Greenhouses generally hold large moisture content--or condensation--needed to promote plant growth. However, too much moisture can stunt plant growth, especially plants that require less heat and humidity. high moisture content can promote fungi and bacterial growth and can encourage pest infestations, all of which can irreversibly damage plants. The Ohio State University Extension service suggests that a drier greenhouse environment is a powerful defense against plant diseases. One way to efficiently and safely remove high amounts of moisture from a greenhouse would be to install quality dehumidifiers.
Place between two and four dehumidifier units throughout the greenhouse and between eight to 10 if the greenhouse is large, near windows, doors and even tropical plants--areas where moisture is the highest. Set the dehumidifier on a block so that it sits above ground, efficiently able to remove moisture from the room.
Operate the dehumidifier throughout the day, turning it off at least three to four times at 30 minute intervals to keep it from overheating. At rest, empty its water trap out to keep the unit from getting clogged up, and from putting moisture back into the greenhouse.
Open all greenhouse windows and doors for 10 to 15 minutes during the night as the dehumidifier runs to absorb most of the moisture before exhausting it outside. Fresh oxygen from outside will circulate inside the greenhouse and cool its indoor air.