Jean Nouvel’s Torre Agbar in Barcelona may be smaller than Foster and Partners’ Swiss Re, but it’s more vibrant, colourful – and basic. Martin Spring compares the two

Never mind the gherkin here’s the Geyser
Never mind the gherkin here’s the Geyser

If ever a building was set to beget a tribe of offspring around the world, it is that icon of a turn-of-the-century skyscraper – Foster and Partners’ sleek, curvaceous Swiss Re tower in the City of London. The first and most eagerly awaited daughter, the Torre Agbar in Barcelona, is due for completion in July.

In shape these are peas from the same pod – well, more like cucumbers from the same branch. Yet to label Torre Agbar as a Swiss Re clone is not just Anglocentric but downright misguided. The architect, you see, is royal gold medallist Jean Nouvel of Paris, who is of the same supermodern persuasion as Foster but gives his buildings a more ambivalent, surreal, teasing, even gutsy twist.

The idea that Torre Agbar should be a tower or a skyscraper in the American sense is far too staid and static for Nouvel. Instead his surging imagination has conceived it as the manifestation of the most basic, powerful elemental forces. As well as a giant phallus on a city scale, he has described his tower as “a fluid mass that bursts through the ground like a geyser under permanent, calculated pressure”.

Not just volcanic and sexual forces but air, fire and water are expressed in Nouvel’s building. Its precision-engineered geometry is counterpointed by splashes of colour that are vivid, irregular and cover the whole exterior. Further up the tower, swathes of blue and blotches of white encircle much of the tower, as if it had been absorbed into the Mediterranean sky. Lower down, the skin erupts in huge red flickers, as if reflecting the sunset, or even a city fire. Elsewhere, the colour subsides into watery ultramarine and misty green washes.

Shimmering skin

At the same time, this huge all-round mural of vivid colours is tantalisingly veiled behind a diaphanous outer skin of tiny scales, or louvres, of clear glass. “The surface of the building evokes water: smooth and continuous, shimmering and transparent,” Nouvel explains. “Its materials reveal themselves in nuanced shades of colour and light.”

Well might Nouvel comment: “The ambiguities of material and light make the Agbar tower resonate against Barcelona’s skyline day and night, like a distant mirage.” Yet behind this sophisticated interplay of clear transparent outer skin and colourful opaque inner skin stands a practical, low-energy and remarkably basic piece of construction.

This singular object will become the new symbol of barcelona the international city

Jean Nouvel

In practical terms, the outer skin functions as a weather screen that tempers the effects of sun, wind and rain. The inner skin, which is partially protected, is faced in a cladding material most commonly seen in out-of-town industrial buildings – profiled aluminium sheeting. The opaque skin is punched through in a seemingly random pattern by standard square or rectangular windows, many of them openable by hand.

Directly behind the profiled aluminium sheeting stands an even more low-tech material – in situ reinforced concrete. What’s more, the concrete is not deployed in a craftily assembled structural frame but in its most low-tech form, as a solid load-bearing wall up to 500 mm thick. As well as supporting the 35 storeys of office space, the massive concrete wall that encircles the building acts as a heat sink to reduce artificial heating and cooling.

Inside the tower, the offices will be arranged in elliptical open-plan floors, with a compact core for toilets, services and stairs offset from the centre. The six main lifts do not form part of this core but are banked directly behind it along the eastern perimeter of the tower.

When we get to the top eight floors that form the parabolic apex of the tower, the massive concrete walls are replaced by a glazed shell. As this shell is a non-load-bearing curtain wall, the office floors are set back from it and are supported on internal columns.

M Nouvel is not a man known for excessive modesty. And so it is with this building, of which he says: “This singular object will become the new symbol of Barcelona the international city.”

Being the city’s most prominent, as well as its most alluringly shaped, coloured and textured, landmark, he may well be right.

As for those building designers around the world who will never visit Barcelona, the tower presents an ingenious new model for low-energy, high-rise buildings. So, not a clone of Foster’s Swiss Re tower, more a rival.

Torre Agbar Barcelona

Architect Atelier Jean Nouvel
Location Edge of Barcelona’s city centre
Height 144 m, 35 storeys
Diameter 39.4 m (across longer axis)
Shape in outline Cucumber with straight sides and parabolic apex
Shape in plan Elliptical, with offset service core and six lifts along eastern side
Perimeter structure Solid insitu concrete shell up to 500 mm thick
External envelope Outer skin of fixed glass louvres and inner concrete shell clad in profiled aluminium sheeting separated by 800 mm air gap
Windows 4400 manually opening windows serving office space up to 26th floor
Apex construction Glazed curtain wall supported on orthogonal steel grid and enclosing but separate from top eight storeys
Environmental control system Low-energy combination of mechanical air-conditioning and natural ventilation
Gross floor area 30,000 m2 in tower
Construction cost £91m (total), £1920/m2
Completion July 2005

Swiss Re tower London

Architect Foster and Partners
Location Heart of City of London
Height 180 m, 41 storeys
Diameter 56.5 m (at widest bulge)
Shape in outline Seed pod with bulging sides and conical apex
Shape in plan Circular with circular central service core and offices separated by six triangular spiralling lightwellsPerimeter structure Diagonal steel grid
External envelope Glazed triple skin with ventilated cavity up to 1.5 m wide containing automatically controlled venetian blinds
Windows 792 electronically opening windows giving onto lightwells up to 32nd floor
Apex construction Glazed curtain wall supported on diagonal steel grid, enclosing but separated from two storeys including topmost domed hall
Environmental control system Low-energy combination of mechanical air-conditioning and natural ventilation
Gross floor area 61800 m2 in tower
Construction cost Undisclosed
Completion April 2004