The Great Glasshouse
* The Great Glasshouse (GGH) is the focal point of the National Botanic Garden of Wales.
* It is an elliptical torus, 95 metres long and 55 metres wide.
The domed roof is made up of 785 glass panes. Most are approx. 4 metres by 1 ½ metres in dimension. One hundred and forty seven can be opened using actuators. The glass panes are 18mm thick and are made up of two pieces of glass sandwiched together with a laminated film. Each piece took two weeks to make. There are 4500 square metres of glass.
* Twenty-four tubular arches are attached to the concrete plinth using a steel ball and socket joint. The joints allow the steel ribs to expand without transferring stresses to the glass or the concrete.
* Influential in the design of the GGH was the history of the Middleton Hall estate and the topography of the land. The intention was to create an interior space which related both to the historic landscape still in evidence around the GGH and to its rural setting.
* The sweep of the dome and its steel arches on an inclined rather than vertical plane, creates not only a dynamic effect, it also corresponds to the local contours of the surrounding hills. Thus the sides of the GGH are fully integrated into the landscape and the dome appears to grow naturally out of the valley.
* The sod cutting ceremony took place in June 1997 led by Councillor Howard Jones, Chairman of Carmarthenshire County Council, and David Baird from the Millennium Commission. In October work began on the concrete structure. In December the Right Hon. Ron Davies MP, Secretary of State for Wales, and Eric Sorenson, Chief Executive of the Millennium Commission, buried a time capsule within the foundations of the Glasshouse. Work began on the steel structure in May 1998. In June 1998 the `topping out` ceremony took place and the glass panels began to be put in place. The last pane of glass was put into place on October 5th.
* The geometry of the design was so complex that it was not put down on paper but on computer and put into practice using high precision electronic distance measuring equipment.
* The thermal regime in the GGH responds to the availability of heat from the sun and seeks to store excess heat within the ground for release at night.
The GGH will enclose one macro-climate with slight variations. The micro-climates are created by shade from trees or rock faces and local variation of heat and ventilation.
* Natural ventilation is not only a prerequisite for the Mediterranean climate plants housed within, it also satisfies environmental and economic conditions. The climate inside the GGH are regulated by 147 computer-controlled vents. The glazing system allows for a fully controllable and natural flow of air to strengthen the plants and remove excess humidity and heat. The computers that control this movement will be alerted to any changes in the weather via an electronic link with a local meteorological centre. The central biomass wood chip boiler provides heat for the avoidance of frost in winter.
• Rainwater will be collected on the site. Each of the 785 panes of glass making up the roof of the GGH is designed to channel rain into two 70,000 litre tanks. This water will then be pumped out for use inside the GGH itself for irrigation and for flushing lavatories. Since the natural rainfall of the site may not always meet the water requirement for irrigation during a dry summer, borehole water, in preference to the use of portable mains water, will be extracted.
* At the heart of the project is a natural philosophy: the whole life-cycle of the energy supply system components minimise use of resources. The structure of the building responds to changing environmental conditions; this contributes to the energy efficiency of the scheme.
* The interior landscape was designed by Gustafson Porter and measures 3500 square metres. It houses threatened plant species found in Mediterranean climates from the Cape region of South Africa; South Western Australia; Chile; California, and the Mediterranean basin in Europe.
The key to the project’s success is to attempt to create a coherent landscape within a building. As one enters, the eye is drawn down into the ravine (reaching a depth of 6 metres), and the perception is of a landscape parted from the building. The roof becomes the sky that holds the landscape within it. Gentle rock terraces accompany the movement of the ground down to the ‘shear walls’, as the landscape pulls down into a narrow gorge bordered by water.
The ground plane is finished in crushed gravel scree of varying coarseness from a light-coloured sandstone to match that of the rock faces. The garden becomes a landscape, and people are free to move over much of the ground surface either side of the main routes.
Planting follows a concept unused in other Botanic Gardens; it is based on form, density, and colour and not exclusively plant type or regions of the world. The visitor still moves from country to country, but always within the sensation of an integrated environment.
* Bioverse is an interactive educational exhibition housed in the Great Glasshouse, explaining the importance of plant life and mankind’s dependence on it. Buried in the north wall, Bioverse leads the visitor through the life cycle of a giant plant using video techniques and computer graphics.
