Polyethylene Sheeting has been used in greenhouses since the early 1960’s, because it is an efficient alternative to some of the pre-manufactured options. Greenhouse poly film has evolved over the years to address many of the concerns in greenhouse applications such as the life of the film, the thickness/durability, condensation control, heat gain/loss, UV and light transmission, etc.
Most of these features are not found in the cheap poly you buy off the shelf at your local hardware store, so determining your budget will help you pick out which cover is best for your greenhouse. Below are some things to think about when you are ready to purchase a greenhouse cover.
1. How often can you afford to change your cover?
The longevity of a greenhouse cover can vary from 1-4 years and sometimes longer. Sunlight and heat exposure causes polyethylene film to degrade over time so ultraviolet stabilizers are added to reduce that effect. Wind can also cause wear and tear, in which case a scrim reinforced poly or woven poly would provide additional durability.
2. How thick should you get the cover?
Mil thickness measures how thick the cover is and can affect how long your greenhouse cover lasts. The thicker the cover, the more durable it will be, but it will also be heavier. Polyethylene film is available in 3, 4, 6, 10, 12, and even 20 mil thicknesses. Most 3-4 mil poly films last a year. A minimum of 6 mils is suggested for outdoor greenhouses and they can last at least 3-4 years, sometimes longer. A reinforced greenhouse cover can be measured on the scrim or the plastic sheeting itself depending on who is measuring it. If it’s measured by the scrim, the plastic sheeting could be much thinner than indicated.
3. What type of panel clarity should you use?
Greenhouse covers can be clear, translucent or opaque and are available with or without diffusion. A clear covering will deliver full, direct sunlight providing more warmth, which is good if you want to germinate seeds and grow starters. The heat generated will help develop starter plants for transplanting.
An opaque panel diffuses light so it reaches the plants in many angles. This is ideal for maturing plants because it helps to prevent hot spots and provides a balanced structure instead of the plants leaning towards available light.
There are also semi-diffused greenhouse covers that offer the benefits of a clear with light diffusion, and sometimes a clear is applied to the roof, with a diffused liner on the sides.
4. Do you need Condensation Control?
Anti-drip or anti-condensate prevents droplets from forming and allows the water to flow down. If condensation builds up it can reduce light transmission as well as drip into the plants causing them to get diseases. Some greenhouse covers are manufactured with this additive, but you can also purchase an anti-fogging spray.
5. Is the Plastic Sheeting Bee Compatible?
UV light is important to a grower using bees to pollinate plants because it makes it easier for them to navigate, but it also extends the life of the cover, can reduce whiteflies, aphids and other insects as well as prevent some fungal diseases.
6. Reinforced or Non-reinforced?
Without reinforcement once plastic sheeting starts to tear or rip, it will continue to do so until you replace it. A scrim reinforced greenhouse cover will stop a hole from becoming larger and is much easier to salvage with tape. Areas that have a lot of wind, rain and snow would benefit from a reinforced cover.
7. Do you need heat insulation?
Most polyethylene sheeting for greenhouses will insulate heat to some degree, but films that contain infrared additives trap the radiant heat in causing less heat loss. As a result you save money on energy costs because you don’t have to run the heaters as long. Often times this is installed inside the greenhouse as a double layer to keep heat in at night when it cools down outside or in cold weather climates. Double layering is common among greenhouses to keep heat inside the greenhouse
8. Will you do light deprivation?
Light Deprivation is a 12/12 light cycle with 12 hours of light and 12 hours of dark (although there are other light dep cycles). Light deprivation tarps or covers are typically black on one side and white on the other. The black side keeps it nice and dark inside the greenhouse while the white side applied on the outside reflects the sun to keep it cooler inside. Poly sheeting for light deprivation can be reinforced, non-reinforced, and even woven coated. BOLD black out light dep covers are 100% light blocking, contains zero pinholes or perfs, reinforced for added durability and contains UV inhibitors.
There are many different products on the market for greenhouse covers and light deprivation covers that have a ton of special features. The staff at Americover is dedicated to helping you find what works for your greenhouse project and your budget. Give us a call at 800-747-6095 for more information. We also carry plastic sheeting for indoor growing!