What are greenhouse curtains?
Greenhouse curtain systems also known as greenhouse screens or greenhouse shades consist of moveable fabric or plastic films that are used to cover and uncover a greenhouse. They are used to cover either a small area of the greenhouse, that is a particular patch of certain crops or the entire greenhouse.
The movement of these greenhouse curtains can be either entirely automated (generally done for large greenhouses) or can be manually moved by hand. The main function of a curtain is to provide heat retention for the plants.
How do curtains provide heat retention for the greenhouse?
Generally, the heating demand for plants is highest at night and any greenhouse curtain can be used to meet this demand. The amount of heat retained, hence reducing fuel cost, varies based on the material of the curtain film.
Curtains can trap an insulating layer of air inside the greenhouse, reduce the volume to be heated and if the curtain has an aluminum strip, it can reflect heat back into the greenhouse.
Removal of curtain during day time:
It is extremely important to remove the curtain very slowly during the day as a curtain that is used specifically for heat retention traps the cold air between the fabric of the curtain and the roof of the greenhouse. If the curtain is opened very fast, then the cold air will drop straight on the plants, causing a sudden change in temperature and damage the plants as they wont be able to adapt to this change immediately.
To avoid this, the curtain should be uncovered gradually to allow the cold air on top to mix with the hot air already present within the greenhouse. Another option is to let the sunlight warm the cool air and then the curtain can be uncovered allowing the hot air existing inside to mix with the naturally warmed air outside. This option is however viable only if the plants can tolerate some level of shade during the day time or if artificial lighting systems are installed within the greenhouse.
Material for creating the curtains:
• Knitted white polyester
• Non- woven bonded white polyester fabric- made with alternating lines of clear and aluminum strips to reflect heat into the greenhouse.
• Composite fabric- flame resistant fabrics with gaps for air circulation
Benefits of greenhouse curtain systems:
• Helps in controlling the humidity of the greenhouse
• Heat retention during night time
• Reduces day time fluctuation of temperature
• Increases summer shading
• Cost effective compared to an artificial heating and shading system
• Can be automated completely hence reducing manual labor and labor costs
• Reduces energy consumption
• Provides conducive environment for plants even during the night time
• Day length control for exotic plants
Types of greenhouse curtain systems:
- Gutter-to-gutter curtain system- This refers to a type of system where a single panel of fabric is used for each house. Under this system, the curtains are pulled flat across the width of the greenhouse at gutter height. Here, the volume of hot air inside the greenhouse is much lesser as compared to the volume of cold air above the curtain causing difficulty in mixing the cold and hot air when the curtain is lifted during the day time.
- Truss-to-truss curtain system- This refers to a system where a curtain is present between each truss. When the curtains are moved, each section moves at the same time, speed and amount hence covering the area between the trusses
There are different kinds of greenhouse curtains that can be adjusted based on the needs of the plant and this is the quickest and most cost-effective method of trapping heat and provide shade to the plants within the greenhouse.