Introduction

The most quoted definition of Sustainable comes from the Brundtland Commission report created in 1987:

'Development which meets the needs of the present generation without compromising the ability of future generations to meet their own needs’. The definition of a tower or skyscraper, which is a large-scale intensive building type, generally regarded as being over 10 storeys and which can be of commercial, residential, hotel or mixed use. However the authors Jacobs & Manzi and Dunleavy use a definition of high-rise as “flats and maisonettes in blocks of six or more storeys.[1] The Council on Tall Buildings and Urban Habitat defines a tower as a building in which all the systems are distinct due to its height. The Sustainable Tower is therefore a combination of these definitions and a practical solution to the environmental, social and economic problems that are now confronting our cities. 

The need for sustainable development has been argued over for many years and most governments are recognising this need after global initiatives such as the Rio Summit and the Kyoto and Montreal Protocols. As the human population increases, we consume more resources and cause more destruction. This is no longer a theory but a fact that governments and business are waking up to.  

Throughout the 20^th century, the urban population has grown from 15% to 50% of the global total and this number is expected to increase to perhaps 70% over the next hundred years[2]. The author and lecturer, Herbert Girardet has calculated that cities built on 2% of the earth’s surface, use up 75% of the planet’s resources whilst release just as much waste.2 Urban Developers, Municipal Governments and Building Designers have a responsibility to provide a viable solution that will address these issues of density, space and sustainability.  

Corbusier argued that skyscrapers have a relatively small area footprint and can therefore provide more open space than low-rise development. More people can be housed vertically in a smaller space than horizontally in the same space. The United Nations claims that skyscrapers can lower transportation costs, which will result in less energy consumption. There is a general recognition that the tower has the potential to provide the necessary solution to many urban problems but how can a tower be sustainable? 

Many building designers are rising to this challenge and some have made it the focus of their professional pursuits. Students and research organisations are dedicating their studies to the problem. As a result of current environmental and economic problems, the language of sustainability has become unavoidable for architects, building engineers, governments and developers.   

This state of the art report shows that tower designs are aiming for sustainability but no one has yet to design the ultimate sustainable tower that satisfies all environmental, social and economic ideals. However, it is certain that if the dreams and plans for future designs and developments of tall buildings integrate the processes and technologies currently being developed to deal with high-density urban living and environmental problems, then the result will be socially, economically and environmentally sound communities.

Brief History of the tower

The Rise of the Tower 

The desire to reach for the sky through architecture has existed since antiquity when our ancestors built the Tower of Babel, the Colossus of Rhodes, the pyramids of Egypt and Central America and ancient temples of the East. Until recently, the tower was used to make a statement of power by the existing establishment, from towers of gothic cathedrals to the Eiffel tower to the Empire State Building.  

It was the mass urbanisation of the late 19^th century that caused a global increase in tower building and the development of technologies that form the basis of today’s architecture. One of the earliest tall buildings in Europe, at 49 meters was a residential building in London called the Queen Anne Mansions, which was built in 1884. One of the tallest office buildings was called 'Het Witte Huis', which was completed in Rotterdam in 1898.  

The major force for constructing tall buildings came out of the new metropolises of in America, where the building of skyscrapers became the most convenient way to create a large amount of property out of a moderately small area of land. They were “a machine that makes land pay” as defined by the designer of the Woolworth Building, Cass Gilbert in 1900.[1] 

In the late 1800s social and economic circumstances helped to propel the growth of skyscrapers in major American centres, mainly Chicago and New York. All businesses wanted offices near the city centre of town, but there wasn't enough space so architects began to design vertical spaces rather than horizontal. The drive was mainly economic as expressed by a leading property authority in the Architectural Record in 1893, “An office building’s prime and only object is to earn the greatest possible return for its owners, which means that it must present the maximum of rentable space possible on the lot, with every portion of it fully lit”.3  

This early economic drive and existing technological limitations meant that early towers had shallow depths with large windows for natural daylighting and windows that could open for natural ventilation3. These were early practices that are now being revived for maximising energy efficiency.

Most early towers at the end of the 19^th century were constructed out of bricks but this meant that many buildings could not be higher than 10 storeys as the load bearings made the lower walls too thick and impractical. The development of mass iron and steel production helped to advance the development of the skyscraper. Architects could now work with narrow and lightweight metal beams that saved space and could support more weight than the brick. When mass steel production became more feasible buildings became taller as it is a lighter and stronger material than iron. 

As buildings became taller the necessity for vertical transportation became apparent. This technology emerged during the industrial revolution and made the growth of skyscrapers possible. The first lift was installed in New York's Haughwout Department Store in 1857 and since that time the technology has been a major component of skyscraper design.  

The lift structure proved to be a challenging aspect of tower design. As floors are added to a building, the building's occupancy potential increases which will mean more lifts. But valuable floor space is lost for every elevator you add due to the amount of space that lift shafts take up. The correct ratio of floor numbers to lift numbers became an important factor in designing a tower.  

Building safety was also a major issue in the design of skyscraper and the advent of new fire-resistant building materials in the 1800s also assisted the growth of towers. The development of the modern skyscrapers included the installation of sprinkler equipment, which is now commonplace.

Building regulations or lack of regulations combined with economic drivers to advance the rise of the tower in the two leading metropolises of New York and Chicago. In New York where there were no height restrictions at the turn of the last century, the tower was tall and slim with a floor plan arranged around a compact core of circulation and services.3 Whereas in Chicago, heights were limited and the building type was rectangular with a large light court in the centre or at the back.3

In the late 1800s social and economic circumstances helped to propel the growth of skyscrapers in major American centres, mainly Chicago and New York. All businesses wanted offices near the city centre of town, but there wasn't enough space so architects began to design vertical spaces rather than horizontal. The drive was mainly economic as expressed by a leading property authority in the Architectural Record in 1893, “An office building’s prime and only object is to earn the greatest possible return for its owners, which means that it must present the maximum of rentable space possible on the lot, with every portion of it fully lit”.3  

This early economic drive and existing technological limitations meant that early towers had shallow depths with large windows for natural daylighting and windows that could open for natural ventilation3. These were early practices that are now being revived for maximising energy efficiency.

Most early towers at the end of the 19^th century were constructed out of bricks but this meant that many buildings could not be higher than 10 storeys as the load bearings made the lower walls too thick and impractical. The development of mass iron and steel production helped to advance the development of the skyscraper. Architects could now work with narrow and lightweight metal beams that saved space and could support more weight than the brick. When mass steel production became more feasible buildings became taller as it is a lighter and stronger material than iron. 

As buildings became taller the necessity for vertical transportation became apparent. This technology emerged during the industrial revolution and made the growth of skyscrapers possible. The first lift was installed in New York's Haughwout Department Store in 1857 and since that time the technology has been a major component of skyscraper design.  

The lift structure proved to be a challenging aspect of tower design. As floors are added to a building, the building's occupancy potential increases which will mean more lifts. But valuable floor space is lost for every elevator you add due to the amount of space that lift shafts take up. The correct ratio of floor numbers to lift numbers became an important factor in designing a tower.  

Building safety was also a major issue in the design of skyscraper and the advent of new fire-resistant building materials in the 1800s also assisted the growth of towers. The development of the modern skyscrapers included the installation of sprinkler equipment, which is now commonplace.  

Building regulations or lack of regulations combined with economic drivers to advance the rise of the tower in the two leading metropolises of New York and Chicago. In New York where there were no height restrictions at the turn of the last century, the tower was tall and slim with a floor plan arranged around a compact core of circulation and services.3 Whereas in Chicago, heights were limited and the building type was rectangular with a large light court in the centre or at the back.3

Regulations influenced the shape of the skyline in these two cities once again in the 1920s. The laws that gave rise to the twin spires of the Chrysler and Empire State Buildings were meant to protect light and air accessibility and taller buildings had to be stepped back as they rose in height, causing a wedding cake effect.3 Situation in cities such as Tokyo, Hong Kong, Shanghai and Kuala Lumpur at the end of the 20^th century and beginning of the 21^st The 20’s boom in skyscraper growth ended between 1931 and 1934. Over 26 million square feet of office space was completed in Manhattan but much was left unoccupied as the Depression set in. Buildings built during this era did not fare well, such as the Empire State Building, which did not turn a profit until 19503. By the 30’s skyscrapers had been built all over the world including Toronto, Vancouver and Montreal as well as Sao Paulo, Rio and Buenos Aires, Melbourne and Brisbane. Skyscrapers were being built in Hong Kong and in Shanghai the P&T Group alone built 5 towers. In Madrid the National Telephone Building was erected and eight other European cities had separate or twin towers that ranged from 14 to 28 storeys.[1]  

It wasn’t until after the Depression, World War Two and the Post War recovery period that the rise in towers began again during the 1950s and '60s. Technological advances during this era culminated in massive projects like the Sears Tower and the World Trade Centre. Glazing advances in 1950s and '60s, provided curtain walls that were made almost entirely of glass and this started the familiar looking towers of glass with spectacular views that defined the metropolises of post-war America. During this recovery period in the UK, the tower was viewed as an economical solution to the problems of social housing.   

Further technological advances took place in construction during the latter half of the 20^th century. This included improvements in steel structure, high performance concrete, high-speed lifts, artificial climatisation and other factors[2]. During this time Europe began to catch up with tower building in cities such as Frankfurt, London, Paris, Rotterdam, Warsaw and Moscow. 

The tower has remained a solution to intensive urban development and land limitations as a result of population growth and market expansion. This became apparent when the eastern economies began to grow during the 80’s and 90’s5. Recently, nine skyscrapers have been built in China, and three in the United Arab Emirates and three in Malaysia where the tallest building now exists. There are many others in the works. We have therefore seen a that is not unlike Chicago and New York at the turn of the last century.

Decline of the tower

The last tower boom in the US was created during the Reagan years in the US, which created new urban monoliths from Atlanta to Los Angeles. But of the 20 American high-rises that reach 900 feet or more, none have been built in the 90’s. This may be due to the fact that many of the greatest sources of wealth are no longer steel magnates or shipping barons who want to show their power in the towers they erect, but rather high-tech companies based in the Silicon Valley. The high-tech corporate architecture reflects a decentralised and non-hierarchical culture that is horizontally spread out and landscaped 

In the UK the decline of the tower began years ago when it became apparent that the many tower blocks built in the 50’s and 60’s for social housing were of low quality. The image of the tower is blighted by such social prejudice so that when someone in the UK says they live in a tower block they are almost pitied. Alternatively, if you lived in a tower in American you would be envied. In some cities in the Far East the tower has also become identified as a symbol of mass low quality housing. 

These image problems only add to a growing list of argument against the tower that are causing the decline of the design of tall buildings: 

• The skyscraper represents globalisation and decreases the capability for regional and cultural identity through architecture
• It is perceived as being in opposition to the intimacy and cosiness of the suburban experience
• Low-rise living is considered to promote better community interaction
• Skyscrapers are considered risky or too expensive in certain regions due to local climatic and environmental conditions such as areas that are susceptible to earthquake or high storm forces
• There will always be transportation and energy issues, as skyscrapers will always depend on rural areas to provide raw materials and agricultural produce
• The status symbol of high-rise living is causing the mass migration to the cities in the first place
• The skyscraper is a highly capital and energy intensive built form, which causes a negative environmental impact due to the high infrastructure costs, amount of materials required, construction costs, operational and maintenance needs
• The construction, ownership and maintenance are usually private and centralised, which can deny a necessary sense of connection and community

Post September 11^th 

The most influential event to cause a decline in the interest of towers was the terrorist attacks on the World Trade Centre on September 11^th, 2001. This has caused a re-evaluation of the value of towers around the world but mainly in the US where attitudes are already changing regarding the building form. The result has already impacted the following aspects of the construction and operation of skyscrapers. 

Security 

Architects, engineers and property managers have been developing a wide variety of measures to protect the inhabitants of office buildings from terrorist attacks as a result of the events of Sept. 11. Some of these measures are already in effect, while others are still in the planning stages. For example, building designers are taking measures as simple as locating air intakes near the top of structures, to deter attempts to introduce poisonous gas or biological agents. Other measures include making buildings more bomb-blast resistant through materials and building techniques. This may involve taking such steps as encasing steel columns close to the ground in concrete, to make them more resistant to blast and fire, and designing in diagonal beams amid the vertical and horizontal structure to transfer loads if part of a building is damaged. Some other anti-bomb-blast tactics include adding extra steel reinforcing bars to concrete surfaces vulnerable to attack, so that even if the concrete is shattered by a blast, the broken chunks are held in place and do not fall downward causing additional damage. The new attention to avoiding potential disasters may also involve redesigning the basic shapes of buildings to protect the vital core of the structure, which contains the elevators, stairwells and utility lines. Future designs may also provide multiple routes for electrical power, telecommunications and other utilities, so that damage to one part of it does not cut off these services to the entire structure. [1] 

Current operators of existing properties are increasing security measures and making sure they are as visible as possible. A building with barriers and noticeable access control is not as likely to be attacked than one with a lenient program. Security advisers are requesting for better control of building access through identification of tenants and visitors and control of the parts of a building to which people have access. The lobbies of office buildings need security desks and barriers to prevent people from getting into the building without being cleared. Turnstiles in lobbies are becoming more common in tall buildings and there are now turnstiles at 4 Times Square and the Reuters building.6 

All building issues are now a concern for security. For example central air-conditioning plants are difficult to purge after a fire or other occurrence contaminates the air in a building. Project managers are recommending that buildings be designed with separate air-conditioning units for each floor.6 

Insurance 

Owners of skyscrapers have recently had difficulties renewing their insurance policies after the September 11^th disasters. Some companies that have been or want to be insured against terrorist acts say such coverage is drying up, and if it is available, the premiums have gotten sky-high. Many bank loans and expansion projects have been cancelled or are no longer fully insured. The biggest impact may be on tenants of the buildings as they face rent increases.[2]  

Energy 

In a roundtable discussion documented in an issue of The New York Times Magazine, a group of building and planning experts considered what could be built on the site of the World Trade Centre. The Architect William Pedersen of KPF Architects, made the following statement about a building based on new forms of energy. “I’m interested in the concept of buildings that can generate power from natural, renewable sources,” he said. “This is the sort of thing that should have happened regardless of the attack, but this gives a reason to start taking it seriously. If there’s one thing we’ve learned from this, it’s that we don’t want to depend on these volatile, far-off places for energy....” 

The Architect continued by saying that each face of an energy-efficient building should be utilized differently to harvest sun and wind energy. “The tall building is a perfect structure to deal with wind turbines and wind generation. Photovoltaic cells are ideally situated on tall buildings because they have a tremendous amount of surface area.” [3] 

Height 

The Construction Institute of the American Society of Civil Engineers recently completed a report called ‘Rebuilding the World Trade Centre.’ The report suggests that whatever is rebuilt on the World Trade Centre site must be secure against much more sophisticated bioterrorism attacks and, because of both safety and economics, should be no more than 50 or 60 stories tall.[4]

Vertical Transportation  

In the business world very tall skyscrapers have lost some of their appeal, simply because they don't make good economic sense. In high-rises of more than 70 stories, the number of elevators needed to ferry thousands of people huge distances uses up available floor space and this creates an equation of diminishing returns as the building climbs higher.9

The UK Tower Block 

Between the end of the war and the beginning of the 1990s 6,544 multi-storey blocks were built in the United Kingdom. These provided just over 400,000 high-rise homes for up to 800,000 people. The real boom years for tower block building were from about 1953 to 1972.[11] However, a widespread social stigma developed towards UK tower blocks shortly after these boom years, when the nation realised the extent of the low the quality of these constructions.  

This stigma could have originated from a British class and welfare system that has always attempted to compartmentalise the poor which has only succeeded in creating an institutionalised poverty. It may have began with the clearance procedures of Disraeli’s Public health Act in 1875.[12] 

After World War II, government policies were introduced to house the poor and the Conservatives tended to favour multi-level housing of flats

. In 1956 the new Conservative government policy restricted urban councils from using suburban and rural sites for re-housing so vertical urban density was the only solution. Economic factors lead to the common solution of providing high-rise blocks that economised on quality.12  

As the chart shows below, it actually cost more to build high and therefore Architects were under pressure to cut the costs of building flats even though there was a subsidy encouraging their increased height12  

Comparative costs of low-rise and high-rise flats: 

Source: From figures give to MoHLG (1958)12

The major cost-cutting opportunity was in the quality and number of access routes and arrangements12.
 

The National Sustainable Tower Blocks Initiative has noted that throughout the UK, the tower block has a very negative image and is one of the least desirable forms of housing. In 1992 The National Tower Block Network documented the following problems related to tower blocks after almost 10 years of working with tower block communities[13]: 

·         Inadequate heating systems

·         Lack of safety for children

·         Tenant isolation / depression

·         Inadequate play facilities

·         Asbestos

·         Lack of community facilities

·         Poor fire safety

·         Racism / racial harassment

·         Inadequate or unreliable lifts

·         Dampness / condensation

·         Building defects

·         Lack of security

·         Poor layout / environment of estates

·         Cockroaches

·         Other vermin

The first seminar of the National Sustainable Tower Block Initiative in 2000 resulted in the addition of the following problems to the list1: 

• Noise, litter, and refuse – problems resulting from a ‘clash of lifestyles’
• The fear of crime as well as crime itself
• Poor reputation and stigma
• The range of different conflicting interests involved – the tenants, the landlord, funding organisations and contractors all have a stake of some sort
• Allocations policies – the tenants’ priority is suitable neighbours, but for financial reasons the landlord may want to let to whomever
• Enforcing obligations and responsibilities of contractors
• Timescales for the provision of services

Further general problems involving social exclusion include1: 

• Poor health
• High unemployment
• Poor services (including shopping facilities and transport links in and out of the estate)

Local authorities own most of the tower blocks in the UK. Recent stock transfer agreements mean that a number are now owned or managed by housing associations, and this is likely to increase in the next few years. Many high-rise residents pay rent to their local authority or housing association. The majority of tower blocks in the UK cater for social housing need and this creates the social stigma that they are not appropriate for the upwardly mobility that our culture promotes.

Densification in Hong Kong 

One of the densest human populations on earth exists in Hong Kong. Everyone lives in concrete towers and the average density is 280,350 people per square mile.[14]  

A population boom happened during the 70’s and 80’s and despite a continuous development in high-rises, life was difficult. In Kowloon ‘Walled City’, a family of four would live and work in one room and children had to play on the roof or the alley. Natural light was difficult to obtain and often people needed to share public washrooms.[15] 

The construction of the Kowloon Walled City was contracted by the landlords and was very haphazard without any control or the submission of drawings to the local authority’s building department. In an area of 2.6ha, 300 buildings with 10 to 14 storeys were built. The structure had different levels and the upper floors were connected so one didn’t even have to use the street to get from one building to the next.15  

There was some public supply of water but most people dug wells and pumped water to the upper floors. There was no organised drainage and so ditches were used. Most of the buildings had electricity from the public electricity company as most of the units relied on artificial lighting and air-conditioning. The roof became the only place for exercise, relaxation and fresh air.15 

The benefit of this densification became the community bonding, as many of the residents of Kowloon Walled City came from the same part of China and therefore shared a common background. This link, combined with the close living quarters established a good sense of community. An anti-crime watch system was also set in place so the area had a low crime rate. 15 

To those who are not use to it, the sight of these towers conjures up images of a dystopian future of overpopulation and poverty. The towers here are not the symbol of luxury they are in the US. They are often worse than the decaying tower blocks of the UK. The reality of these buildings has contributed to the negative image of the tower but has not noticeably hindered the perception of high-rise living as much as the tower block in the UK or the experiences of September 11th.