to be and let mixed-uses and diversity emerge along with it. High-rises should go where high-rises should go, and low-rises should go where low-rises should go.
Excessive automobile dependency subverts quality of life more than tall buildings. Simply creating central-city congestion pricing is not the answer. Any transportation system needs to maximize mobility and access, including pedestrian routes and bicycle usage.
Modern social science methods can now be used to better understand what kinds of building and street designs make people feel more at ease and encourage people to come out onto the streets. But implementing good design practices while ignoring the economic and transportation issues is insufficient to produce better cities. If we limit new construction, we wind up getting better-designed cities for rich people.

The Future City

All cities—ancient and new alike—must find the right balance between preserving the past and promoting the future. New York is New York and Dublin is Dublin because, historically speaking, these cities had the flexibility to add housing as the demand arose. Of course, the process was messy and led to a whole suite of building regulations to slow down cities’ ability to change. That is where we are today; the result is an affordability problem. We forget that the historical city was a much more dynamic place, and this dynamism created the magical metropolises we have today. We have nothing to fear but the fear of heights.

Thanks to Maria Thompson for her help with proofreading editing.

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[1] In the interest of full disclosure, Professor Lyons and I are research collaborators, though he did not work on the research paper discussed in this post. His Tweet was not discussed with me before he posted it. Professor Ronan has no relationship with Johnny Ronan, the developer proposing to build a 45-story tower in Dublin.

[2] Ireland has 4.9 million people, and the Dublin metro area has 1.23 million—nearly 20% of the population. Relative to other European nations, its urbanization rate of 63.41% is relatively low. But given its high income and Dublin’s successful economy, it under-produces tall buildings relative to similar countries.

[3] I also want to be clear that luxury high-rises should not be used by shell corporations to hide or launder money. I have written on this debate here and some policies that can address the negative externalities that might arise from billionaire condo skyscrapers.

[4] When I was in college, my friends and I rented the bottom floor of a large Victorian house near campus. Legend had it that was occupied by Vladimir Nabokov when he was teaching at Cornell. The top floor was converted to a separate two-bedroom apartment. All told, that house was able to comfortably accommodate at least six college students (and their dating partners). Today, such a conversion would be illegal in many cities and would mean that a small household living there would need to keep otherwise usable space unoccupied because the law requires it.

January 20, 2021 by Jason Barr 1 Comment

Clouds in Your Coffee? Skyscrapers and their Symbolic Heights

Jason M. Barr January 20, 2021

You’re So Vain?

On January 4, 2010, the Burj Khalifa officially opened its doors. At 828 meters (2,717 feet) it became the world’s tallest building by a long shot. It overtook the previously tallest building, the Taipei 101, by 302 meters (991 feet). The only rub: Much of Burj is empty space—the top third is a 243-meter (797-foot) spire—where no human will likely ever work or live.

The difference between the actual or architectural height (excluding TV and radio antennae) and the highest occupied floor is what the Council on Tall Buildings and Urban Habitat (CTBUH) has dubbed “Vanity Height.” They originally coined the term, with tongue in cheek, because some developers—presumably—have added a decorative element simply so they can brag about having a taller building. For the CTBUH, the de facto arbiter of official building heights, these elements create a conundrum.

The most famous recent examples of Vanity Height are the Petronas Towers (1998) and One World Trade Center (2014). When completed, the Petronas Towers took over the title as the world’s tallest building (until 2004) because of its spire. The highest occupied floor remains well-below the previous record holder’s top floor, the Willis (Sears) Tower (1974). To many, it seemed that to beat the record, you simply build a tall skyscraper, attach a glorified pole, and declare victory.

Similarly, One World Trade Center, in New York, is only the tallest building in the Western Hemisphere because of its 154-meter (505-foot) spire, which looks more like an antenna than an artistic statement. Its sole purpose, it appears, is to allow the skyscraper to rise 10 1,776 feet (541 meters), as a symbolic gesture to the birth (and hopefully continuance) of American Democracy.

Space Wasters?

In 2013, the CTUBH published an article discussing so-called Vanity Height. They showed that among a crop of 200-meter or taller buildings, several notable examples had spires or other architectural elements of at least 95 meters (312 feet), comprising 25% or more of their respective total heights. The article tickled the funny bone of the press, who went on a reporting rampage, producing such splashy headlines as, “Space-wasting ‘vanity’ skyscrapers revealed,” and “44 of the world’s 72 tallest buildings are cheating.”

Assumptions

While the 2013 article was meant as a jocular jab at some developers, the phrase has remained in the public sphere because it feeds the belief that skyscraper builders are only concerned about self-glorification and are unconcerned about other mundane things like profitability or urban well-being. The phrase “Vanity Height” implies that all structures with large vertical voids are—by definition—ego-borne. But this belief obscures other reasons for what is happening up top. The drivers and impacts of this extra height are more complicated.

Another implicit assumption is that skyscrapers are getting “vanier”—that builders are adding more of it now than in the past. The phrase fuels the idea that developers in the 21^st century are engaged in an arms race to claim the prize. This suggests a degree of dissipative or wasteful competition—that by adding height to stand out, developers are spending resources to satisfy themselves, with no larger benefit to society. To what extent are these assumptions true? The answers will be revealed below when we look at the data.

Vanity Heights? Despite the controversy, the degree of “space-wasting” height among the world’s tallest buildings varies widely. The Twin Towers and Willis (Sears) Tower have virtually none, while more recent structures add a varied amount (ignoring antennae). From Left: Burj Khalifa (2010), Petronas Towers (1998), Taipei 101 (2004), Willis (Sears) Tower (1974), Twin Towers (1972/3). Note that the buildings are not to relative scale.

From “Vanity Height” to “Symbolic Height”

Tall buildings serve many purposes beyond providing space for people to work, live, or play. They also convey information: Big corporations like to be in iconic buildings because they signal something about their business, such as their profitability or trustworthiness. Corporate headquarters are part of the larger need for branding because branding gives a certain level of assurance about what consumers get when they buy a company’s products. More broadly, companies that have national or international ambitions find they need to be in skyscrapers to signal their ability to compete in the global marketplace.

Cities like to have iconic structures because they increase tourism, foreign direct investment, and advertise that the city is a dynamic urban center. Architects, when designing tall buildings, also have multiple goals. They want to not only deliver an iconic structure to their clients but also seek to make their buildings aesthetically pleasing and meaningful. To architects, “Vanity Height” is often shorthand for the design up high.

I asked architect Ro Shroff, of 3MIX, who is involved in several tall building designs around the world, his thoughts:

I generally concur with the notion of Vanity Height, and it has almost become a de rigueur methodology for most architects, to “enhance” the proportions and appearance of the tower, and create some identifiable iconography to differentiate from other skyline cacophonies. This is accomplished either by extending the façade as a screen to hide the rooftop equipment or by creating unoccupiable voids, vertical spires, spiraling crowns or glowing lanterns, not too dissimilar from the design intents of the Empire State and Chrysler Towers in the 1930s.

Then there are developers who may want to have icons for their personal satisfaction or bragging rights. But this leads to an important question: Where do beauty and iconicity end and vanity begin? This is inherently unanswerable. Shroff adds, “Hopefully and presumably, such vanity exercises in ‘irrational exuberance’ by the architects or developers are also countered with fiscal responsibility, maintenance economics, and other checks and balances.”

The Information

The bottom line, however: We cannot say much about so-called Vanity Height by looking at a few buildings. We can cherry-pick and shout-out the ones that appear most egregious. But, as I show below, the data strongly support that relatively few buildings are as bad as we think.

This leads me to propose a new name for this type of height: Rather than Vanity Height, we should call it Symbolic Height, because it is height added to convey information of some kind.[1] This information can be literal, like broadcasting the name or logo of a corporation, or abstract, such as an aesthetic design or sculptural elements.

Early Examples of Symbolic Height in New York City. From Left to Right: World (Pulitzer) Building (1890) with decorative dome; Tribune Building (1875) with decorative tower; Singer Building (1908) with occupied tower; Empire State Building (1931) with mooring mast/spire. Note: Buildings not to scale.

A Brief History of Symbolic Height

Symbolic Height has a long history and is older than the skyscraper itself. A review of this history demonstrates the multiple purposes that tall structures serve, the different types of information that they broadcast, and the benefits of the voids up high.

We can think of gothic church spires or old city hall clock towers. Sure, their heights were meant to announce the power of the institutions that created them, but they also served other purposes, especially related to telling time—church bells and clocks to telegraph the hour of the day. They also provided locational beacons—in a low-rise city, people could head for the center by moving toward the structure rising in the skyline.

Then there are towers, arches, and obelisks, built with no other purpose in mind than as symbols (with the occasional observation deck thrown it). Despite their “useless” objectives, do we complain that the Eiffel Tower is too tall or that the Washington Monument is a waste of resources?

When the building technology to go tall was perfected, developers—be they corporations or individuals—realized they could add extra heights to convey information about the occupants or builders. The first record-breaking buildings in New York, such as the Tribune Building (1875) or World (Pulitzer) Building (1890) added decorative towers or domes to raise themselves above the fray and to express the power of their business or industry.

Early developers also added occupied towers. Both the Singer Building (1908) and Woolworth Building (1913) are large, bulky office building with extruded towers, which also play the role of Symbolic Height, though, in these cases, they also provided office space. It also shows that not all Symbolic Height is empty space or decorative spires.

And yes, developer and ego-based competition has driven buildings to be taller than they would otherwise be. The developers of the Empire State Building (1931) added a 61-meter (200-foot ) dirigible mooring mast to lock in the world record, while Walter Chrysler added the 56-meter (185-foot) stainless steel spire—“the Vertex”—to beat out the Bank of Manhattan Building (1930) at 40 Wall Street. However, without this competition—this “Vanity Height”—the city would feel a little emptier.

There are examples around the world of practical uses for the voids up top. The Ping An Tower, in Shenzhen, contains a mass tuned damper that helps stabilize the building against wind forces. In the observation deck of the Shard, one can look up into the “Vanity Height,” hovering above; the experience helps enhance the pleasure when viewing the London skyline.

The Opposite is Also True

Not every record breaker or supertall has Symbolic Height. Both the Twin Towers (1972/3) in New York and the Willis (Sears) Tower (1974) have near-zero additional space above the top floor. Architectural modernism after World War II was a movement away from overt expressions of decorative height. The idea was that record breakers speak their intentions simply by being tall towers. Today, the view of “Billionaires Row” from Central Park shows wide architectural variety on top. 432 Park Avenue—like the former Twin Towers—just stops, with no decorative elements. A few blocks away, the rising Steinway Tower has a tapering, almost two-dimensional, 90-meter (295-foot) crown. Vanity or art? Perhaps both.

Symbolic Height: A Look at the Data

Despite some interesting examples here and there, we cannot say much about Symbolic Height, on average, because no one has analyzed more than a handful of buildings. To this end, using the CTBUH database of tall buildings, I have performed a statistical analysis to look at the patterns of Symbolic Height for about 2,000 skyscrapers worldwide.

The goal is to answer a set of related questions: Is Symbolic Height—the difference between the architectural height and the height of the highest occupied floor—a systematic part of the tall building universe? What has been happening to Symbolic Heights, on average, over time? Has it been rising, as is commonly assumed? Does the data support the idea of dissipative or wasteful competition among developers? And lastly, are China and the United Arab Emirates (UAE) the worst offenders, as people commonly assumes? (Data sources and statistical results are here.)

Symbolic Height Around the World

The answer to the first question is “no.” The average Symbolic Height, as a fraction or percent of total height, for buildings around the world of at least 100 meters is about 10% (with a median of 8%). In other words, on average, Symbolic Height represents only 10% of the total structure’s height, which suggests it typically plays a very small role. For supertall skyscrapers of 300 meters (984 feet) or taller, that average is still quite low at 12% (median of 9.7%).

This is not to imply that all tall buildings have a Symbolic Height of only 10%. There is a degree of variation—mostly on the low end. 75% of 100-meter or taller buildings in the database have a Symbolic Height of 12.5% or less. Only 5% have a Symbolic Height above 22%. For those at or above 300 meters, the numbers are similar: 75% of these buildings have a Symbolic Height of 18% or lower. Only 5% have 28% or higher.

Variations in Symbolic Height. Left: Relative frequency histograms (%). The blue line gives the distributions for Symbolic Height for 100 m+ buildings in the sample. The orange line gives the distributions for 300 m+ buildings. For example, about 18% of 100 m+ buildings have Symbolic Height around 8%. Right: Cumulative relative frequency histograms. The blue line gives the percent frequency of Symbolic Height at or less than each value for 100 m+ buildings. The orange line is for 300 m+ buildings. For example, about 80% of 100 m+ skyscrapers have Symbolic Height less than or equal to about 13% Source: here.

Symbolic Height Over Time

What about over time? Is Symbolic Height growing? Again, the answer is “no.” Using this data, I have created a Symbolic Height Index (analysis here), which gives the average Symbolic Height around the world each year, relative to the long run global average of 10%, after controlling for building location and use. The results suggest, first, that is no long run trend, but rather is cyclical. The Index peaked in the 1997 (a year when no new world record breakers were built), before Asian countries dove into the skyscraper game. As places like China and the UAE ratcheted up the tall building construction in the 2000s, the Index moved up until 2006 (before Global Financial Crisis) and has been falling ever since.

The Index also reveals relatively muted movements. Even in robust times, when more developers were adding extra height, the highest amount above the average was 7 percentage points. In other words, the data suggest that Symbolic Height is based on fashion or tastes, rather than developers need to systematically outdo each other. The findings also suggest that “irrational exuberance” is punished in the long run.

Global Symbolic Height Index. This index gives the percent of Symbolic Height relative to the long run average (10%) for each year from 1968-2018. Note this index is an moving average (3 years) from 1966 to 2018, with 1982=10 (the long run average). Source: here.

Symbolic Height by Country

Which countries are the most egregious on average? The results of the statistical analysis are surprising. Among the 64 countries that have built at least one skyscraper since 1966, the top three are Ethiopia, Kenya, and New Zealand, with average Symbolic Heights of at least 25%. The UAE, China, and the United States are in the middle of the pack.

Just focusing on countries that have built at least ten skyscrapers, the UAE and China rise in the rankings. But their averages are still not that far above the global average of 10%. In short, when it comes to Symbolic Height, these countries about average. Among the public perception, China and the UAE appear to be “bad” because there are a handful of notable extreme cases. However, by focusing on those, we lose the skyline for the skyscrapers.

Symbolic Height by Country. Left: Rankings and average Symbolic Height for selected countries based on 64 countries with at least one skyscraper. Right: Rankings and averages for selected countries based on 27 countries that have at least ten skyscrapers. Source: here.

Variety is the Spice of Life

Given there is a certain cache to having a nominally taller building, the “stick-a-pole-on-it-and-declare-victory” type skyscraper is not likely to go away anytime soon. But a review of the broader evidence suggests that these types of buildings are the exception rather than the norm. There’s also little evidence that developers are engaged in a dissipative battle royale to beat each other for the title. So what if there are a few too-tall buildings out there? The variety alone makes it worth the cost.

Thanks to Maria Thompson for editorial assistance.

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[1] Note that in my book, Building the Skyline (2016), and a previous blog post, I defined Symbolic Height in a slightly different manner. There, Symbolic Height was the difference between the actual or architectural height and the profit maximizing or economic height based on revenues and construction costs. Thus, Symbolic Height can include extra floors above the profit amazing height in addition to decorative elements or spires. Given that the two definitions of Symbolic Height are likely to be fairly close, on average, it can be a reasonable substitution for the definition of Vanity Height.

October 23, 2019 by Jason Barr Leave a Comment

The Technology of Tall (Part III): Getting to the Core

Jason M. Barr October 23, 2019

Note this is Part III of an on-going series on the evolution of skyscraper technology. The rest of the series can be found here.

The Too-Tall Debate

A common assumption about many of the world’s tallest buildings is that, from an economic point of view, they are too tall. Their heights, it is argued, don’t produce an income that justifies their expense. They are monuments, not moneymakers. This was a common refrain in the early 20^th century when planners and reformers were attempting to limit building heights in large cities across the U.S. The Founding Fathers of modern zoning—the members of the New York City Heights of Buildings Commission—were convinced that skyscrapers were bad economics. In their 1913 report they wrote:

Few skyscrapers pay large net returns. Most of them pay only moderate returns. The cost per cubic foot of tall buildings is greater than that for low buildings. The exact difference can only be approximated because there are so many factors which affect the problem. However, the very tall buildings demand many things out of proportion to their increased bulk. All piping has to be made disproportionately heavier; special pumps and relays of tanks have to be provided, foundations often call for special construction, wind-bracing assumes an important place, long-run elevators are more costly than short-run elevators, the extra space taken up by the express run of the elevators is an additional cost. Thus in the aggregate the total cost per cubic foot of a very tall building may be 60 to 75 cents per cubic foot where a low building of the same class would cost only 40 to 50 cents per cubic foot.

The Response

By focusing only on their expenses, they naturally assumed that there’s too many “extras” to make a skyscraper a competitive investment. In 1930, the economist and architect, W. C. Clark and J. L. Kingston, respectively, in their book, The Skyscraper: A Study in the Economic Height of Modern Office Buildings offered a hearty rebuttal to the complaint:

This is the contention that the tall building is an economic fallacy,—that even from the private owner’s point of view it does not “pay” and therefore should not be permitted. Now the solicitude of the critic for the poor building owner who foolishly insists on putting money into unprofitable investments is somewhat amusing and hardly consistent with the claim that the latter is a robber of values that rightfully belongs to others, that he who is allowed to build a tall building is given an economic advantage which should be compensated for by heavier taxation, etc. However, if we are willing to overlook such patent inconsistencies, we will recognize in this “economic fallacy” argument an ingenious flank attack upon the position of the skyscraper enthusiast.

And even today the complaint is frequently heard that buildings like the Burj Khalifa are extravagant because they will, allegedly, never turn a profit. And while this might be true from time to time, there is little evidence to show that skyscrapers are systematically bad investments. Rather, around the world, on average, developers appear quite rational in their decision making.

The Efficiency Problem

Of the many arguments that detractors put forth against skyscrapers is that they are an inefficient building type, since up to 30 to 40% of the total floor area—which is used for elevators, stairwells, and plant and equipment—generates no income. A 10-story office building may be able to rent 85% of its area, while for a 50-story tower, that number might fall to 70%. If you telescope only on the efficiency ratio—rentable area divided by total building area—you will naturally conclude that there’s too much “wasted space” in the taller building. But from the point of view of the developer, the aim is to get the most profit from a lot. This requires the balancing of a trade-off between the costs and benefits of going tall. Thus, efficiency ratios are only one side of the equation.

Going to taller is beneficial in that it adds extra floors to the structure which have both user and market values. The occupants like to be higher up because they get better views and other economic and social perks, and they are willing to pay a premium to be in the sky. However, adding extra floors also means additional costs. First is that the central core needs to be expanded to provide for more elevators. This expansion creates two types of problems. First, these additional elevators are expensive—they are costly to purchase and operate, requiring a lot of energy. Second, the extra shaft space for the elevators means less rentable space on the lower floors. Third, as mentioned above, going taller requires extra materials to make the building more stable—extra steel or concrete for wind bracing, and thicker columns at the base.

Optimal Height

But from the point of the view of the developer the question becomes: do the costs of going taller get “paid for” by the income generated by more floors at the top of a taller building? That is, when does height win over efficiency? This answer to this “optimal height” question is determined, of course, by many things, such as the size of the lot, local building regulations, and the state of the economy. But most importantly, in central city locations were rents or prices are high, going taller is beneficial because of the height premium on the higher floors and the demand to be at these central locations.

Left: Bank of China Tower (70 floors, 1990) , Hong Kong. Efficiency Rate: 68.64%. Middle: 900 North Michigan (67 floors, 1988). Efficiency Rate: 78.64%. Right: Süzer Plaza (34 floors, 1998), Istanbul. Efficiency Rate: 71.43%.

Core Tech 2.0

And, developers are not passive actors–simply choosing between height or efficiency. Rather, they are actively engaged in playing the game of “beat the core,” by engaging in a kind of space race to increase the efficiency of new buildings. Architects, engineers, and building suppliers work with developers to figure out ways to either reduce the number of elevators or to arrange the core within the structure to get more usable space. So how has core technology advanced over the years?

Elevatoring Improvements

In another post, I discussed the evolution of elevator technology from the point of view of vertical transportation—the eternal battle to get occupants to their destinations in the quickest and most stress-free manner as possible. Developers have an incentive to move people faster because they can likely charge higher rents per square foot in buildings with better accessibility. And, if elevators are faster, they can allow for a taller building.

But elevators come with many costs. First they produce a large electric bill, that can account for 2-10% of a building’s total energy costs. They also require frequent maintenance and supervision. And, historically, elevators have had to be accompanied by large machine rooms for the motors. In recent years, many technological advances have made it possible to reduce the number of elevators. First, and arguably most important, has been the implementation of software and computing technology, known as Destination Dispatching Systems, that can allocate elevators in a manner the moves the most amount of people in the shortest time possible. This is also combined with zoning, where certain cabs only stop on specific floors. And elevators only for the highest floors are reached through sky lobbies. These innovations combined with using two elevators in the same shaft—double deckers—have made each car more productive.

But Wait, There’s More!

A host of other technologies are also making vertical movement less costly to provide. This includes machine-room-less technology that puts the motors and other equipment directly in the hoistway, obviating the need for a separate room. Additionally, traditional elevators systems used a gearbox to turn a pulley over which the rope passes to move the cab up or down. Today’s elevators can be run gearless, reducing energy usage by up to 25%. Finally, like breaking in automobiles, elevator breaking produces heat, which is normally dissipated through a heat resister. Today, regenerative technology can harness the heat and reuse it to power the elevator, reducing total energy use. In short, gearless, machine-room-less elevator systems with regenerative drives have reduced total energy usage by about 65% as compared to the older technologies (see Figure 3 in Al-Kodmany, 2015).

Mixed Uses

Another strategy to reducing the core is to construct a mixed-used building. In many cities where tourism and residential demand are growing faster than office demand, a mixed-use structure is more profitable on several fronts. First, it better matches the supply with need, while also diversifying the occupant mix, thus generating more revenues. And second, it allows for a reduction of the core. The reason is that a single-use office building has peak loads—seemingly everyone shows up to work between 8:00am and 8:30am, and everyone wants to leave between 5:30pm and 6:00pm. These peak usages require a large number of elevators on hand, despite the fact that for much of the rest of the day, many of the elevators sit idle.

A mixed-use building, with say offices on the lower floors, a hotel above those, and residential apartments on top, can generate a much smoother flow of people into and out of the elevators. The office workers will want the elevators during rush hours, while the tourists and residents will likely use them during the rest of the day. Thus, fewer elevators are needed to accommodate the traffic and this can further help reduce the number of shafts.

Building Cores for Nine Asian Skyscrapers. Source: Ho (2007).

Core Placement

Traditionally, the core has been placed in the center of the building. But various innovations in building technology and design have “liberated” the core from the center. This means that today, its location can be placed in different parts of the building and which can potentially increase efficiency and improve building quality. For example, cores can be moved to the outside perimeter of the building, and allow for greater unobstructed floor spaces, as well as more flexible layouts. Core placement can also reduce energy usage. In hot and tropical climates, a core on the perimeter can shade the occupied spaces. In the cases of the superslim, Manhattan luxury towers on “Billionaire’s Row,” developers can strategically move the core to one side of the building, where the views are less valuable. For example, by placing the core toward the west or south, more units can have views of Central Park to the north.

Examples of Offset and Non-centered Cores. Source: Oldfield and Doherty (2019).

The Evidence

As I have discussed, developers are eager to increase the income-generating areas of their buildings. But the question remains: are these technological innovations reducing the number of elevators and increasing building efficiency rates over time? To this end, I have constructed a data set to see if there’s evidence that buildings are, in fact, becoming more efficient over time. (More information is available here.) The data contains the efficiency rates of 66 office or mixed-use buildings completed since 1955, along with information about usage, heights, gross floor areas, and the cities in which they reside.

The results of the statistical (regression) analysis support the hypothesis that buildings are getting more efficient. In fact, the analysis suggests that, on average, efficiency rates have improved by about 0.1 percentage points per year, or by about 5 percentage points in the last 50 years. Note that in the sample, efficiency rates range from 60% to 86.4%, with a mean of 76.8%. Thus, on average, a building with a 75% rate 50 years ago would likely be at 80% today. If the building has one million square feet of total floor area (92,903 square meters), that translates into 50,000 more “billable” square feet (4,645 square meters).

The Future?

Unless Star Trek transporter technology is invented, the core can never be eliminated. There will always be a need for elevators, stairwells and other service areas. And the core can play an important structural role, often acting as building’s spine of sorts. But perhaps the future is not so much about shrinking the core as it is bending it. Someday the ropeless maglev elevator may make getting through a building something like being in a Pac-man video game–moving horizontally as well as vertically. In the next post, we take up how the skyscraper battles against the elements of earth, wind and fire.

Continue reading. The rest of the series on the technology of tall can be found here.

September 24, 2019 by Jason Barr 3 Comments

The Technology of Tall (Part II): The Need for Speed

Jason M. Barr September 24, 2019

Note this is Part II of an on-going series on the evolution of skyscraper technology. The rest of the series can be found here.

The Chicken or the Egg?

What came first: building height or elevator speed? The history of skyscrapers brings us to a kind of chicken-and-egg conundrum. Does the drive to build tall come first and then fast elevators come next? Or do rapid elevators show what’s possible and then developers exploit them to go taller? While I don’t think there’s any way to answer this question, we can look at the history of the elevator to get a sense how this co-dependency has evolved.

We can say for sure that there is a symbiotic relationship between building height and elevator speed, and together they have enabled cities to grow upwards and hold more people and businesses. Ironically, elevator speed history emerges out of a strange paradox. People are willing to spend an hour or more commuting each day—idling in traffic or dawdling on trains—but when they get to a building, they expect to get from the ground floor to their destination in less than two minutes. It’s the quest for convenience, as much as speed, that has driven the technology forward.

The Birth of Vertical Transportation

Modern elevators are products of the Industrial Revolution, and were first installed in factories, mines, and warehouses. By the 1830s, for example, they were in numerous British textile mills. By the 1840s they were used for passengers. Bunker Hill Monument in Boston, erected in 1842, had a steam-powered lift to take visitors to an observation deck. Wealthy people started putting them into their homes in the 1850s. The first commercial elevators seems to have been installed in New York City before the Civil War. The two earliest examples are the 5-story Haughwout Building (1857) in Soho, and the Fifth Avenue Hotel (1859) at Madison Square Park. Over the ensuing decades, inventors and entrepreneurs continued to advance the art and science of elevatoring to make them faster and safer.

The Safety Break?

The conventional story regarding the elevator revolution begins in 1854. In that year, in New York’s Bryant Park, the Exhibition of the Industry of All Nations—housed in a specially-constructed “Crystal Palace”–demonstrated the world’s cutting edge technology. One vendor present was Elisha Otis. He was showcasing his elevator prototype. In front of large crowds, he climbed onto the platform and hoisted it up a story or so. And then–dramatically–cut the rope holding it in place—producing terror that it would crash. And yet, it did not. The elevator hardly moved. His new safety break kicked in and rescued him from injury and obscurity. Since that dramatic display, the story goes, the elevator’s success shot upwards, now that fear of free-falling was gone. This story has been repeated ad infinitum as the pivotal moment for elevators and skyscrapers.

A Drawing of Elisha Otis Demonstrating his Safety Break to the Public in 1854. This drawing is widely circulated as “proof” that, until the public saw Otis’ safety break in action, they were afraid of elevators. However, according to author Andreas Bernard, this drawing was produced in 1978 in celebration of Otis Elevator Company’s 125th anniversary in 1978. It was an imagined recreation of past events and helped fuel the idea that Otis was the keystone in the elevator revolution. Image source: Wikipedia.

Myth Busting

Yet according to Andreas Bernard, author of the 2014 book, Lifted: A Cultural History of the Elevator, the story is not so simple. His search for contemporaneous reporting on this “viral” moment came up short. In fact, he finds, at the time, nary a mention in the press. He argues that for such a seemingly pivotal moment in history, hardly anyone seemed to care. He writes,

In the major American daily newspapers and magazines, the 1854 event showed up only in two marginal locations. In addition to the Scientific American article, a brief report appeared on May 30, 1854, in the New York Daily Tribune, which mentioned the daring of the inventor “who, as he rides up and down the platform occasionally cuts the rope by which it is supported.” No further contemporary traces can be found (just as there were no obituaries of Elisha Otis in 1861). Thus it is no exaggeration to say that the demonstration in the Crystal Palace, that “authentic great moment in architectural history,” went almost completely unnoticed by the public.

The story, evidently, is another case of history being written by the winner. Thanks to the diligence of Otis and his offspring, his company went onto to be one of the largest manufacturers of elevators in the world. In 1911, Elisha’s son Charles set out to “correct the record” about elevator history by writing his version of the events, and which minutely chronicled the display in the Crystal Palace. As Bernard writes,

The influence of … [Charles Otis’] text on the historiography of the elevator is obvious from the fact that after 1911, there was hardly a mention of the elevator’s origins that did not begin by repeating the story of the event in the Crystal Palace.

The First Skyscraper?

As a side note, this story has a familiar ring in regard to the world’s first skyscraper. The conventional wisdom is that it was the Home Insurance Building in 1885, designed by William Le Baron Jenney. But this notion seems to have been the product of Chicagoans winning the battle of historiography. The Home Insurance Building, while novel, could not, by today standards be fully described as a “skyscraper” in that it was not fully iron (or steel) skeletal structure.

At the time, many architects and engineers were developing technologies and methods in parallel. In the years after the first skyscrapers emerged in Chicago and New York, there was a battle within the community to claim the prize of “First Skyscraper.” Jenney argued it was his structure; while New York’s Bradford Lee Gilbert said his Tower Building (1889) was first. Others also offered proof they were the true innovators. In the end, through good marketing, Chicago remains the winner in our minds, but this claim highly debatable and far from conclusive.

The Birth of the Rent Premium

Once vertical transport revealed itself to be practical, however, another revolutionary moment was created. Likely, for the first time in human history, was an inversion in the economic and social value of higher floors. Before that, when climbing was the only way up, the top stories were naturally hard to get to. No one wants to climb more than a few floors; as a result, the highest floors were rented to those with the lowest ability to pay. Offices used them for storage or for their low-level clerks.

Rent Premium in 1900 versus 2019. Left: Rent ($ per room) for walk-up apartment buildings versus floor height in the Lower East Side of Manhattan in 1900. Right: Estimated sales price ($ square foot) versus floor height for luxury condos at 217 West 57th Street. The key takeaway: without elevators the higher floors were worth less to tenants because of the trouble of climbing stairs. Sources: Left: See *Building the Skyline*. Right: See Skynomics Blog post.

In a way, the elevator created treasure in the sky. Because vertical movement was fast and cheap, it generated a rent premium for the higher floors. That is say, the amount of rent paid, per square foot or meter, was higher as one rose up. Today, that premium in New York City is between 0.5 and 1% per floor. In other words, prices on 30^th floor of a skyscraper might rent for up to 20% more per square foot as compared to the same space on the 10^th floor. Developers realized if they could get their building occupants up there, they could reap more profits. And the race for height was on. This rent inversion was first noticed in New York City in 1870, when The Equitable Life Assurance Society built it’s 7-story headquarters near Wall Street, and which included two elevators.

The Value of a View?

How much of this premium is due to views, or increased social status, or more productive workers is still not fully understood; but what is clear is that people in big cities are willing to pay to be high in the sky. It’s also worth noting that this benefit also rests on our particular evolutionary history. Imagine that all humans had an innate fear of heights; that working in high-rise building automatically generated dread and anxiety? If so, the world would look radically different.

Elevator Dilemmas and their Remedies

The earliest elevators were driven by steam or hydraulics. And it was not until widespread use of electricity in the 1880s that efficient speeds were obtainable. Once this barrier was removed, however, a host of new problems arose. Faster speeds allow for taller buildings, which means more people, which generates more congestion and logistical problems in getting people to their final destinations. For example, there’s the problem of waiting times once you push the button in the lobby. Then there’s limits on how many people can fit in one cab. And when it is filled with passengers, it seems to stop on a million floors before you get to yours. Not to mention the fact it’s socially awkward to stand in a cramped box with 15 strangers.

The Pain Index

Keep in mind that, in theory, one can move people faster by creating more elevator shafts and this is certainly necessary for larger or taller buildings. But extra shafts are the bane of developers, since they eat up income-generating space. For the time being, we are going to hold the number of elevators constant and focus more on movement and speed. We will come back to the “shafts problem” in a future post.

The key challenge for efficient mobility is that of minimizing what has been referred to as the Pain Index—the total time to it takes from once you hit the button to when arrive at your final location. Evidently, however, it’s not clear what people hate more—waiting in the lobby for the elevator to arrive, stopping more inside the elevator, or getting into a crowded car.

Traffic Flow and Optimal Stopping

One of the key problems is that of peak usage times. For example, in offices at 8:30am, it seems every employee wants to get into the elevators at the same time. With the old-school call system, when multiple users push the call buttons at the same time, the elevators move to where they were called first. But when many buttons are pushed at the same time the system gets gummed up, increasing waiting time.

Computing technology and software programming has helped mitigate the problem of how to efficiently allocate car space during the day and based on different kinds of traffic patterns. Today, most modern elevator systems employ computer algorithms to minimize travel times, using what is called the Destination Dispatching System (DDS). In real-time, the system analyzes the input data–where the buttons where pushed–and makes a list of who to put in which cars and where the cars are to stop. If with conventional elevators waiting took over a minute, the DDS could reduce that time to half.

Elevator Waiting Times versus Traffic Intensity. The red line is waiting times for the traditional call-button method. The green line is the standard DDS system. The yellow line is a dispatch system created by KONE. Source: De Jong (2008).

Zoning and the Double Decker

For a given set of elevator shafts, the spaces can be used more rationally by the use of zoning and double decking. Zoning is the process of limiting specific elevators to operate only in predefined zones. One elevator can stop for local service, but another one say only goes from the lobby to the higher floors. Zones are normally kept to around 10-20 floors. This reduces the number of stops for the zoned cars and speeds up its return to the lobby. To allow for even higher heights, supertall buildings often have sky lobbies where an express elevator take you there and then you transfer to a separate elevator that operates only up high. For very tall buildings, another way to use the shaft space more efficiently is to have two elevators operate within the same shaft. One way to do this is to have one elevator car sit on top of another, creating the double decker. Odd-floor travelers enter the bottom car, while even-floor travelers enter the top car after walking up a ramp.

Cable Height

As buildings get taller, the amount of rope needed to connect the elevator car to the motor becomes longer and longer. This is a problem as conventional ropes, made of steel, can cease to be functional. In very tall buildings, nearly 70% of the elevator’s weight comes from the cable itself and when it gets too long it cannot support its own weight. Companies that manufacture elevator systems are thus in a race to develop new types of ropes that are both stronger and lighter. With conventional ropes the highest that one elevator car can travel is 500 meters (1640 feet; about 140 floors). After that, going taller requires transferring to a new elevator at a sky lobby. The Jeddah Tower is going to install KONE’s “UltraRope,” which has a carbon-fiber core, making it particular light and strong. With this rope, cars can now travel up to 1000 meters (3280 feet), and it pushes possible skyscraper heights upwards (is this the egg for first mile-high tower?).

Human Physiology

Then there’s the problem of the human body, with its delicate carbon-based controllers and pain receptors. To quote James Fortune, a partner at FS2 Consulting, which specializes in elevator designs for supertall towers, “The human body has various internal sensors that are sensitive to external motion forces, noise, and vibrations. These sensors provide constant feedback to the brain and are quite responsive to any “out of the ordinary” elevator vibrations or noises.”

In particular, humans are quite sensitive to the acceleration and deceleration rates, which can cause ear discomfort due to the rapid changes in air pressure. Fortune says that, “However, ear comfort and pressure changes do not usually affect healthy elevator riders unless the descent speeds exceed 10 meters per second (m/s) and vertical travel exceeds 500 meters. For this reason, virtually all the latest supertall high-speed lifts, with “up” travel speeds to 10 to 20.5 m/s, have a maximum “down” speed of 10 m/s. Some cutting edge elevators, such as those installed at One WTC add extra air pressure on the way up to help prevent the annoying ear-popping sensation.

A History of Speed

While it’s fun to focus on the history of speeds, the truth is that the fastest elevators in the world are mostly used for visiting decks and/or to give bragging rights to the developers and companies that install them. For most office buildings, the average maximum speed is about 21 feet per second (5.8 m/s). Nonetheless, as the technology for speed and comfort progresses, it is likely that their benefits will be more widespread. In 1913, the world’s tallest skyscraper, the Woolworth Building, had a maximum speed of 11.6 feet per second (3.6 m/s). In 1931 the Empire State Building, had a maximum speed of 20 feet per second (6.1 m/s). So in in some sense, the top elevator speeds for the typical building haven’t changed all that much. What has changed is that passengers can be much more rapidly moved based on logistical algorithms, zoning, and double deckering. The efficient allocation of occupants is really what allows for buildings to go taller and taller.

The Record Breakers

Be that as it may, the figure below demonstrates the history of maximum elevator speeds over the last century. The left figure shows the speeds (feet per second) for the world’s record-breaking skyscrapers. (Note the Shanghai Tower is also added to the graphs. It did not have record-breaking height but did have record-breaking elevator speed). This figure is clear: maximum elevator speeds have been rising over time. A back-of-the-envelope calculation shows that from the Singer (1908) to the Shanghai (2015), the maximum speed as increased at an average annual rate of 1.78% per year.

The right figure is speed versus the number of stories for the world’s record-breaking buildings. Again, we see a positive relationship. But, while the graph shows elevator speed versus height, we could be equally as justified in showing height versus speed, since we still can’t say which was the chicken and which the egg. All we can say is that the graph shows a strong correlation but says little about causality. Another thing, however, pops out in this graph: the world’s fastest elevators are not in the world’s current record-breaker.

The Burj Khalifa’s elevators can move at a speed of 33 feet per second (10 m/s) and the Jeddah Tower, under construction, is expected to be the same. These are much slower than the Taipei 101 and the Shanghai Tower. In other words, what these findings suggest, again, is that speed, in and of itself, is not paramount. Likely the cost of operating super fast elevators and need to maintain passenger comfort and efficiency of movement currently trump speed.

The Evolution of Maximum Elevators Speeds over the Past Century. Left: Maximum elevator speeds for the world’s tallest buildings versus year of completion. The graph shows that speeds have been steadily increasing since the early 1900s. Right: Elevator speed versus building heights. Notice the world’s fastest elevators are currently in the Shanghai Tower, not the Burj Khalifa. Source: The Skyscraper Center.

The Future of Vertical Transportation

What’s in store for the future? Certainly, we can say that the big five manufactures–Otis, KONE, Thyssenkrupp, Schindler, and Mitsubishi–will continue to invest in R&D to push the elevator envelope, thus encouraging developers to build taller. But what revolutionary technology comes next? Who knows? Likely futuristic buildings will have mag lev elevators with horizontal circulation. In 1957, Frank Lloyd Wright’s design for the one-mile high building called for nuclear powered elevators. But we’ll leave a discussion of these moon-shot technologies for the future, or rather, a future post.