We are developing a new 300m² Galapagos Tortoise Exhibit at ZSL London Zoo.
The planting scheme consists of a range of tropical trees and shrubs, such as
Coccoloba uvifera, Plinia cauliflora, Eugenia uniflora, and Calliandra
For similar previous projects, we have installed ETFE as roof material, which
has a proven track record in terms of light transmission and spectral range.
The principal contractor for this project proposes using a bespoke fabric
called Opal 60 to save costs. The material is mainly used in trade environments
such as garden centres. According to a datasheet it reduces transmission to
48% and UV-T to 4%. What's more, the marketing material states that the
material cuts out UVA and UVB rays.
The same contractor replaced the polyethene skin on the Butterfly Exhibit at
ZSL Whipsnade Zoo with a mix of Opal 60 and ETFE (the initial proposal had been
to use Opal 60 only). As we came into autumn, the impact was that most of the
nectar plants, such as Lantana camara and Pentas lanceolata, and some of the
larger trees either died or displayed severe dieback. Interestingly, the
observed impact coincided spatially with the Opal 60 and ETFE strips of the
Based on the available technical data for Opal 60 and our experience at
Whipsnade, I believe the material is not suitable for growing tropical plants
in a protected environment.
At the same time, there is still a desire to achieve cost savings. I have been
asked to evaluate a sample of the material to assess its properties rather than
the manufacturer providing proof that it works for the intended purpose.
I'm aware of a basic range of lux values used to describe low, medium, and high
light level requirements of indoor plants.
Does anyone have knowledge of more technical information or would be happy to
share their experiences (good and bad) with roof materials in tropical exhibits?
Curator of Plants
Zoological Society of London
Chair BIAZA Plant Working Group
Co-chair EAZA Zoo Horticulture
London NW1 4RY
t: +44 (0)20 7449 6521
m: +44 (0)7812 235598
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