What is the Best Plastic Covering to Use for a Greenhouse? Our Guide to Greenhouse Plastic

Greenhouse plastic is a crucial component of any greenhouse or high tunnel setup, providing an optimal growing environment for your plants. 

Over our decades of growing and working with farmers around the world, we’ve learned that the best greenhouse plastic really depends on your specific set up and needs. In this comprehensive guide, we will delve into the different types of greenhouse plastics available, their features, and how to determine the best option for your greenhouse. Additionally, we will cover some essential tools and installation tips to help you make the most of your greenhouse investment.

Photo by [Lisa Knoebel Photography]

Introduction to Greenhouse Plastics: Woven Vs Regular

It can be overwhelming to think about which greenhouse plastic you should choose. Fear not, we’re here to make it as easy as possible. First, let’s break down the difference between Woven plastic and Regular plastic. 

Our 6 Mil Clear Polyethylene Greenhouse Plastic and High Diffusion 6 Mil Open UV Greenhouse Plastic are both types of regular greenhouse plastic. They are high-quality and great choices for many growing scenarios.

If you’re looking for extra durability, or live in an area with frequent thunderstorms and hail, you may want to consider a woven greenhouse plastic. Woven plastic (available in 8 mil and 11 mil) has a few features that make it stand out. 

First off, the strength factor. Woven is incredibly strong and puncture resistant. It withstands hail and flying debris very well.

Woven also has two sides - a matte side and shiny side. This is great because you can get two different levels of diffusion out of it. Depending which way you put it on you can get 60% or 30% diffusion. You’ll want to choose which side you use based on your location and what you’re growing.

It’s worth noting that you may need a different lock channel for installing woven greenhouse plastic. This is especially true if you’re using insect netting and roll up sides. The thick 11 mil takes up more space in the lock channel, so you may need to go with a double or deep lock channel depending on the design of your greenhouse. Feel free to reach out to our tech department if you have questions on installing woven greenhouse plastic on your existing structure.

Pros of Woven Plastic:

• Extremely durable
• Tear Resistant - Great protection against hail and flying debris
• Double Sided allows you to choose the desired diffusion level

Cons of Woven Plastic:

• Higher Cost
• More difficult to put on
• Doesn’t stretch
• Must be used with batten strap
• Heavier

Factors to Consider When Choosing Greenhouse Plastic

Photo by [Lisa Knoebel Photography]

When selecting the best greenhouse plastic, you need to take into account several factors, including your local climate, greenhouse structure, budget constraints, and plant requirements. Here are some critical factors to consider:

Thickness

The thickness of your greenhouse plastic plays a significant role in its durability, light transmission, and insulation properties. A thickness of at least 6 mil is recommended for most greenhouse applications, as it provides a good balance between strength, longevity, and light transmission. Greenhouse plastic comes in many thicknesses, from as thin as 3 mil to as thick as 11 mil.

Size

Measure the length, width, height, and length of the hoops of your greenhouse structure to determine the appropriate size of plastic required. For a detailed guide, check out our article on How to Determine the Size of Greenhouse Plastic You Need. 

Transparency

Greenhouse plastics come in various transparency levels, including clear, opaque, and white. Clear plastic allows the most light, making it suitable for most gardeners. Opaque plastic filters light, which can be useful in warm climates to avoid overheating plants. White plastic provides the least light transmission and has limited applications.

Photo by [Lisa Knoebel Photography]

Single or Double Layer

Many growers wonder if they should use a single or double layer of plastic. While a single layer is great, there are many benefits to using a second layer of plastic. Mainly a double layer will provide extra protection from hail, wind, and also increase the R-factor, basically a way to measure the structure’s ability to resist losing heat.

By using an inflated double layer you can increase the R-factor from .8 to 1.2. If you use end walls you can get your R-factor up into the sixes!

Note that a woven greenhouse plastic can be used as the bottom layer in a double layer setup, but you cannot use a double layer of woven alone. It is simply too heavy to inflate.

Additional Features

Some greenhouse plastics come with additional features, such as anti-drip and anti-dust properties, infrared tinting, double-layer insulation, UV protection, and photo selective properties. These features can help improve the growing environment and extend the lifespan of your greenhouse plastic.

The Best Greenhouse Plastics: Bootstrap Farmers Top Picks

6 Mil Clear Polyethylene Greenhouse Plastic

This greenhouse plastic is a great value. It’s our most affordable option, while still meeting rigorous quality standards. This plastic is 6 millimeters thick and our 5-layer technology makes it extra strong and long-lasting. It even comes with a 4-year warranty.

The UVA coating helps protect it against UV degradation. As with all UV-protected Greenhouse Films, this should not come into direct contact with PVC as it will cause premature degradation.

Features: 

• Anti-dust protection, reduces absorption of dust for long-lasting transmittance
• 4-Year Rating & Warranty
• Light transmittance > 90%
• Light Diffusion 20% 
• 4 Year Warranty makes this plastic NRCS Preferred
• Can be cut to any length

Photo by [Lisa Knoebel Photography]

High Diffusion 6 Mil Open UV Greenhouse Plastic

This UV open, 6 mil plastic is the premiere plastic choice in the floral (excluding roses) and fruit industry. It’s designed to give even more light, better dispersion, and more comfortable temperatures during sunlit hours. 

Its five layers include IR additives, anti-drip condensate, anti-dust, and high light diffusion, which help create more ideal growing conditions and higher yields.

Features:

• Anti-dust (AD) property helps film stay clear of contaminants, improving film light transmission.
• Anti-condensation property
• High diffusion (Diff) for even and homogeneous light distribution on your canopy, eliminating shadow caused by other plants.
• Allows for UV inclusion
• Sheeting has an opaque appearance 
• Infra-red (IR) property aids in keeping your greenhouse temperature higher during cold nights, saving energy costs for heating while keeping things drier.
• 4-Year Rating & Warranty
• Designed to hold heat. Not recommended in areas of high heat without the use of shade cloth.

Greenhouse Woven Plastic 8 mil- Solarig 156- Woven

This plastic offers an upgrade in strength. SOLARIG™ 156 (previously known as SOLARIG™ 140) is the premier woven option for greenhouse and hoop house coverings. 

It is made from coated poly with UV additives for extra protection from degrading and added light diffusion for your plants. This greenhouse plastic is designed to work with spring wire and lock channel applications.

Features: 

• Puncture and Tear Resistant
• 8 mil. thickness
• Anti-fog additive
• 4 Year Warranty when used as a single layer
• 6 Year Manufacturer's Warranty when the interior layer in a 2-layer inflated system (exterior layer should be 4 yr. 6 mil greenhouse plastic)
• Enhanced Light Diffusion
• 88% Light Transmission
• 60% Diffused Light +/- 6% for Matt Finished Side
• 35% Diffused Light +/- 6% for Shiny Finished Side
• Up to 15x stronger than regular Greenhouse Plastic
• Lamination on both sides of the sheet
• 4 layers of thickness to each sheet
• Provides good resistance to strong winds and severe weather

Greenhouse Woven Plastic 11 mil- Solarig 182 - Woven

If you need the strongest, longest-lasting greenhouse plastic you should choose this Solarig 182. 

Features: 

• Puncture and Tear Resistant
• 11 mil. Thickness
• 88% Light Transmission
• 60% Diffused Light +/- 6% for Matt Finished Side
• 35% Diffused Light +/- 6% for Shiny Finished Side
• 96 lb per inch Breaking Strength
• Plastic weighs 5.1 oz per sq. yd.
• Anti-fog additive
• 6 Year Warranty
• Enhanced Light Diffusion
• Up to 15x stronger than regular Greenhouse Plastic
• Lamination on both sides of the sheet
• 4 layers of thickness to each sheet
• Provides optimal resistance to strong winds and severe weather

Light Deprivation Plastic or Silage Tarp

There are some specialty applications in greenhouses where a plastic that is white on one side and black on the other is used in addition to or instead of clear plastic. It can be used for light deprivation to increase the brix of particular crops or to manipulate flowering periods. 

This plastic is also referred to as silage tarp and used for occlusion of weeds. For more on the ways it can be used you can review these articles on Light Deprivation and How to Use Silage Tarps. 

Tools and Tips for Installing Greenhouse Plastic

Proper installation of your greenhouse plastic is essential to ensure its durability and effectiveness. Here are some tools and tips to help you install your greenhouse plastic:

Tools Needed

• Ladders, or a scissor lift for taller greenhouses
• Diagonal cutters or a lineman pliers for cutting spring wire
• Push brooms for guiding the plastic over the structure
• Tennis balls or similar items to protect plastic during installation.*
• Rope
• Box cutter or similar tool for trimming plastic
• Safety gear, such as gloves and goggles
• Greenhouse repair tape, in case of accidents

*Tennis balls, can be placed on pole ends to protect plastic when guiding it over the structure. They can also be tied into a corner of the plastic with rope to be used in pulling it over the length of your structure.

Installation Tips

• Use lock channel and spring wire for secure attachment of your greenhouse plastic.
• Ensure the plastic is pulled tight to prevent rips, stretching, and tears.
• Make repairs as soon as you notice any rips or tears.
• Store your greenhouse plastic in a cool, dry place when not in use.
• Remove snow buildup from your greenhouse plastic to prevent damage.
• Avoid using pesticides in your greenhouse, as they can damage the plastic.

Greenhouse film is straightforward to install. Lock channel and spring wire is the industry standard for properly securing greenhouse plastic. Installing lock channel and spring wire is a simple and economical way of installing greenhouse plastic and other coverings, including poly plastic and shade cloth, to a structure.

The PVC coated spring wire used to secure greenhouse coverings into a lock channel is sometimes referred to as wiggled wire because you will need to "wiggle" it up and down during installation. Spring wire, used in conjunction with the lock channel, forms a tight and secure attachment of your greenhouse covering.

In order to install the spring wire, pull the polyethylene film tight and wiggle the wire back and forth into the channel. Each section of wire is 6.5 feet long so there will be places that you will need to cut the wire to fit. You can use bolt cutters or a metal saw to easily size the sections that you need.

We prefer the method of using spring wire and lock channel over the often used staples and batten board method because it gives the grower the ability to remove and reinstall the plastic without causing damage.  

Click here to learn more about installing greenhouse plastic with lock channel.

BEST WAY TO MAINTAIN GREENHOUSE PLASTIC FOR WARRANTY

Greenhouse film sold through Bootstrap Farmer comes with a 4-year warranty.  In order to ensure that this warranty is valid, manufacturers include set instructions and policies. Store your greenhouse plastic horizontally and away from direct sunlight. Be sure to save a sample size of the greenhouse plastic (2 sq. ft) with the product identification tag. This will help if warranty claims need to be made. Avoid direct contact with non-polyethylene plastics or PVC adhesives as this will void your warranty and cause degradation of the film. 

When getting started on your greenhouse structure, treat any wooden parts with non-oil based fumigant. Use aluminum slats instead of PVC. Before setting the plastic, paint all surfaces that come into contact with the plastic with a white acrylic paint. After setting the plastic on the greenhouse structure, paint thin strips (20 cm) using a white acrylic-based paint directly on the film surface at points of contact between the film and the structure.

Attaching the greenhouse to the structure can be tricky.  It is recommended to start the roll at the top of the gable and unroll it to the length of the structure. Begin this process early morning for cooler temperatures.  Stretch the film to size and return to tighten as temperatures increase in the day. This will ensure a good fit.  Be sure to install the roof and side curtains in the same work window, end-walls can come last.

Ongoing maintenance will include repair of any holes or tears and tightening the plastic between seasons.  It is important to use the correct greenhouse repair tape in order to maintain the warranty.

The use of pesticides and chemical sprays can break down the plastic also voiding the warranty. Avoid contact with the film if ever using a chemical spray. Lastly, shade cloth contact can be damaging to the greenhouse film.  Instead of placing it directly on the film, suspend it between high posts directly over the structure.

Photo by [Lisa Knoebel Photography]

FAQ

Can I reuse greenhouse plastic?

Yes, greenhouse plastic can be reused if it is in good condition and has been properly stored when not in use. 

How do I clean greenhouse plastic?

Rinsing with a garden hose is usually sufficient for cleaning greenhouse plastic. For stubborn spots, use a mild dish soap solution and a soft rag. Avoid using abrasive cleaners or pressure washers, which may damage the plastic.

How long does greenhouse plastic last?

The 4-year rating is the manufacturer’s minimum warranty. Many plastics last years past their warranty. This depends largely on your location, care, and environment. One of our team members just replaced his 6 mil plastic after 11 years of use.

How much greenhouse plastic do I need for my greenhouse?

The size of your greenhouse film can be determined by measuring the length and width of the growing structure that you wish to cover. Account for the total length of the pipes you will use to complete the hoops and the end walls. Roll-up sides will require an extra 4' of plastic.

If you are measuring plastic for the double layer, you will only need enough plastic to cover from hip board to hip board as the second layer will only need to cover the top of the structure. 

Is all plastic sheeting created equally?

No. Regular plastic sheeting from a hardware store has no UV-protection in it. It will quickly turn into plastic confetti within a few months. Ask us how we know.

Does anything cause plastic to deteriorate faster?

PVC will degrade all types of plastic. Do not install greenhouse plastic on PVC unless the PVC has been coated in a protectant. 

The use of pesticides and chemical sprays can break down the plastic and also void the warranty. Overspray from crop treatments can also cause plastic to deteriorate and become brittle. This is true of both organic and conventional treatments. For example sulfur spray to prevent mildew can cause plastic to yellow prematurely. If any spray does get on your greenhouse covering, wash it immediately with mild soap and lots of water. This will help protect your plastic and your warranty.  

Conclusion

Choosing the best greenhouse plastic is a critical decision for any gardener or farmer looking to optimize their growing environment. By considering factors such as material, thickness, size, transparency, and additional features, you can select the perfect greenhouse plastic for your needs. With proper installation and maintenance, your greenhouse plastic will provide an ideal environment for your plants to thrive, ensuring a successful and productive growing season.

Photo Credit Lisa Knoebel Photography