Greenhouse Evaporative Cooling
If ventilation and shading are not sufficient, greenhouse temperatures can be controlled by means of evaporative cooling, also referred to as swamp cooling.
When water evaporates in the air, energy is needed. This energy comes from heat, which is dissipated from the hot air. The more water can evaporate in the air, the more heat is dissipated and thus the more the greenhouse is cooled. The initial temperature and the initial relative humidity of the air determine how much water can be evaporated and thus what the cooling capacity is and how much the greenhouse temperature can drop.