The lightwells in 30 St. Mary Axe read as dark, spiraling stripes from the exterior (top). The atrium spaces they create aid communication between floors (middle) and bring daylight deep into workspaces (bottom).
Foster’s “Towering Innuendo” is a Big, Eco-Friendly Hit.
Architectural Record, June 2004
Londoners were once skeptical of 30 St. Mary Axe, the tapered bullet that has clambered into the skyline over the last two years. It’s usually called the Gherkin, a title standing in for a variety of unprintable descriptions, or the Towering Innuendo. But as its sleek, now-complete form bobs and weaves into view around the city, locals have reportedly developed a fondness for the first tall building to be erected in the City of London (its financial district) in 25 years.
At 40 stories, it would not be regarded a large tower in most of America’s downtowns, but in the lowrise, finely grained cityscape of London, its 500,000 square feet look gargantuan. How could a tower so unconventional in nearly every respect look like a big friendly alien rather than a menacing intruder?
It’s no airplane-napkin sketch fast-tracked into reality. On the site was the Baltic Exchange, a lowrise pile that was severely damaged in 1992 by a bomb planted by the Irish Republican Army. A debate about whether the building could be saved consumed a few years. Foster & partners, with its client, Swiss Re, recognized that a replacement could be proposed only if it was clearly superior. Extensive local consultation led to an approval process that nevertheless consumed two years.
The curving profiles that have become a distinctive signature of the firm’s work in recent years respond to local environmental conditions and the ability of the architect and its consultants to deploy sophisticated computerized modeling and analytical tools. In this case, the Foster team, including Ken Shuttleworth, who recently left the firm, came to the circular plan and tapering section because it lets wind slip by, according to Rob Harrison, an associate partner, which reduces lateral loads on the structure. More important, the shape minimizes the tendency of tall buildings to focus gale-force winds on unwitting pedestrians at street level. While the form puts the largest floors above the prevailing 10-story-high norm, where views open across the city in all directions, Foster slimmed the tower on the lower floors as well, which opened the dim, narrow, surrounding streets to daylight. The trim ground floor left space to carve out a handsomely proportioned plaza, offering a shortcut through the City’s twisting blocks for cell-phone wielding dealmakers headed to the Tube. Such sensitivity to the public realm helped the building survive the tough planning review.
The diagonally gridded exterior binds the building form visually (imagine the bulging-gut look it would have with vertical mullions). It actually emerged as Foster and his team worked out the most remarkable feature of the building, the six-level lightwells, six per floor, which spiral continuously upward. Reconciling the five-degree rotation in the lightwells generated the diagonal grid of the structure and the cladding, according to John Brazier, the project director at Arup, the structural engineer.
Foster has long designed to acheive a more humanely social work environment. In the Commerzbank tower (Frankfurt, Germany) he pioneered the use of skygardens, restful oases - for informal meetings, for sipping a coffee, or just thinking - hovering high above the city. While conventional real-estate wisdom might deem the light wells a frill, they are integral, in Foster’s hands, to a strategy that addresses the chief criticisms of tall buildings as work environments: that the big pancakes of space neither offer the amenities highly valued staff want nor encourage collaborative work.
For Swiss Re, Foster offset each level of the light wells to offer terrace overlooks. The advantage is simple if a bit abstract: If you see people on other floors of a tall building, you are much more likely to feel they are part of your group - that you are in this business endeavor together. You’ll feel invited to move from floor to floor rather than remaining psychologically sealed in your own.
On this much tighter site, the social spaces are narrower, more intimate than at Commerzbank. “Everyone’s conscious that the balcony edges are the best spaces in the building, with great views up and down the light wells,” said Sara Fox, who has directed the building project for four years after working to build the firm’s innovative American branch in Katonah, N. Y. These areas are reserved for coffee bars, copy centers, and other informal-gathering functions, rather than devoted to departments. “We spent a lot of time with staff talking about the interconnectivity this makes possible,” she said. As people move into the building, she adds, “they come up to me and say, ‘Oh, now I get it.’ ”
Workplace quality and energy conservation are inextricably woven together in the building. “We wanted an environmentally responsible building,” explained Fox. “We didn’t have a checklist; we asked Foster to explore what was possible.” The commitment was meaningful for the company well beyond corporate altruism. “We are in the reinsurance business,” Fox explained. “For us, sustainability makes excellent business sense because we pay out claims on behalf of clients for floods, heat waves, droughts. To the extent that these claims are related to global climate warming, it is only prudent of us to contribute as little to it as possible.”
The lightwells bring daylight deep into the space, even to those positioned closest to the core. (“That’s a lifestyle issue - quality of workplace for staff,” explained Fox.) The quality of daylight from the floor-to-ceiling exterior windows is also high, because heat gain from the sun is trapped in the space between the external curtainwall and a second glass wall placed just inboard of the external column diagrid. The insulating layer not only saves energy, it permitted the use of clear glass, protected by blinds in the thermal layer. By contrast, the glass in the light wells needed to be deeply tinted (visible on the exterior as dark, spiraling stripes).The triangular light wells divide the floors into six 2,500 square foot (on average) rectangular wedges, offering an efficient shape for laying out offices or open-plan workstations.
With automatically opening windows, the light wells conduct fresh air. The interior glass wall is left out at the balconies, so that, fresh air penetrates the entire floor (one much deeper than the naturally ventilated norm) without mechanical assistance. Air warmed by occupants and equipment rises up the chimneylike light wells, drawing in outside air. The round floor plate aids airflow by molding a distinct zone of negative air pressure on the leeward side, which draws in more windward-side air. Although the building is mechanically heated and cooled, the natural-ventilation scheme should leave the systems idle much of the time, accounting (with the daylighting) for much of the building’s reduced dependence on climate-altering fossil-fuel combustion. (Local air-handling units allow mixed-mode use by zone and by floor, as well.) According to Brazier, current local guidelines for low-energy offices targets electricity use of 175 kilowatt hours per square meter. He expects Swiss Re’s new building to knock up to 25 kwh off that.
Swiss Re occupies about half the building; the remainder has yet to be tenanted in a moribund real-estate market. Nevertheless, the completion of 30 St. Mary Axe - and its acceptance - portends a deluge of new office buildings, according to pundits. As they vie for height, the towers announced to date compete on the basis of amenity, energy responsibility, and aesthetics (the designers’ names are all household ones: Piano, Grimshaw, Kohn Pederson Fox, Rogers, Wilkinson).
None of the long-announced towers has yet begun construction. Fox echoes their developers in claiming that more towers will get built. “London is really the financial center of Europe. Most firms, particularly in financial services, want to be at the heart.”
London and New York, both seeking dominance of global finance, now offer a study in contrasts. “Location is so much more important in the UK than in New York,” explained Fox, noting that a consensus has developed that London’s City must grow to remain vital.
New York, which perfected the skyscraper downtown, has ceded tall-building innovation to Europe and Asia. It is far less sure that the proximity enabled by tall buildings still pays off. Will tenants balk at innovations that raise rents? Is a horizontal, dispersed business model more prudent in a world wracked by terrorism?
The next few years will tell which model comes out on top. The stakes are certainly high. If a great number of American financial figures start taking meals in Swiss Re’s “nosecone” restaurant (it’s private; sorry), where breathtaking city panaoramas open through the spidery fretwork of the building’s diagrid crown, you can be sure London’s (and Foster’s) lessons won’t be lost.