Information on Poly Greenhouse Covering

Types of Construction

• A greenhouse made of glass is not as satisfactory as one constructed with a polycarbonate exterior. Glass doesn't diffuse light, so whitewash paint must be applied to the outside of the greenhouse. Glass doesn't insulate well and makes it difficult to keep the greenhouse warm in cold climates. Glass is difficult to install and more expensive with breakage being a constant problem. Polycarbonate provides excellent insulation and is available in various sized sheets and rolls. It diffuses light, is easier to install and is often used as end panels in greenhouses made of other materials.

Sizes and Forms

• Polycarbonate film is available in rolls of 4 to 10 feet wide with thickness up to 4 inches. There also are polycarbonate panels, plastic sheets or corrugated sheets in sizes from 6 mm twin wall, triple wall, five wall and 16mm twin wall. Sheet thickness ranges from a quarter inch to an inch, and there are several different sizes, with widths of 48 and 27 inches by 8 feet in length. Thicker sheets conserve more greenhouse heat.

UV Block and Improved Light Diffusion

• Ultraviolet, or UV, light can deteriorate a greenhouse's exterior, but poly film blocks this harmful effect and extends its useful life. If the greenhouse exterior is well-maintained and a shade cloth is used to protect it during the peak hours of sunshine, poly film will last a long time. Diffusion allows beneficial red light to pass through to promote plant growth and reduces shadows. It prevents plants from overheating and getting burnt while reducing the need for irrigation.

Heat Conservation and Improved Insulation

• Polycarbonate reduces heat loss and it's less expensive than regular glass. The thicker the poly film is, the better it is at reducing heat loss in colder climates. The film acts as a thermal window and keeps the greenhouse temperature even, providing a good growing condition for plants. During the winter, an additional sheet of poly film can be clipped to the inside walls of the greenhouse to create an insulating barrier.

Tough, Durable Material

• Polycarbonate film and sheets resist damage from hail, rocks and thrown objects. It can handle a heavy snow load or the weight of fallen tree branches. It tolerates greenhouse chemicals and some brands contain an additive to disperse condensation.

Easy to Use

• Poly film or sheets are attached to the greenhouse frame with poly clips or channels. It's easy to replace polycarbonate film, and it can be used on greenhouse frames or tunnels of wood, aluminum, PVC pipe or galvanized hoops. This is a cost-effective covering for large commercial greenhouses, nurseries or small family operations.