Tall Structures with High Aims
Text: Jakob Schoof
The future of building lies in the vertical direction – at least that's what a look at the constantly growing metropolises of the world suggests. A symposium concerned with greater sustainability of high-rise buildings took place at the University of Stuttgart.
"Tall Buildings for a Sustainable Future" (TBSF 2012)" was a home match for the initiator of the symposium held in Stuttgart, Werner Sobek, in terms of content as well as location. Sobek has concerned himself with the question of how to make tall buildings more sustainable for years in his work as a structural engineer and façade designer, as a university lecturer and book author.
The organisers of the Institute for Lightweight Structures and Conceptual Design (ILEK) headed by Sobek, managed to gather some very prominent figures in the Swabian capital for the occasion. These included Christoph Ingenhoven and Helmut Jahn – probably the most eminent German (or of German descent) high-rise building architects. Other distinguished speakers from industry were Wong Mun Summ from WOHA in Singapore, Jack Carter from Renzo Piano, as well as Peter Oborn, deputy chairman of the major British firm Aedas. Representatives of the German higher education and research landscape included Manfred Hegger, Alexander Rudolphi, Klaus Sedlbauer and Werner Sobek himself.
What makes a tall building sustainable?
The core question of the symposium was how tall buildings can be designed more sustainably. Most of the speakers agreed that there is no all-inclusive answer to the question whether tall buildings can or cannot be sustainable per se. A look at the growth of many metropolitan areas in the world clearly indicates that there isn’t any way around the construction of tall buildings in many places in the future.
Yet tall buildings function differently to most other building types. They are basically small cities under a common roof (or rather: behind a common façade), which need to be planned as such. The sustainability issue not only includes aspects like energy consumption for heating, cooling and lighting, but also things like mobility planning and green spaces, social structures within the building, grey energy and so forth.
In addition, economical and design aspects need to be taken into account. Christoph Ingenhoven reported on major discussions that he had to engage in with the investor of his "Uptown Munich" project (which accommodates the head office of the mobile phone service provider O2) in order to obtain permission to round the corners of a tower. The design change meant a loss of three square metres of floor space per storey and corner – how could Ingenhoven justify this, so the investor. Questions that reduce a design-related decision to a mere figure.
Potentials for financial savings however often lie in less obvious areas. Such as through a simplified planning process using BIM (Building Information Management), a point put forward by Siegfried Wernik from Léon Wohlhage Wernik based in Berlin and chairman of the buildingSMART association. The idea behind BIM: a three-dimensional model of a building is created in a computer at the beginning of the planning process, which is then successively linked with all the information about components, their quantities, properties and prices. If all the designers involved in the project work on the same model, hundreds of interfaces and thousands of euros in building costs can be saved. Although BIM is not exactly predestined for large-scale projects, it is still at an early stage of development in many respects. An example related by Wernik which illustrates this is that ecological balance data still cannot be included in BIM systems satisfactorily until today.
Energy consumption is of course also an area with a lot of potential for saving. Examples include LED lighting, or – not insubstantial for tall buildings – the elevators. With around-the-clock operation and illumination, these have quietly turned into veritable energy hogs over the years. A remedy is promised by new equipment presented by Thomas Lipphardt from Kone: much like in a hybrid car, the propulsive energy is returned to the system during the braking process, and much like in a modern computer, there is a deep sleep mode instead of energy-intensive standby operation.
Another saving strategy involves the replacement of building materials through intelligent design. The environment ultimately also profits from this: the more energy efficient the operation of buildings, the greater the relative importance of the grey energy in the construction of the building. Most of this is in the shell of the building – mainly in the materials concrete and steel. For example in "The Shard", London's recently completed and currently tallest skyscraper designed by Renzo Piano, structural engineers were able to reduce the thickness of the foundation plate from four to three metres. The associated saving in CO2 emissions corresponds to the annual emissions attributable to over 100 British households.
All the same? About the design diversity of tall buildings.
A truism voiced by critics of globalisation and big cities is that the metropolises in the world have become more and more alike. Tall buildings are specifically identified as the driving force behind this conformity. That this does not have to be the case was demonstrated at the symposium by project examples from Europe, Australia, South America and Asia, that could not be any more different.
Wong Mun Summ presented the (mainly residential) high-rise buildings in Singapore, Bangkok and other tropical major cities in Asia, designed by his office WOHA. These are characterised by lush façade greening, intelligent strategies for air infiltration and ventilation, as well as a socially compatible design in the form of "streets in the sky". The office has also taken part in competitions in Germany and adapted its strategy to the local conditions: WOHA suggested a façade greening system based on hop plants for a residential construction near Henninger Tower in Frankfurt. The jury did not however appreciate this reference to the company that originally built the tower and which is also responsible for its name – Henninger Brewery – enough to select WOHA's design.
In contrast to Singapore, Australia suffers from a shortage of water. The City of Sydney therefore seeks to save about one quarter of its water demand through more efficient sanitary facilities by 2015; a further 12% cut is planned through multiple use of water. Christoph Ingenhoven's “1 Bligh” office tower is a progressive example of how this aim can be achieved. The building has its own small sewage treatment plant that not only treats grey water from the building itself, but also waste water from the municipal canalisation, making it usable for cooling the building.
A further feature of this Ingenhoven design is the double skin façade, which is already established in Germany. It was a novelty for Australian high-rise construction on this scale however and allows a movable solar protection system to be used in the space between the façades. The system protects tenants from the north sun when it is high in the sky, while still permitting a clear outside view during 90% of office hours. This is a further reason for Ingenhoven to continue to use fully glazed façades for tall office buildings – after all the view is part of the incentive for tenants to pay premium prices. The fact that some people design tall buildings with perforated façades is incomprehensible to the architect from Duesseldorf.
The people living in "Torre David" in the Venezuelan capital Caracas have a completely different set of problems. The 45-storey office building, which last made the news as winner of the Golden Lion at the Architecture Biennale in Venice, has an eventful history behind it and possibly a promising future ahead. Planned in the early 90s, the investor died just before completion of the building, and the subsequent economic crisis in the country sealed the fate of the unfinished project. Years of vacancy followed, until a community of homeless locals occupied the tower and quickly transformed it into a kind of vertical favela. Parts of the glass façade were dismounted and sold; the remaining holes were closed single-handedly using cheaper materials. In the meantime, a well-functioning micro-cosmos has been created inside the building – with own shops and hairdressers, improvised sports halls and fitness studios and a lively social network based on neighbourhood help and bartering.
To ensure a secure future for Torre David, the Venezuelan Alfred Brillembourg and the Austrian Hubert Klumpner, who are both directors of Urban Think-Tank as well as university lecturers at ETH Zurich, developed a low-tech efficiency-boosting concept for the tower. Their ETH colleagues Arno Schlueter and Jimeno Fonseca contributed an energy concept based on façade-integrated micro wind energy systems, a new water supply system and an unpowered elevator system – operating solely with the counterweight of the people using it. It's hard to say who deserves more admiration: the self-help energy of the inhabitants or the effort by the architects to further optimise an actually working system.
The most recent example in the range of projects presented at TBSF 2012 was the Shard by Renzo Piano, which is now London's tallest building. After a preparation, planning and construction period of almost 14 years, the structure is now complete. The official opening was held on 5 July 2012 and the roof platform will be opened to public in February 2013.
Right at the top: London's highest viewing platform. The crystalline structure is made up of 72 floors, including offices, restaurants, a hotel and a significant proportion of apartments. The uppermost tip of glass is not accessible to the public. It was originally supposed to accommodate a gigantic recooling system, which however became superfluous because of the availability of increasingly efficient cooling aggregates on the market.
The Shard was optimised ecologically in many different places: the support structure is for instance composed of a sequence of concrete – steel – concrete – steel from the bottom to the top, because this was found to be the most efficient solution in terms of material use. As far as placement of the elevators in the core of the building was concerned, the architects and engineers fought for every square centimetre of space, which was in turn reflected by material savings in the core walls. The CO2 emission associated with cement production was reduced by addition of slag sand.
The mobility energy that this building saves is in another league: a total of 48 parking spaces are allocated for the 8,000 residents and employees; to make up for this meagre number, London Bridge Train Station and the eponymous bus station are situated right next door (and were also newly constructed in the course of the project). The social benefit of the project should not be ignored according to project manager Jack Carter at Renzo Piano Building Workshop: the taxes and charges that the investor had to pay Southwark, the London borough in which the tower is located, added up to over 100 British pounds per person living in the borough. Money which is now available for schools and social housing, for example.
The ILEK announced that the symposium series is to be continued in the future. Whether the topic will again be about tall buildings is not yet known. In its present form, the symposium is a source of inspiration and an opportunity for exchange for all established and prospective designers of tall buildings. The idea of combining fundamental knowledge with examples of built projects from all over the world could however be reassessed: some presentations at TBSF2012 were simply too basic for a reasonably experienced audience to learn something new from.
A missing aspect that should perhaps be focused more on in future is what can be learnt from the success or failure of previous tall building designs. Since building monitoring is absolutely imperative for any sustainability certificate, it would be appropriate for energy designers, auditors and sociologists to report on findings derived from monitorings, user satisfaction surveys and analyses of socio-spatial impacts of tall buildings.