Visitors often expect a glasshouse to be hot. The Cloud Forest is the one that surprises them: 16°C by day, 11°C at night and damp enough that your glasses fog as the door closes.
That is deliberate. The plants in it come from the eastern slopes of the Andes at around two thousand metres, where it is cloudy most of the time and never warm for long. Many of the orchids only set flower buds after a run of cold nights.
Mist, vents and a cold floor
The house is misted for forty seconds every twenty minutes through nozzles in the roof. When the air passes 18°C the ridge vents open, and on bright days a shade screen draws across. The floor is unheated concrete, which helps hold the night cool well into the morning.
Warm is easy. Keeping a glasshouse cool and wet in a Cheltenham August is the hard part.
In summer the team runs the mist more often and keeps the doors shut. If you visit on a hot day, the Cloud Forest is the most comfortable room in the garden.