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  • This episode of Real Engineering is brought to you by Brilliant,

  • a problem-solving website that teaches you to think like an engineer.

  • We've been hearing about it for years.

  • The 21st century is the era of urbanization.

  • In almost every country around the world,

  • people are packing their bags, and moving into cities at record rates.

  • This is a global phenomenon,

  • across the spectrum of developed and developing economies.

  • Approximately 54% of people worldwide

  • now live in cities,

  • 30% more than in 1950.

  • And projections show that urbanization,

  • combined with the overall growth of the worlds population,

  • could add another 2.5 billion people to urban populations by 2050.

  • In many countries, the largest cities are growing faster than their smaller counterparts.

  • Rural cities, towns and villages are being cannabalized

  • to facilitate the demand for jobs in these urban centres.

  • For better or worse,

  • we are increasingly becoming an urban world.

  • Thus, it's no surprise that the demand for city housing is skyrocketing.

  • Prices to rent or to buy are reaching, for many,

  • unobtainable heights.

  • Savos, a global property firm,

  • published its list of cities with the highest cost of accomodation around the world,

  • with the usual suspects ranking high.

  • New York, Hong Kong, London, Tokyo, and Paris

  • all consistently in the top 5.

  • But even smaller cities, like Dublin, are experiencing serious housing crisis,

  • with many people unable to afford to live

  • near their places of work.

  • With jobs flooding back into Dublin after years of recession

  • there is an incredibly high demand on urban housing.

  • In Ireland capital, housing prices has risen

  • by average of almost 50% in 5 years

  • and the number of listings are at a record low.

  • Some attribute Dublin housing price increases to a lack of housing supply

  • due to investors hoarding property,

  • and increased AirBnb, or vacant land not being developed.

  • while these are all definately factors

  • even if they were resolved, Dublin would still be falling short

  • of the 25,000 new units needed every year to meet

  • the current demand.

  • In recent years, construction in the city has increased significantly

  • but the return of cranes to the skyline, but many are

  • commercial units and apartment buildings are simply not being built

  • fast enough, and in enough numbers to make a dent in the demand,

  • causing rent prices to rise to the point that many

  • young Irish are once again having to consider

  • whether Ireland is a place they can build a future.

  • Continuing the ritual brain drain of

  • our country's youth to not so green pastures.

  • The government has responded to this problem unsuccessfully,

  • with ridiculous attempts to ban rents from rising,

  • a solution akin to banning a sick patient's temperature from rising.

  • The only cure for this fever

  • will be to increase the supply of housing,

  • that is, increase the supply of housing while minimizing cost.

  • Let's first focus on optimum height.

  • While some are calling for high rise buildings to Dublin

  • with the idea that it while increase density and greater supply,

  • buildings that are too tall don't translate into

  • affordability as they cost too much to build.

  • In theory, taller buildings reduce square meter costs of floor space

  • the higher you build, and increase the overall

  • returnable revenue from a single plot of land.

  • However, the cost increases as you build higher and higher.

  • Lift systems, fire prevention measures, water supplies

  • and pressurization and heating and cooling systems

  • all add to the cost of high rises.

  • Costs like these lead to a U-curve in regards to the cost per square meter

  • and height, where the cost per square meter initially decreases

  • with an increase in height, and then starts to increase

  • after the height reaches a certain point

  • due to the increased engineering demands.

  • Every curve therefore has a bottom-out point.

  • This bottom-out point is different in every city

  • and varies widely even within the city. But on

  • average the lowest cost per square meter in Shanghai

  • and in the Netherlands for example, is around 8 stories.

  • In Hong Kong, thanks to the limited land area increasing

  • land costs, it's around 12 stories.

  • The additional cost of engineering can be marginalized

  • by high costs of land, making in worth while to build higher.

  • Take the extreme example of 432 Park Avenue,

  • the tallest residential building in the world.

  • Built on the site, the historic Drake Hotel once occupied,

  • centrally located with Central Park views, the site became one

  • of the most valuable plots of land in the world at

  • $520 million. Now it goes without saying

  • this building was not constructed for the average man.

  • It has over 85 floors with 38,000 square meters of usable floor space,

  • but only 104 units

  • for people to live in, each costing millions of dollars each.

  • But the point stands

  • where there is exceptionally high demand, you can build higher.

  • The cost of land in Dublin doesn't come close to those of Manhattan

  • or Hong Kong though. So in most cases,

  • the bottom of our U-curve, ie. the cost effective height to build to,

  • will be between 6 and 8 stories.

  • With a recent Irish government report even suggesting

  • as high as 12 stories in some areas.

  • Let's next focus on minimizing the building costs

  • of these buildings. One of the primary causes of

  • increase costs with increased construction height

  • is the necessity of using floor space

  • for the structurally integral building core, which keeps the building

  • standing and houses elevators and other services.

  • While there are many ways to design the shape of the building,

  • certain floor plate designs end up being more desirable

  • than others to maximize usable space. Say that the

  • net area of the floor plate of this building is 1400 square meters

  • The core of the building of this shape

  • and size would need to be around 335 square meters

  • This gives a gross area of usable area

  • of 1,065 square meters

  • and thus a net to gross ratio of 1.31.

  • So a design like this is stylish, but when you analyze the

  • space efficiency, it's not great for maximizing floor space

  • A building like this

  • seems like it might have a bit more usable space

  • but the building core is still taking quite a bit of space

  • compared to the livable floor area. This design's

  • net to gross ratio is around 1.26.

  • And a building with this shape may not be as exciting,

  • but it's core area is minimized compared to the usable space.

  • Its net to gross ratio is only 1.14.

  • Which is about as good as it gets and is exactly

  • the floor plan of 432 Park Avenue.

  • While variety and expression of building design are important,

  • these elements invariably add costs and require

  • careful design consideration.

  • When affordability is an issue, simpler designs are better.

  • Wall to floor ratio is also a critical

  • measure of cost efficiency. It expresses the perimeter length

  • of the wall that has to be constructed for every unit of floor area.

  • So from a cost perspective,

  • the lower the ratio, the better.

  • Using simple geometry, we can see that a 3x3 square

  • has a total perimeter of 12 meters.

  • This would have a wall to floor ratio of 0.33.

  • A cross shape with the same area of 9 square meters,

  • has a perimeter of 20 meters. This would have a wall to

  • floor ratio of 0.45.

  • When constructing buildings, this simple principal is the same.

  • The more perimeter wall needed per floor area,

  • the more expensive things get.

  • A comparison of Asian and London towers provides an interesting

  • contrast in approaches wall to floor ratios.

  • Tall Asian buildings score between 0.30 and 0.35,

  • while London buildings score between

  • 0.35 and 0.60

  • with the majority above 0.45.

  • This is because the Asian buildings have larger, more regular floor plates

  • with centrally located cores. So the design

  • of our tower has huge effects on our cost

  • but so does construction techniques.

  • Traditionally, towers are built using repeating floor design

  • with molds called formwork, being used

  • to cast the concrete structure. Despite this

  • essentially being an automated assembly line,

  • it can still be labor intensive and slow,

  • and is exposed to variabilities of site and weather conditions.

  • Prefabrication and offsite construction is

  • increasingly becoming an appealing option, but this can offer

  • high precision solutions created in factory conditions

  • and often reduce on site delays and help progress construction

  • even in a market with a skills shortage

  • On some construction projects in Dublin, already

  • concrete products and timber frames are being fabricated offsite

  • and assembled onsite. An extreme example of

  • this idea of prefabrication is being used in China

  • where a company called Broad Sustainable Building

  • built a 30 story building in 15 days

  • for a cost of $1000 per square meter.

  • and later built another 57 story building

  • in 19 days.

  • The building pieces are fabricated

  • in sections at two factories in Hunan.

  • From there, the modules complete with pre-installed

  • ducts and plumbing for electricity,

  • water, and other infrastructure are shipped to the site

  • and assembled like Legos, or flat-pack IKEA furniture

  • The company is in the process of franchising this technology

  • to partners in India, Brazil, and Russia.

  • What it's selling is the world's first standardized skyscraper.

  • One of the primary cost drivers for skyscraper

  • are the labor costs for specialized workers.

  • By outsourcing much of the construction work to

  • safer, controllable environments like this, we can reduce

  • the costs. In a country like Ireland, where many of its skilled construction workers

  • were forced to immigrate to Australia, New Zealand, and Canada

  • during the economic crisis, many of which have not come home.

  • This may well be a solution that can help with construction.

  • Regardless of building techniques,

  • policies need to change in cities like Dublin to facilitate

  • quicker cost effective builds. While not being completely blind

  • to future implications of relaxing regulations.

  • Currently, 1 car parking space per unit is required

  • for every apartment. In a city center location,

  • where we would hope to move toward public transport solutions,

  • this is a completely unreasonable regulation to have in place.

  • Especially when you consider the impact of costs

  • it has, with some reports estimating that this adds

  • 30,000 euro per car parking spot to any building.

  • With our city populations growing more rapidly every year,

  • we cannot hold onto past ideals. While the optimum

  • height for minimizing the cost of apartments

  • may be 6 to 8 stories, we've discussed the benefits of building higher

  • beyond just the minimization of cost and how other

  • cities have transformed themselves in a past video.

  • Building higher facilitates cost effective public transport,

  • reduced commute times, and creates a more livable city.

  • We simply cannot continue allowing urban sprawl

  • to be our solution. It is an unsustainable

  • solution to a problem growing faster than we can keep up.

  • We simply need to look at the ever growing

  • rate of homelessness in cities like Dublin for proof of this problem

  • In a city that lost hosting for the largest

  • tech conference in the world, due to a severe lack

  • of infrastructure, the Dublin city council deemed it

  • sensible to refuse planning permission

  • to this 22 story hotel

  • on Tara Street, on the grounds that it would have a

  • "significant and detrimental visual impact on the city skyline"

  • A skyline dominated by two industrial chimney stacks

  • while functional, modern building that are

  • desperately needed in the city, are continually blocked.

  • This isn't a problem exclusive to Dublin.

  • San Francisco. A city

  • notorious for skyrocketing costs of accommodation has

  • an average building height of just 3 stories.

  • Mostly due to similar restrictions in building heights.

  • Washington D.C. has some of the worst traffic in the U.S.

  • and it has height restrictions blocking anything taller than its national monuments.

  • In larger cities with restrictive height regulations,

  • you can almost be garunteed

  • socioeconomic problems will follow.

  • In all reality, this problem has so many fascets beyond

  • just engineering challenges.

  • This is a problem that primarily effects young people,

  • and those who already own their home, have little

  • interest in devaluing it, by allowing high rise developments near their home

  • and thus increasing supply.

  • There are political motivations and many more factors that change

  • why and how bubbles like this occur in different cities,

  • but if we are going to build a sustainable future, we're

  • going to have to rethink how we build and plan our cities.

  • Perhaps we can start using machine learning algorithms

  • to analyze and suggest changes to optimize our cities.

  • Machine learning is a fantastic tool for when humans

  • fall short of a complicated challenge, and you could learn