Avoiding condensation in glasshouses

Find out how identify and manage the risk of condensation in your greenhouse crop.

Avoiding condensation on plants is a key part of any disease control strategy. Poinsettia growers have to pay particular attention to this problem as they use a technique to control plant height called ‘Drop’. ‘Drop’ involves reducing the greenhouse temperature to as low as 12^oC before sunrise and is followed by an increase in the greenhouse temperature to the daytime set point within one hour after sunrise.

The risk of condensation is greatest during the period when the greenhouse temperature is increased; if the plants do not warm up as quickly as the surrounding air, condensation can occur. In practice this is a common problem as cold air can be trapped within the crop canopy causing the plant temperature to stay lower than the air above it. The warm air above the crop comes into contact with the cold plant and moisture is released.

Similar problems can occur with all crops, so the techniques described are universally applicable no matter what you grow.

The plant temperature should never be lower than the dew-point of the air in the glasshouse. You can take direct measurements from the plant or use a computer model to predict the temperature and help avoid condensation. Read on to learn more.

Read about the relationship between glasshouse temperature, calculated plant temperature and dew point temperature and the reasons for high condensation risk.