Britain's weather conditions — with fluctuating temperatures and humidity — are considerably different from those in an alpine habitat. In an alpine greenhouse, therefore, shading, air movement, and additional light are the key ingredients.
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Most importantly, where plants are grown in a protected environment, the amount of water they receive can be controlled, giving them the conditions they need to thrive. Watering is done by hand because sprays create too-high humidity levels.
Cooling Alpine Plants
The key issues for developing the new Alpine house were creating a dry, cold growing environment for the plants and, according to Wilkinson Eyre, demonstrating "the same spirit of design innovation as seen in Kew's other notable glasshouses."
Jim Eyre, principal of Wilkinson Eyre explains their three key aims. "We wanted the new structure to attract more visitors as well as being an exacting environment for the Alpine plants. We were also keen to exploit 21st century technology."
The advanced "labyrinth" cooling system, designed with Atelier 10 environmental consulting engineers, maintains the plants in near-Alpine conditions without the need for refrigeration.
The imaginative alternative energy system uses natural cooling rather than air conditioning. Eyre says: "Our concept was for a structure that could generate cool air drawn in partly through ventilation grills around the base and escaping through the 33-foot (10-meter) roof."
Incoming air is exposed to a large surface area of concrete by passing at low velocity down a 100-foot (30-meter) tunnel beneath the structure. The walls of the tunnel are cooled by night-time air, and they in turn cool down the hot outdoor supply air in the summer. The Kew labyrinth is simply made from faceted concrete walls forming long air paths for the air to flow down.
The cool night air flushes the heat of the day out of the concrete, along with some of the moisture, so the mass is cool again for the following day. The flow of air can be controlled through the various chambers to provide some responsiveness to external conditions.
Four small low-energy fans help push the air into the building. The labyrinth maintains comfortable temperatures even when outdoor air reaches 86 degrees F (30 C). As well as cooling the glass, the cool air blows out through foghorn-like nozzles among the plants.
Having visited the building on one of the hottest days of the summer, with temperatures around 99 degrees F (37 C), I can vouch for the success of the design: cold air was still blowing out over the plants. And the system uses 90 percent less power than conventional cooling systems.
Eyre notes: "Patrick Bellew, from Atelier 10, is interested in how ants adapt their environment. Additional cooling is provided by a system akin to termite mounds, where cooler air is drawn in through an underground chamber. Termites use mud to plug or open vents to keep the core of the mound cool. We use automated flaps."
The tunnel is also used as a structural stiffener. The concrete box is much stiffer than a slab, helping to resist all structural loads.
The new building is also kept cool and shaded with the help of blinds that fan out like a peacock's tail. Using sail technology from yachts, the white polyester blinds gracefully open and close in no more than a minute. The two blinds, one for each side, work independently of each other to react to the sun's position throughout the day. The architects decided not to automate that process, leaving it to the plant experts to determine when a fan should be opened.
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