Greenhouse Condensation Control

Written by thomas king
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Greenhouse Condensation Control
The amount of moisture in the air is expressed as relative humidity (RH). (condensation image by John Keith from

A greenhouse is a structure, generally made of glass, designed for the cultivation or protection of plants. One of the most critical tasks in greenhouse maintenance is controlling condensation.

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Condensation refers to the formation of liquid drops of water from water vapour. In greenhouses, condensation generally appears on plants and greenhouse coverings. Condensation is a symptom of high humidity and can lead to significant problems, including germination of fungal pathogen spores, including Botrytis and powdery mildew. Moreover, condensation that forms on the greenhouse covering can fall and spread plant pathogens from plant to plant by splashing soil and plant debris.


Plant surfaces must be kept above the dew point to avoid condensation. To do this, install a heating distribution system near or below the plants. There are several heating systems available. Pipe heating is perhaps the most common and involves installing a network of metal or plastic pipes that distribute hot water. Pipes are most effective when placed between the middle and bottom of the plant. Warm floor heating provides heat through a hot water system below the soil or below the concrete floor surface. One of the main advantages of warm floor heating is that the heat rises, which provides better air circulation than some heating systems. Finally, air heating refers to a system of heating that uses forced air heaters placed overhead, with heat distributed via fans.

Air Circulation

Improving air circulation will reduce condensation by evaporating the condensation. Improved air circulation is generally achieved using horizontal air flow fans or a perforated poly tube system. These tools should be used in combination with proper ventilation. Air circulation can also be improved by using open mesh or slatted benches, as opposed to solid benches, and increasing the space between plants.

Measuring Humidity

Part of condensation control involves knowing the humidity inside your greenhouse. Humidity can be measured using a sling psychrometer. Psychrometers are available at most greenhouse supply and scientific equipment stores. Humidity pocket meters and humidity pens are also available and are generally cheaper than psychrometers. Ideal humidity levels will differ depending on specific climate conditions and plants.

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