02.10.2010
Utilizing mathematical sequences and geometries found in nature, a new building for Eden Project uses architecture, pattern and light to underpin the messages taught within.
This article was originally published in Blue 02: Systems and Structure in 2010. You can see the article in its original format, and other articles, online.
The Core is a purpose-built education building at the Eden Project in Cornwall. It was conceived to help convey Eden’s central message about the relationship between mankind and the natural world around us, with a particular focus on plants. The resulting design connects mathematical formulae, natural systems for efficient growth in plants, and a geometry that resonates throughout the organic and inorganic world.
The defining feature of the building is a roof that spans from a central ring of supports over all of the main spaces within the building, including an exhibition space, classrooms, a cafeteria and offices. Visible from all key areas of the building, this roof offered an opportunity to ‘speak’ to everyone who passes through. It does so through the incorporation of a geometry found in the system of plant growth known as spiral phyllotaxis, in which a number of spirals radiate in two directions to form a grid. Many plants demonstrate this growth pattern, which accommodates the maximum number of seed heads to grow sequentially in a given area: an example of highly efficient ‘packing’.
This geometry was explored with Peter Randall-Page, a sculptor who became an intrinsic part of our design team. With many years of experience in the study and interpretation of natural geometries and forms in his own sculptural work, Peter became an invaluable collaborator, opening our eyes to the possibilities of spiral phyllotaxis in our design. As one of the archetypal natural patterns, we felt that this geometry could form the basis for the roof of the Core in such a way that it could be explained to all visitors, but that it would also communicate more implicitly something of the inherent ‘rightness’ of a pattern that has evolved over millennia. Early incarnations of our design intuitively used a symmetrical approach to the geometry, with an equal number of spirals in each direction, and this was proving very inefficient in structural terms. Peter helped us to understand the natural occurrences of the pattern, and the strict mathematical rules that underpin it.
Interestingly, this organic pattern relates to a system of proportion used by artists and architects for hundreds of years. Examination of all examples of spiral phyllotaxis in nature reveals that the numbers of spirals radiating clockwise and anti-clockwise are always two consecutive numbers from the Fibonacci numerical sequence. This sequence, first postulated by Leonardo da Pisa (or Fibonacci, as he was nicknamed), is such that the next consecutive number is the sum of the two previous numbers: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, etc. The ratio between each consecutive pair of numbers tends to 0.618, or ‘phi’, otherwise known as the Golden Ratio, and informs the ‘Golden Section’ proportion used by architects from Vitruvius to Le Corbusier and beyond.
With a more detailed understanding of the pattern, we
redesigned our grid, hoping that some of nature’s efficiency would also help
our roof structure. For the roof of the Core, a geometry was established with a
grid of 21 and 34 spirals, developed with Mike Purvis, a structural engineer
with SKM. His enthusiasm and technical expertise led to a roof structure that
could be efficiently constructed using laminated timber. To our delight Mike’s
calculations, based on nature’s formula, showed that the problem had been
solved.
Such a complex geometry led to a whole range of interesting design challenges before the roof could be realised, some of which are described here by Andrew Thomas. The process of sourcing and building the roof is described by Jerry Tate. Whilst the geometry of the roof is described here, many other stories could be told about the building, including the passive air heating and cooling, the first sustainable certification of the copper roof cladding, and the incorporation of arts and interpretive material within the fabric of the building (not least the installation of Peter Randall-Page’s sculpture, ‘Seed’, at the heart of the building, carrying the same phyllotactic pattern across its surface of undulating granite).
The result of all of this work was a building that fulfilled all of the functional requirements for the Eden Project’s educational facility. Just as important has been the incorporation of botanical imagery in a contemporary and meaningful way, in the very structure of the building. This has answered one of the client’s key requirements: to take the message of our dependency on plants to a deeper level.
Take a toroidal surface and project two countervailing spiral grids vertically through it: the underlying geometry of the Core’s roof is a relatively simple thing. Once the project’s resident structural engineer, enthusiast of advanced maths and all-round Renaissance Man, Mike Purvis, had written his ‘Phyllotactic Generator’ (a piece of software which calculated the precise co-ordinates of our spiral grid), the building geometry could be modelled in three dimensions with no more than a few dozen clicks of the mouse.
Developing the form of the roof’s upper surface was much more time-consuming, but still relatively straightforward. Following the biomimetic theme, there was a very clear concept for an array of overlapping ‘leaves’, echoing the roof’s spiral geometry, not unlike the leaves of an artichoke. Through a series of physical models, we developed some simple rules around the practicalities of turning a flattened-out artichoke into a water-shedding roof. Coming before the advent of parametric modelling (at least for the author!), the final geometry of the roof could only be developed through individual modelling, testing and adjustment of each roof panel until each ‘leaf’ obeyed all of these rules.
By the time our Swiss timber specialists, Haring, joined the team, the building geometry was set, along with some quite well-defined proposals for its fabrication. In the months that followed, the relationship between the design team and Haring provided a clear illustration of the value of open collaborative working, as Haring brought their expert knowledge of material performance, fabrication and construction to the team. The apparent simplicity of the process described above belied some areas of significant hidden complexity, once the limitations of technology – and budget – were understood fully. Responsible for the full extent of the building’s timber structure and envelope, Haring contributed significant ‘Eureka’ moments throughout the detail design; however, one moment, detailed below, is particularly memorable.
An immediate consequence of selecting two dissimilar spiral geometries for the building grid is that each of the cells defined by that grid is unique. While the team were quick to understand the inefficiency inherent in fabricating 190 unique roof panels, each double-curved and twisting in plane, we knew that the expression of each unique ‘leaf’ on the roof was fundamental to the building concept. In this case it was Haring who identified an elegant solution: whilst each individual cell may be unique, the roof panels could equally well be fabricated as a series of spiral ribbons, each of which would be identical. As the dialogue continued, we discovered further benefits in this strategy: both the building services and roof drainage worked most efficiently in a simple radial direction and provision for these elements could now be prefabricated into the roof panels in the factory.
As for the clear expression of the individual ‘leaves’, this could be achieved by simply extending the edge plates of the ribbons to follow the stepped profile required. The end result was a remarkably light, monocoque structure for the roof panels, prefabricated entirely from engineered timber board and transported in large modules to the Eden site.
One of the great joys of designing a large span timber gridshell roof is meeting the amazing people involved in the design, supply and manufacture of the structure. At the time of undertaking development of the roof for the Core, the timber structure expertise in the UK was more limited than today, so we looked for specialists on the continent who could help us deliver the roof in a sustainable manner. This initial ‘contractor hunt’ involved a madcap tour by train and bus around southern Germany, Austria and Switzerland with Eden, SKM Anthony Hunts, Davis Langdon and McAlpine JV. After a series of disappointing meetings we eventually met Chris Haring of Haring AG, near Basel, who (to our slight disbelief) declared that our proposed roof would be ‘no problem’; to prove it, he showed us an incredible double-curved gluelam structure he had completed at a nearby public baths. From this initial meeting we started a very fruitful design dialogue, which also provided us with an insight into Swiss methods of manufacture.
Haring AG, a family company, operates within a network of similar companies in their local region. Although not formally linked, they all have an understanding in terms of each other’s capabilities, timescales and methods. They also demonstrate a deep sense of social commitment with their relationship to the community and the environment. Sometimes this results in astounding feats unheard of in the UK; for example, Haring, in co-operation with other companies, was capable of building high quality affordable housing extremely quickly with a house taking approximately one day to assemble on site (from pre-fabricated components).
One of our more interesting visits was inspecting the supply chain for the Core’s timber structure, from timber supply to the CNC milling. Meeting the foresters was fantastic; Switzerland produces approximately 3 million tonnes of timber per annum, but only has a domestic requirement of 1 million tonnes meaning that the surplus needs to be exported. Instead of felling large sections of the forest, trees are felled with a machine which literally ‘plucks’ them individually from the ground and strips them immediately with no detrimental effect on the surrounding trees. This allows the forest to be thinned as required, without a blanket removal program. The sawmill where the timber was processed was fastidious in using every part of the tree, including the timber waste which was fed in to a district heating system that not only heated the factory but the surrounding village as well! At Haring’s factory, computer-controlled hydraulic jigs enabled the complex geometry of the roof to be translated into the double-curved laminated beams. The highlight for me, however, was the CNC milling factory where the timber components were milled to within a 1mm tolerance, before being transported to the UK and assembled on site. All of these stages of manufacture were performed at separate companies, yet all were within half an hour of each other (and generally could be reached by train, with the exception of the forest).
Timber frame manufacture in the UK is now expanding at an exponential rate to cope with our increasing demands for sustainable, low-carbon buildings. One of my most heartfelt desires is that we achieve the level of craftsmanship and social responsibility I witnessed in action in the Swiss industry.