THEME: Tall Buildings

Are Tall Buildings Sustainable?

BY Jane Wernick | November 2012

Earlier this year, Renzo Piano’s Shard was finally unveiled as the latest tall building to appear on London’s skyline. It has since attracted a mixed response; it’s certainly a striking statement, but one that towers alone, imposing itself upon one of London’s most historic boroughs. In this series of Think Pieces, we have asked a range of contributors to consider whether tall buildings are really the answer to our social, economic and environmental challenges of the future, in the context of continued population increase and global urbanisation.

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Is it time to give up the Tower Mentality in our Cities?

Historically tall buildings have been seen as a symbol of success and prosperity. However, we need to recognise that tall buildings do not increase the sustainability of our cities. We are learning to make buildings that consume less energy and have a lower carbon footprint, but we can use these techniques for all building heights. We should compare the best tall buildings with the best of the shorter.

San Giminiano – The towers represent wealth and success
Hans van der Boom©

It is often argued that there are benefits to a reasonably high density, where we can have easy access to everything we need. We increasingly appreciate the disadvantage of the lack of density around most cities in the U.S. where nearly everyone needs a car, but the benefits are not linear, and at densities above about 50 people per acre there are negative effects that become apparent.

Serge Salat – the founder of the Urban Morphology Lab in France – has done research that shows that, as well as density, the morphologies of the building stock (how our streets are laid out and the relative proportions of the buildings) must be considered in order to get a balanced view of energy and CO2. He studied housing in Paris and showed that the shape factor, which defines the amount of exposed building envelope per unit volume, and the amount of volume near the perimeter of the building that does not require artificial lighting, are the most significant parameters in determining the amount of energy required. A high shape factor means more energy is consumed. He showed the comparatively low rise areas of the traditional parts of Paris are more efficient than those with high rise developments. Other studies showed that 6 to 10 stories can achieve effective densities. The Indian architect, Charles Correia, has argued for many years in favour of low rise high-density developments in Mumbai for achieving the most humane and sustainable housing.

Density isn’t everything. A dense downtown business area, far away from a dense residential area can result in a higher carbon production as a result of the commuting between both sets of tall buildings. A less dense mix of the two, as in Paris where business and residential activities often occur side by side, can be more sustainable. Also, having tall buildings in the city for the wealthy, won’t necessarily increase the housing density, as many of those people have second or third homes, and their population count must be divided between their properties.

The best low carbon cities are not the most dense, but those which have a good distribution of amenities, are easy to walk around, and have good access to transport.

Density isn’t a valid excuse for tall buildings and this is important because there are many problems with this typology :

1. Taller buildings use more steel and concrete per square metre of occupiable floor space. A huge amount of energy needs to be saved in the running of the building if it is to match the efficiency of a lower one. It is less likely we can use timber the taller a building is. This is a shame as timber is a very low-carbon alternative structural material. The taller the building, the higher the embodied energy per usable square metre.

2. They need far more space for vertical circulation, which decreases the ratio of net to gross floor areas.

3. The additional lifts increase the energy required to run these buildings.

4. They are more exposed to wind and sun, leading to higher heat gains and losses for the same amount of insulation.

5. They cost more to build per square metre.

6. They cost more to maintain and repair per square metre.

7. They have an adverse effect on the mental health of those who live in them. This is particularly true in housing, especially for families with children. Crime and fear of crime is also greater in tall buildings.

8. As they get taller they also get wider, which makes the city less permeable at the street level.

The psychological issues are significant and important. Many high buildings have a sad history, with lack of maintenance, a propensity for crime, and isolation from the life and chances for social interaction at street level. Those that segregate residents by income tend to form vertical gated communities, bottling up key activities that might otherwise activate the public realm at ground level. The fact that the running and maintenance costs are higher is particularly problematic for those on lower incomes. In this age of cuts it really can’t make sense to saddle cash-strapped councils and the less well-off with buildings that are going to deteriorate if they are not maintained.

Tall buildings have a bad effect on their neighbours:

1. The ground level wind effects get worse as they get taller, and can’t be totally reduced by canopies.

2. They cast large shadows, which take away sunlight and pleasure, and block access to solar power. We should introduce Solar Rights legislation.

3. They produce ‘Canyon Effects’ whereby pollutants from motor vehicles are trapped and concentrated at street level, reducing air quality. The population’s exposure to traffic pollutants in New York’s urban street canyons can be up to 1000 times higher than exposure to a similar quantity of emissions in other urban settings.

Tall Building Shadows from the Burj Khalifa, Dubai
Yron Yang©

Security remains an issue. Post 9/11 some corporations may not want to be near target buildings, and might just favour Paris’s medium development. Tall buildings tend to have more ducts for services. As well as being a potential breeding ground for mould, particularly in hotter climates, they are also vulnerable to biological terrorist attack.

We will probably continue to build a few tall buildings, but we should concentrate on creating urban and cultural frameworks that allow us to have good personal interactions, provide places for chance encounters, acknowledge and respect our ageing population, and most importantly allow us to experience frequent contact with nature. In any wealthy society, what a rich family with children aspires to is a detached house with a garden. They might want a high-rise flat as well, but we need to focus more on the needs of the majority.

We need to balance the needs of the planet, the environment and people. We need to achieve maximum efficiency with minimal resources, and at the same time achieve social harmony. We need to concentrate on designing our built environment so that it provides opportunities for happiness. I don’t see any evidence that tall buildings give us the best chance of achieving this.

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Jane Wernick FREng Hon FRIBA FRSA CEng FIStructE FICE is a structural engineer who has specialised in the design of structures which play a large role in the total architecture of the building. She worked for Ove Arup and Partners from 1976-1979, and from 1982-1988. She worked for Birdair Structures Inc. from 1980-1981. She was Principal in Charge of Ove Arup & Partners’ Los Angeles office from 1986-88 and was an Associate Director of Ove Arup & Partners from 1989. In 1998 she founded Jane Wernick Associates Ltd.

Jane is a member of numerous panels such as Design Council Cabe, the EDGE and the Building Futures steering group, where she edited the \’Building Happiness – Architecture to make you smile\’ publication; a series of essays discussing contemporary ideas and debates around the nature of the built environment.