The computer-generated image above shows how the Swiss Re building, with its eye-catching spirals (top), will alter London's skyline. Credit: SWISS RE

London's gherkin

The architect Norman Foster has taken 'green' building to new heights.

The latest addition to London's skyline is distinctive for more than aesthetic reasons. The 40-storey, 180-metre-high cigar-shaped office building has also been hailed as a milestone in ecologically friendly architecture. Designed by Norman Foster for the reinsurance firm Swiss Re, the tower has now reached its full height and is due to be completed later this year.

The building is arranged in a series of spirals, each twisting five degrees per storey as they snake upwards. The curved atria or 'lightwells' thus created allow air to circulate throughout the structure — the building's smoothly curving glass skin features opening windows — and the oxygenating indoor gardens that punctuate these atria also prevent the atmosphere from becoming stale. The design cuts air-conditioning costs to a fraction of those in conventional skyscrapers. The lightwells also allow maximum penetration of natural light, reducing the need for electric lighting.

The design is socially friendly to those working in and around the building. Although its shape might seem gratuitous — it has been variously dubbed the 'Erotic Gherkin' and the 'Towering Innuendo' — the aim is to reduce the structure's physical impact on its surroundings. The building's curves will reduce reflected light and prevent winds from being deflected to ground level, as it is by rectangular buildings. And the tower's tapered form allows for more public open space at ground level.

The design has its origins in Foster's collaboration in the early 1970s with Richard Buckminster Fuller, the architect and humanist who lent his name to the football-shaped carbon molecules whose structure resembles his famed domes.

In 1971 the pair came up with a theoretical concept called the 'Climatroffice', to feature storey-spanning spaces containing indoor gardens for the circulation and oxygenation of air. Traditional walls and roof are replaced with a 'curvilinear' glass covering, to minimize building materials. Both of these features are faithfully brought to fruition in the Swiss Re building, which is effectively a high-rise incarnation of the Climatroffice.

The idea of glass-skinned buildings was not new even in the 1970s — in 1960 Fuller built a 21-metre-high geodesic dome known as the 'Climatron' to provide hot and humid conditions for the Missouri Botanical Garden's collection of tropical plants.

Although the Swiss Re tower's environmental credentials are unmatched in London, it is not Foster's first 'green' skyscraper. Europe's tallest building, the 259-metre Commerzbank tower in Frankfurt, which was completed in 1997, also borrows from the Climatroffice concept by incorporating a series of nine indoor 'sky gardens'. The gardens — four-storey open spaces — surround a central atrium that pierces the building's entire height. This huge column allows air to circulate throughout the building, providing natural ventilation in place of air conditioning.

Other British architects are also keen to see their country mirror the devotion to ecological considerations shown by continental Europe. David Marks and Julia Barfield, the architects responsible for the London Eye observation wheel — another of the less conventional shapes on London's skyline — recently unveiled their Skyhouse design as a response to urban planners' demands for affordable housing solutions. The proposed 40-storey towers, which would be composed of petal-shaped wings to make maximum use of natural light, could pair high-density housing with economical energy costs. The contemporary design could also go some way towards subverting the traditional British notion that high-rise living is undesirable.

Ironically, it seems that the world's most skyscraping nation, the United States, is lagging behind in the endeavour to build greener towers. Of the final two proposals competing for New York's Ground Zero site, neither has an ecological focus. Instead, the Lower Manhattan Development Corporation seems determined to make the simple, symbolic statement of erecting the tallest tower in the world. But committing to an environmentally progressive building is a noble response to a terrorist attack — as those in London's financial district are well aware, the Swiss Re building stands on a site whose previous incumbent, the Baltic Exchange, was destroyed by an IRA bomb in 1992.