Specific enclosures within the envelope are air conditioned, but the open circulation areas are environmentally tempered, with target temperatures of +14 degrees Celsius in winter and +29 degrees in summer. Low-level jets direct cool air across the space, while vents at the apex induce natural stack-effect ventilation. The challenge in winter is to prevent ice forming on the inside of the envelope. This is achieved by a combination of temperature control and directing warm air currents up the inner fabric surface, a strategy that also prevents downdraughts.