Relative humidity

• Green house is a closed space, the relative humidity of the greenhouse air will be more when compared to the ambient air, due to the moisture added by the evapo-transpiration process.
• Ventilation and heating systems controls RH.
• Humidification or dehumidification are carried out.
• For most crops, the acceptable range of relative humidity is between 50 to 80%.
• However for plant propagation work, relative humidity up to 90% may be desirable.
• In summer, due to sensible heat addition in the daytime, and in winters for increasing the nighttime temperatures of the greenhouse air, more sensible heat is added causing a reduction in the relative humidity of the air
• For this purpose, evaporative cooling pads and fogging system of humidification are employed.
• When the relative humidity is on the higher side, ventilators, chemical dehumidifiers and cooling coils are used for de- humidification.