New design techniques turn landmark London tower ‘green’ 

Copyright: David Lawson– Property Week Sept 1999

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There is something very British about reactions to  plans for landmark  buildings in the UK. In any other country, spectacular proposals for London's bomb-blasted Baltic Exchange site would raise a buzz of excitement. We invent a ludicrous nickname -  'the erotic gherkin' - and assume  it is an egotistical fantasy.

   But the Swiss Re HQ - still widely known as the Millennium Tower after previous plans for the site - encapsulates a remarkable number  of ideas for solving problems which affect most office buildings. And  perhaps most important for the property industry, it follows rigorous investment criteria. This building will be both green and mean.

   'There were a lot of eurekas when doing the designs,' says Robin Pennington of  architect Foster & Partners. 'Every time we came up with one idea we found it opened more possibilities.'

 The distinctive ovoid profile, for instance, is not the expression of some designer's artistic pretensions but based on hard commercial logic. The narrow base opens up space for public use, the wider middle creates larger floorplates and the tapered peak softens the skyline profile.

 An aerodynamic shape also creates  pressure differentials which help move  air up the 590ft building. The diagonal facade is not just decoration. Each of the 40 floors is rotated a few degrees from the one below, leaving spaces at the edge which act as a  spiral stack.  Slots  in the external glass tap external pressure differences to help drive air upwards. The stack  ventilation means that for most of the year the air conditioning can be switched off.

 That means it will be much cheaper to run, says Pennington. Details have not yet been finalised but energy consumption could be around 140 KWh/sq metre/year - around a third less than a conventional office building.

  The circular profile is another commercial decision. It offers the big, open floors demanded in the City,  averaging 1,400 sq metres (15,000 sq ft). Normally, that would cut off large areas from  daylight, so each floor has a cog-like form, with six fingers radiating from the core.

 Gardens fill the spaces, offset by the spiral to benefit multiple floors rather than as deep, individual atriums. This creates different climatic conditions in each one. They are cut off every six floors to control air movement and fire risks in a similar fashion to the way the firm built the Commerzbank HQ in Frankfurt.

 Sir Norman Foster says it is 'unlike any office building so far conceived'. That may be  an overstatement considering the number of unrealised dreams scattered around drawing boards but it is  certainly a pioneer among commercial buildings. Architectural ingenuity has replaced high-tech mechanics.

  One nagging doubt could be  that boundaries are being pushed forward by a highly motivated owner-occupier rather than conventional developer. Swiss Re is committed to environmentally friendly buildings and Fosters admit it has learned a lot from the financial groups other offices.

  But Pennington insists that no-one has been allowed to stray into green fantasies. 'This is part of Swiss Re's investment portfolio. At every stage we  have had to demonstrate that it meets standard investment criteria,' he says.

  On the one hand, that means a low running cost and high-quality working environment to attract staff and enhance productivity. But it also shows in conventional planning grids used within the revolutionary shape, such as the 16.5-metre window-window depth.

  Does that mean it could be repeated by speculative developers? 'I don't see why not,' says Pennington. 'Green buildings should attract premium rents because they are cheaper to run and offer better staff conditions. Remember that attracting quality staff is the reason why occupiers choose city centres and they make up a much higher proportion of overall costs than buildings.'

 Another landmark building by Foster on the other side of the Thames has raised similar howls about artistic fantasy upstaging economic facts. The circular Greater London Assembly building seems to step completely outside commercial criteria, but again the shape derives from hard logic.

  Once the decision was made to use extensive amounts of glass to symbolise the transparency of a democratic body at work, it made sense to employ variations on a sphere, which has 25% less surface area to build up solar gain than a conventional cube.

  The building leans back to the south, with stepped floor plates to give natural shading. Other areas will be protected by some kind of binds. Not all light is bad, of course. Photovoltaic panels will collect some energy to power pumps which draw water from bore holes to cool the building.

  Heat from computers, lights and people will be collected in the core and recycled out wherever it is required at the periphery. Overall energy consumption will be a quarter of a typical high-specification office building and there will be no boilers nor chillers.