Humidifying Your Greenhouse

Humidifying Your Greenhouse

Misting Guidelines

Apply mist only during daylight hours to avoid excessive humidity at night, which encourages disease. Remember, when the greenhouse cools at night, the relative humidity will rise even with the misting system off. Use a 24-hour timer to shut off the misting system 2 hours before sundown.


Shading and ventilation are required during summer to prevent a greenhouse from seriously overheating, but it is evaporative cooling from a misting system which can actually cool the greenhouse to a comfortable level.

Humidity Control

When a greenhouse warms up and venting begins, essential moisture is lost with the vented air. Plants lose moisture more rapidly and begin to wilt. A misting system can provide needed moisture to maintain a healthy humidity level of 50 to 70%.

Design for Cooling & Humidity Control

Use one 2 or 3 gph nozzle for every 12 to 14 sq. ft. of greenhouse floor. Install nozzles under the benches to avoid soaking plants on the benches. Nozzles will operate pointed in any direction – up, down, sideways or 45° angle. Control this type of system with a humidistat.

Overhead Watering

Many foliage plants, tropicals and subtropicals can be watered and fertilized by an overhead misting system. Use 2 gph nozzles installed as high as possible. Control this system with a short-cycle timer.

Propagation/Orchid Misting

Maintain a higher level of humidity (60 to 70%) for healthier plants. Protect seedlings and cuttings from fatal water stress. Imitate orchid’s natural environment. Use 1 gph nozzles. Control with a short-cycle timer: 5 to 10 seconds of mist every 15 to 30 minutes.

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