- Stack ventilation is a passive cooling strategy that relies on warm air rising and being replaced by cooler ambient air. It creates natural air currents with warm air evacuating through a high point and cooler outdoor air entering at a lower level. - For the system to function properly, the indoor-outdoor air temperature difference needs to be at least 1.7 degrees Celsius. A greater temperature difference provides more effective air circulation and cooling. - Increasing the height of a stack or using solar energy to heat the air in the stack can both increase the temperature difference between entering and exiting air.