When your mission is saving Planet Earth you can’t waste time on understatement. Thus the new £15m education centre at the Eden Project is, according to Tim Smit, the creator of the environmental showcase, “the finest modern building in the world”.
On a dank winter morning, approaching the Eden site, in a former china clay pit in Cornwall, it’s hard to get quite so carried away. With its patinated copper roof and timber structure, the new addition, dubbed The Core, sits a little awkwardly alongside Eden’s bulbous glass and steel “biomes”.
But it’s when you get inside that the building comes alive. More than just an assembly of classrooms and exhibition spaces, The Core has been designed to express much of what Eden is all about.
Its most conspicuous feature is a soaring timber frame, built from 400m3 of red spruce glulam and doing what few structures have done: swinging upwards and sideways in two planes to create an arching double spiral that drops to ground level, supporting the roof and enfolding the whole space.
There are 21 weight-bearing beams curving in one direction, 34 in another, from a central ‘trunk’. The sweeping geometry was based on the mathematical Fibonacci sequence, in which each number is the sum of the preceding two (1, 2, 3, 5, 8, 13 etc). It’s a growth pattern found in many natural forms and the basis for the ‘golden section’ used by artists as the basis of composition. It just looks ‘natural’ and, according to Eden general manager George Elworthy, that’s one reason why visitors are so struck by it. “Most say the building has an extraordinary feel. You can’t quite describe it; it just makes you feel good.”
The Core, which opened last autumn, took two years to complete. Construction was overseen by joint venture contractors Alfred McAlpine and Sir Robert McAlpine, with the original Dome architects Nicholas Grimshaw & Partners, and engineers SKM Anthony Hunt and Buro Happold playing key roles.
But the in-house project team was typically Eden, blending creative, scientific and practical skills. It included director of learning Dr Jo Readman (a botanist) and Elworthy (a former hotelier), working alongside Peter Randall-Page (a sculptor). “We wanted to involve artists with the architects and craftsmen to see what would result,” said Elworthy, adding that Randall-Page’s carving of a giant ‘seed pod’ from a 160-tonne lump of Cornish granite will eventually be the centrepiece.
Readman wanted a space that worked for the public and schoolchildren but would also “redefine education” by telling part of the “sustainability” story through its construction. On top of this, said Elworthy: “Everything that we build has to look world class and iconic.”
The preliminary designs, he admits, did not set the world á Ü alight. It was only after Readman spent a day with the architects, talking through the processes of plant growth, that the spiral pattern emerged. “The original idea was for the building to comprise two opposing Fibonacci spirals,” said SKM Anthony Hunt senior engineer Mike Purvis. “But the sculptor pointed out that this is not a form you find in nature. What you actually have is spiral phyllotaxis, which follows the Fibonacci sequence – it creates the shape of a snail’s shell, for instance.”
So spiral phyllotaxis it was. “They presented the concept to us, and we instantly said ‘that’s it’,” said Elworthy.
It was then down to the engineers to translate the concept into a structure. This entailed some botanical research, homing in particularly on the spiral phyllotaxic geometry of the head of a sunflower. “We found that the structure would actually work better than the two opposing spirals,” said Purvis. “The load paths were much more efficient.”
When it came to the material, the discussions led quite naturally to timber and, for the frame, glulam. Steel girders wouldn’t have satisfied Eden’s eco criteria and didn’t seem appropriate for a building representing plant form. “Sustainability lay at the heart of the project,” said Purvis. “The brief was for a ‘symbolic building reflecting plant growth and nature’.”
UK companies were approached to provide the beams but the scale and complexity made it a big ask and eventually the designers turned to potential suppliers in Germany, Austria and Switzerland. “’My last port of call was Häring, a Swiss company,” said Elworthy. “They took us to see a health spa they’d built with a roof that moved every which way. It blew us away and showed they had the technical ability.”
It was the partnership of Swiss know-how and the “brilliant engineering” of Purvis that enabled the roof to be built, he said. The glulam supplier’s entrepreneurial owner, Chris Häring, also reminded Elworthy of his boss, Tim Smit. “Chris has this attitude that ‘anything is possible’. A lot of people have built glulam buildings but not with this double curvature, and they built them in smaller sections so they didn’t have this sweeping feeling, this integrity.”
At one stage it looked as though the stylistic ambitions for the Core might prove more than Eden’s budget could chew, with a several million pound overspend in prospect. A little value engineering was called for, but the pricey roof was off-limits.
“Everyone agreed that the aesthetic came first,” said Purvis. á Ü “To get the cost down we had another look at the engineering and decided to decided to replace the external timber buttressing with an internal ring beam of 64mm diameter Macalloy tension bars. This runs under the roof round the column heads at the perimeter of the building.”
All 330 sections of glulam were manufactured in Switzerland and assembled on site. With winter setting in, every beam had to be wrapped to prevent staining, which initially slowed progress. To erect the frame, Häring sent over six engineers and recruited another six locally.
Each roof beam spans two bays and they interlock in a shoelace grid, with the final spans to the ring beam stretching up to 27m. The calculations were challenging, but SKM Anthony Hunt made sure it kept ultimate control of the project. “We passed final design of the roof to the contractor as we knew that they would want to use the connectors they were used to and that meant we couldn’t fix the final design loads,” said Purvis. “At the same time we said this is the geometry you have to work to. As a result the design of the building wasn’t compromised. We just ended up using 820x 220mm glulam, instead of the 800x200 originally specified.”
The roof and wall panels were also constructed by Häring in sections, with the insulation fibre based on recycled paper.
Elsewhere in the building, timber and engineered wood also figured strongly. The windows, for instance, are from Scandinavian Window Systems, which use FSC-approved
laminated timber and low-emissivity glass. The bulk of the internal joinery is English oak, but floors use a mix of materials: recycled French oak in the café; recycled concrete and granite setts for the load-bearing floors in the exhibition space. The upper floors rest on a Posi-Joist system from MiTek (see panel).
“We’re trying to illustrate different materials in different places,” said Elworthy. Hence the use of lino for some of the flooring, and an “experimental” carpet made from cornstarch.
Overall, he maintained, The Core has turned out a triumphant balance of aesthetics, environmental issues and function. The design team found solutions to every practical issue, and compromises were minor. “With most buildings you have to change something,” he said. “The thing I’m most pleased with is that we managed to hang on to core principles.”
