It was thought to be blasphemous to build higher than the a church spire.

The stories of the old testament warned against reaching too close to the heavens.

The builders of the tower of Babel declared: “Come, let us build us a city and a tower

with its top in the heavens.

And let us make a name for ourselves, lest we be scattered upon the face of the whole

earth” But god punished them for building a monument

to humanity and not to God by confusing their language so they could no longer work together.

This story is used as the source of our world's languages for the religious and some still

use it as an argument against our modern world, but it has interesting undertones for the

development of our cities.

For centuries the church spire remained as the focal point of most western cities.

The Trinity Church was the largest building in New York until 1890 when the New York World

Building was completed.

This marked an end to the Cathedral dominated skylines of many cities across the world.

Those church spires served as a symbol of piety, but The New York World Building's

height allowed Joseph Pulitzer to expand his growing business without having to find a

large swath of land on the outskirts of the city.

Growing taller served a practical purpose and it still does in many cases.

It's that demand for space that truly drives up the average height of buildings in cities.

Cities like Hong Kong do not have any supertall buildings, but the average height of buildings

in Hong Kong is among the highest in the world and that is largely driven by the lack of

space available.

Hong Kong is confined by the sea on one side and the Chinese border on the other while

having a very mountainous landscape.

There isn't a huge amount of land to build on.

This forced buildings to grow taller to accommodate the city's population.

.

When Hong Kong needed to expand their International Airport there was little space available.

Instead they decided to level two islands outside the city to create a new artificial

Island, where the new airport is now located.

This project added 1% to the total surface area of Hong Kong.

When space is limited humans are forced to get inventive to cope, but in many cities

across the world space is not an issue and these cities usually decide to expand outwards.

This is called urban sprawl and it's been a topic of debate lately, with calls to stop

this decentralisation of cities.

Urban sprawl requires little micro-management of resources, you simply continue to expand

current utilities and roads and approve buildings on cheaper undeveloped land.

It's an easy solution to a growing population, but it creates many problems of it's own

and is completely unsustainable as populations grow.

You cannot simply keep expanding the city and allowing those problems to escalate.

It has huge environmental and social impacts.

One of the most obvious, which my friend Wendover Productions spoke about in his last video,

was an increasing commute time.

With an increasing city diameter the distances we have to cover to reach the city centre

increases and it is incredibly difficult to serve all of these far flung suburban neighbourhoods

with adequate public transport.

This results in a city dependant on the car, our least efficient form of transport.

This not only has a social impact, as long commute times are one of highest and most

controllable factors that affect our happiness, but The average American spends 17,600 minutes

behind the wheel a year, much of that is spent in gridlock traffic, that's equivalent to

spending almost an extra 37 days at your traditional 8 hour 9 to 5 job, but it also has a direct

impact on pollution and air quality in the city too.

That's 17,600 minutes of a car polluting the environment.

Reducing a city's dependence on cars reduces our carbon footprint on this world.

Urban sprawl affects our environment in other ways too.

Spreading our cities creates water distribution problems.

Here in Ireland it is thought that up to 50% of the treated water is lost through pipe

leakage and that problem is not unique to Ireland.

In 2010 it was reported that 3.3 billion litres of water was being wasted in the England and

Wales through pipe leakage.

Reducing the sprawl reduces the length of pipes needed and thus reduces the chances

of leakages and the problem can be attenuated further by creating buildings with self sustaining

water supplies.

This is becoming a growing trend and consideration among engineers.

LEED or Leadership in Energy and Environmental Design is one of the most popular green building

certifications used world wide.

It rates how resource efficient buildings are in their construction, energy use and

water use.

The Taipei 101 was awarded LEED's highest certification with a platinum certificate.

It achieved this with it's own dedicated water management systems and low-flow water

fixtures.

This design ideology helped the Taipei 101 to decrease it's potable water consumption

by at least 30% compared to the average building consumption, saving about 28 million liters

of potable water annually.

When you also consider that in America landscape irrigation is estimated to account for nearly

one third of all residential water use, totaling nearly 9 billion gallons of water per day.

It would be vastly more sustainable for a world where water is in ever increasing demand

to create cities where we have a larger percentage of LEED certified high rise residential buildings.

This goes beyond just environmental impacts, there are a number of socio-economic motivations

to creating more high rise buildings too.

I pointed out that the urban sprawl results in longer commutes and the roads and public

transportation needed to facilitate those commutes are not free.

They need to be maintained and built with your tax money and while building up is more

costly, that cost and risk is usually incurred on private contractors and the costs of building

up starts to decline once you reach a certain height.

To build a skyscraper there are a number fixed costs, but many of these costs do not increase

with the height of the building.

Fixed costs like the cost of land, legal fees and design costs can be offset by building

higher.

If the building is built on a 100 square metre plot of land and the building has 40 stories,

each floor only takes up 2.5 square metres of land.

That has obvious economic advantages, especially when you consider design and material costs

only start to go up when you reach around the 40th floor and that critical height is

likely to go up as technology improves.

Buildings like the Burj Khalifa may be just exuberant displays of wealth, but they do

serve as technology demonstrators.

For 25 years the tallest building in the world was the Sears Tower, now known as the Willis

Tower.

It uses a bundled tube structure, which maximises the amount floor space, but if we scale this

building to the size of the Burj Khalifa.

It's floor space would be dominated by structural elements and the interior would have no natural

light.

As mentioned in my last video, the buttressed core of the Burj Khalifa provides the structural

integrity needed to reach these heights, while maximizing both the window access and usable

space.

This is vital knowledge and experience to have to allow building heights to keep growing

while keeping costs down.

So you may be thinking why aren't there more high rises buildings.

If there are all these benefits there must be reasons that we aren't building more

of them.

We will learn why after this quick side note

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So they primary reason we aren't building higher is because of city planning and regulatory

problems.

Take New York's growth in the early 20th century as an example, building heights were

growing and many were unhappy with it.

At the time 5th Avenue was filled with stately mansions, homes to the wealthy families of

New York like the Carnegies and Rockefellers.

They worried that unless building heights were restricted, 5th avenue would turn into

a dark cannon, overshadowed by these towering behemoths.

These worries led to 1916 zoning resolution which allowed buildings to grow in height,

but restricted their width as they grew.

This is one of the primary reasons so many buildings in New York built during that era

taper towards their top.

It was a measure to prevent buildings from blocking the sunlight below, but the regulation

had loop holes and architects quickly exploited them.

Between 1916 and 1960 the city's zoning code was amended 2500 times.

The 1961 Zoning Resolution brought in strict rules and introduced a new floor to area ratio

rule that restricted buildings heights according to the district they were.

The floor to area ratio set how much floor space could be built on a plot of land.

A floor to area ratio of 2 means you can build a 2 story building on your full plot or a

4 story building on half your plot.

R1, R2 and R3 districts are low density zones like Staten Island and the Jamaica Estates

in Queens and they have a floor to area ratio of 0.5.

Where as major thoroughfares in Manhattan are R9 and R10 districts which have floor

to area ratios of 7.5 and 10 respectively.

This floor to area ratio rule put pressure on designers to allocate more space to open

plazas or other public spaces around the building to faciltate a taller tower, whereas the 1916

zoning laws resulted in tiered buildings that started right on the sidewalk.

The 1961 zoning code encouraged privately owned public space to ease the density and

claustrophobia of a high rise city and I think we can all agree that is a move in the right

direction.

Zoning regulations like this are important to prevent brainless growth that destroy a

city's character, but sometimes they are overzealous and prevent modernisation altogether.

Take Washington DCs zoning code that has been in place for over 100 years with little change.

The Height of Buildings act of 1910 prevents any building beyond 40 metres in height.

That is incredibly restrictive and it has resulted in a city where the tallest structure

is a giant stone obelisk and this thing.

Even with a relatively small population, Washington has some of the worst traffic in the US.

A study released this year by INRIX found that the people of Washington waste an average

of 75 hours per year in traffic.

That means their journeys take 75 hours more than if there was no congestion.

They were second only to Los Angeles, who waste an average of 81 hours a year in traffic.

LA is often singled out as the key example of this problem of unchecked outward growth.

It was a key theme in the movie “Her”, where the car dominated urban sprawl of the

present is juxtaposed with a vision of a glossy, clean, high rise future for LA.

The main character Theodore lives in a highly developed downtown LA.

He lives in a high rise building and works in a high rise building.

He's able to walk between them and cars seem to have ceased to exist,he instead uses

the extensive metro system to get around.

The movie even designed a futuristic subway map of LA.

To create this vision of the future, the producers digitally enhanced the cities existing skyline.

While also mixing in shots from present day LA with numerous shots from Shanghai's Pudong

district, like this pedestrian sky bridge which allowed Spike Jonze to film Theodore

wandering through the urban jungle without having the cars at street level interfering

with the illusion of a city that has transcended the need for personal transport.

That transformative change seems implausible and not likely in the near future, but cities

can undergo metamorphosis when money and regulations are not an issue.

Take the mid-19th century renovation of Paris as an example.

Paris was once described by one of it's residents as “an immense workshop of putrefaction,

where misery, pestilence and sickness work in concert, where sunlight and air rarely

penetrate.

A terrible place where plants shrivel and perish, and where, of seven small infants,

four die during the course of the year.”

This is an incredibly stark description of Paris, when present day Paris is often fawned

over for it's wide boulevards, amazing architecture and extensive public transport system.

Paris of old was plagued with problems caused by the outdated planning of it's medieval

past.

Paris was in need of renovation and Napolean III made it possible by giving the money and

power needed to Baron Haussmann.

He transformed these narrow streets and old dilapidated buildings into spacious boulevards.

(Rue de Rivoli)

He revamped all of these streets in red and created two new parks for the cities residents.Napolean

III and Haussmann helped transform Paris into the charming city of light that 16 million

tourists now visit every year.