(continued)

The idea of the Eden Project was simple: to create a world-class tourist destination that would tell the story of humankind's relationship with plants. Visually it had to provide a spectacular theater high enough to house the towering trees of the rainforests, wide enough for the sun-baked escarpments of the Mediterranean and, oh yes, become the eighth wonder of the world. Easy!?

The Site

A deep clay pit just outside St. Austell was ideal for the project because it provided protection from the wind and had a large south-facing cliff, ideal for sunlight.

The idea was to erect large "conservatories," or greenhouses, on the south-facing slopes, where the clay on the back wall would provide a natural solar collector and storage system providing a 24-hour heat bank. The north-facing slopes would provide a plethora of stepped plantations with sculptural representations.

However, the site was not perfect. Its cone shape made it prone to flooding, it had no soil, and it was unstable. These problems were seen by architects, engineers, and horticulturists alike as "opportunities" rather than major obstacles, such was the enthusiasm within the project team.

The Design

The overall concept was to create an experience that would fill the visitor with anticipation, excitement, and amazement — landscape and architecture conceived as one.

According to Land Use Consultants, the landscape architects and the master planners for the site, "Everything from the way visitors arrive on site, park their car, enter the pit, and explore the buildings has been designed to provide an experience of unraveling landscapes."

The stories of human dependence on plants was worked into the shaping of the site with the help of artists and sculptors. "Tags on plants was considered not good enough."

There were to be two indoor environments, one for humid tropics and the other to house a warm temperate climate, along with the extensive outdoor garden for cool temperate plants.

The indoor structures were to be giant conservatories called "biomes," which would be built on the side of the south-facing slopes of the clay pit, providing a natural presentation arena for the plants.

The software used for the terrain modeling was Inroads by Bentley Systems.

Initially it was envisaged that the two biomes would be constructed of glass and steel and modeled on the roof of the International Terminal at Waterloo in London. Therefore the terminal's architect, Nicholas Grimshaw and Partners, was approached for ideas.

The practicalities of giant support trusses proved to be prohibitive partly due to their blocking of natural light. This would result in the plants growing unnaturally in their efforts to catch as much sun as possible.

Space frame specialist Mero (UK) had an alternative solution: the geodesic principle, which involves joining together flat surfaces to form a curved shape. A geodesic line is the shortest distance between two points on a curved surface and provides the platform for true freeform architecture.

The patent owner of the geodesic dome was American Richard Buckminster Fuller, whose largest dome was the U.S. Pavilion at Expo '67 in Montreal with a 250-foot (76-meter) diameter.

Mero (UK), Nicholas Grimshaw and Partners, and structural engineer Anthony Hunt Associates worked together to develop a series of intersecting domes. They realized that glass was too heavy, inflexible, and dangerous for this application and that ethyltetrafluoroethylene (ETFE), a strain of fluoropolymer, provided the solution.

As well as being strong, lightweight (it weighs one percent of the equivalent sized glass panel), and highly transparent to ultraviolet light, ETFE is not degraded by sunlight, has better insulation properties than glass, is recyclable, and can support 400 times its own weight.

Although it is susceptible to punctures, it can be patched by using ETFE tape. ETFE foil has been in place at Burgers Zoo in Holland for over 20 years. The decision was made; the biomes would be clad with 6.5-foot (2-meter) deep inflated cushions made up of three to four layers of ETFE.

The Biomes

Each biome comprises four domes, strengthened by steel arches where they intersect. The shape provides maximum size and strength, using minimum steel and hugging the contours of the clay pit's varying contours. Collectively, they are the largest greenhouses in the world. The larger biome — the humid tropics — covers 170,000 square feet (15,590 square meters) or 3.8 acres (1.55 hectares) and is 180 feet (55 meters high), 330 feet (100 meters) wide and 660 feet (200 meters) long.

The warm temperate biome is 70,000 square feet (6,540 square meters) or 1.6 acres (0.65 hectares) in area, 115 feet (35 meters) high, 213 feet (65 meters) wide, and 440 feet (135 meters) long.

The hexagons, pentagons, and triangles that make up the biomes all have their own unique specification due to the irregular nature of the site. The biome frame analysis was carried out on STAAD III software by Research Engineers.

Mero's computer-simulated models, sent via e-mail to the company's fabrication shop in Germany, controlled the milling equipment, ensuring that individual sections were cut to exact length and specifications with zero tolerance.

To further strengthen the hexagons, separate diagonals connect the node points of the layers together. This structure, the first of its kind on this scale in the world, is called the "hex-tri-hex."

Heating is provided from large fan heaters, which are supplied with hot water by an underground heating main. The direction, strength, humidity, and temperature of the airflow is controlled by computer software. It controls the openings at the top and bottom of the domes. Hot air is dispersed via the top and replacement cooler air is drawn in at the bottom.

The Tuscany-like lunar landscape of the Eden Project. Photo: Don Barker Inside the humid tropics biome. Photo: Don Barker Inside the warm temperate biome. Photo: Don Barker Overview of the Eden Project. Image: Land Use Consultants Side elevation of both biomes showing how the domes connect to form two giant biomes. Image: Nicholas Grimshaw and Partners "The Link." Photo: Don Barker Cross section of the humid tropics biome. Image: Anthony Hunt Associates Computer model of overall site. Image: Anthony Hunt Associates   Click on thumbnail images to view full-size pictures.