Excess moisture is bad for the plants in your greenhouse and may cause fungus-based plant diseases if left untreated. When removing condensation from greenhouse windows, you have both long-term and short-term control methods. If condensation is a chronic problem in your greenhouse, providing additional sources of dry heat can help remove some of the moisture.
Remove any excess sources of water that you have in your greenhouse, such as barrels of water. Turn off any drip irrigation or mist systems. You can turn them back on once you have cut back the moisture level in your greenhouse.
Open the windows or the door to your greenhouse and allow excess moisture to escape.
Turn on your greenhouse fan, if you have a fan. This will improve the air circulation and will drive the excess moisture out of your greenhouse. If you do not have a greenhouse fan installed, you can plug in a fan and place it on the floor inside your greenhouse.
Shut the door or the windows after some time has passed. In cold weather, you may want to leave them open for only 10 to 30 minutes to prevent the temperature from dropping too much. In warmer weather, the fresh air will be beneficial, so you don't need to be as concerned about time limits.
Purchase a humidity controller or a dehumidifier for use in your greenhouse. This will remove excess condensation. Portable dehumidifiers work well in portable greenhouses or small greenhouse environments.
Monitor the moisture in your greenhouse. When you can shut the windows or door and no new condensation appears on the greenhouse windows, you may turn off the fan or humidity controller.