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Key to the design was maximizing natural light. Eyre explains: "This meant we couldn't use normal mullions. A 2.4-inch (60-millimeter) mullion, for example, reduces light transmission by 5 percent, whereas the silicon joints we used obscured just 1.5 percent."

In addition, low-iron glass light transmission is high — 90 percent — an increase from the 80 percent for conventional glass. With the structural engineers Dewhurst Macfarlane and Partners, the architects devised a frameless system of glass cladding, creating a virtually all-transparent surface with glass panes supported by stainless steel rods and clamps.

The structure is made of two twin-arched elements placed back to back. Due to the small footprint of the building, 1550 square feet (144 square meters), this arch geometry results in considerable height, effectively encouraging natural air movement.

The Alpine House is an ideal demonstration of effective stack and cross ventilation. Each half of the structure is, in effect, a truss, formed from an upper and lower arch, spanned by stainless steel tension rods that anchor in the base and transfer loads to the concrete retaining wall.

The rods also contribute to the daylighting by minimizing the depth and width of the cladding support. A central glazed spine and intermediate cross-spanning structure run along the length of the building between the twin trusses. This spine has opening lights for ventilation in its middle section and tilted opening vents in its sidewalls.

The rockwork inside the new Alpine House is Sussex sandstone and was salvaged from its predecessor building. Within the new conservatory, a range of habitats has been created, from broad planting bays and gullies, to narrow cracks and crevices.

There have been alpine houses at Kew since 1887. This new one, for the first time not only provides a suitable environment for the sensitive plants, but is an example of truly innovative, sustainable design and engineering.

Don Barker is a freelance writer and photographer in London, who has lived and worked in Europe, Australia, Thailand, Sri Lanka, Hong Kong, and Singapore. He is a contributing editor to ArchitectureWeek and writes for several periodicals in the United Kingdom.

Architects: Wilkinson Eyre Architects
Glasshouse Engineer: Greenmark International
Building Services: Atelier 10
Structural Engineer: Dewhurst Macfarlane and Partners
Quantity Surveyor: Fanshawe
Steel & Glass Contractor: Tuchschmid Constructa AG
Ground-works Contractor: Kilby and Gayford

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The new Davies Alpine House at the Kew Gardens, by Wilkinson Eyre Architects. Photo: Don Barker Foundation detail. Photo: Don Barker Piping cold air to the alpine plants. Photo: Don Barker Glazing detail. Wilkinson Eyre Architects Arch hub detail. Photo: Don Barker Glass joint detail with stainless steel rods and clamps. Photo: Don Barker   Click on thumbnail images to view full-size pictures.