The tropical greenhouse in the Aarhus Botanical Gardens in Denmark resembles a snail’s shell, constructed in 1969 to allow the greatest interior volume with the lowest possible surface area. The recent greenhouse renovation, designed by C.F. MÃ¸ller Architects, included an ETFE cover system planned and designed by FormTL, Radolfzell, Germany, with 3-D modeling software to precisely configure the cover over the irregularly shaped roof.
The support structure for the roof consists of 10 steel arches that fan out around a longitudinal and a transverse axis, creating a net of rectangles of varying sizes. Over these arches, FormTL installed foils with profiles bent to conform to the roof arches and double-layered ETFE cushions—except on the south-facing side, where the cushions are three-layered. Through changes in air pressure, the foils can be adjusted to increase or decrease the translucence of the cushions, changing the light and heat input from the outdoors. The inner layer of the triple cushions can be moved. “If the roof is not shaded, air can flow between the spaces to dry the cushions,” says Manuel Neidhart, project engineer for FormTL. The dual air pressure hoses don’t touch the cushions, preventing friction between tube system and cushion.