Choosing the right plastic for a greenhouse is one of the most important decisions when building or upgrading a greenhouse. The covering material directly affects light transmission, heat retention, durability, and crop growth. Many greenhouse growers prefer plastic coverings because they are affordable, lightweight, and easy to install compared to glass panels.

However, not all plastics are suitable for greenhouse use. The thickness, UV resistance, insulation properties, and lifespan of greenhouse plastic all determine how well it performs in different climates.

This guide explains what plastic to use for a greenhouse, including the best thickness (mil), installation methods, UV-treated plastics, and comparisons between PVC and polycarbonate greenhouse coverings.

What Plastic Should You Use for a Greenhouse?

Most greenhouse growers use polyethylene plastic film for greenhouse coverings. This type of plastic is specifically designed for agricultural applications and allows sunlight to enter while trapping heat inside.

Common Types of Greenhouse Plastic

The most widely used greenhouse plastics include:

• Polyethylene plastic film
• Polycarbonate panels
• PVC greenhouse film
• Reinforced polyethylene
• Diffused greenhouse plastic

Among these options, polyethylene greenhouse plastic is the most popular because it provides a balance of affordability and performance.

Greenhouse Plastic Thickness: What Mil Plastic for Greenhouse?

The thickness of greenhouse plastic is measured in mil, which represents one-thousandth of an inch (0.001 inch).

Thicker plastic generally lasts longer and provides better insulation.

Common Greenhouse Plastic Thickness Chart

Recommended Thickness

For most greenhouse applications, 6 mil UV-treated polyethylene plastic is considered the best option because it provides:

• Good durability
• Excellent light transmission
• Long lifespan

Types of Greenhouse Coverings

Different greenhouse coverings provide different benefits depending on the climate and budget.

Polyethylene Greenhouse Film

Polyethylene film is the most commonly used greenhouse covering.

Advantages

• Affordable
• Lightweight
• Easy to install
• Good light transmission

Disadvantages

• Needs replacement every few years
• Can tear under strong winds if not secured properly

Polyethylene film is widely used for hoop houses and backyard greenhouses.

Polycarbonate Panels

Polycarbonate panels are rigid plastic sheets that offer excellent insulation.

Benefits

• Very durable
• UV resistant
• Better heat retention
• Long lifespan (10–15 years)

Disadvantages

• More expensive than polyethylene
• Requires more complex installation

Polycarbonate panels are commonly used in permanent greenhouses.

Reinforced Polyethylene Plastic

Reinforced polyethylene contains a mesh grid embedded within the plastic film.

Advantages

• Stronger than standard plastic film
• Tear resistant
• Good for windy climates

Disadvantages

• Slightly reduced light transmission
• Higher cost than basic plastic film

Diffused Greenhouse Plastic

Diffused plastic spreads sunlight evenly across the greenhouse.

Benefits

• Reduces plant scorching
• Improves light distribution
• Encourages uniform plant growth

Many professional growers prefer diffused plastic because it improves crop yield and plant health.

UV Treated Plastic for Greenhouse

Standard plastic quickly degrades when exposed to sunlight. This is why greenhouse plastic must be UV treated.

UV-treated plastic contains special additives that protect the material from ultraviolet radiation.

Benefits of UV-Treated Greenhouse Plastic

• Longer lifespan
• Reduced cracking and brittleness
• Maintains transparency longer
• Protects crops from harmful UV rays

Most high-quality greenhouse plastics are designed to last 3–5 years with UV protection.

Is PVC or Polycarbonate Better for Greenhouses?

Both PVC and polycarbonate materials are used in greenhouse construction, but they serve different roles.

PVC Greenhouses

PVC is often used for greenhouse frames rather than coverings.

Advantages of PVC

• Affordable
• Lightweight
• Easy to assemble
• Ideal for DIY greenhouses

Disadvantages

• Less durable than metal frames
• Can warp under heat exposure

PVC greenhouses are often used for small backyard or temporary greenhouses.

Polycarbonate Greenhouses

Polycarbonate is widely used for greenhouse panels and coverings.

Advantages

• Excellent insulation
• Very strong material
• UV resistant
• Long lifespan

Disadvantages

• Higher upfront cost
• Requires proper installation

PVC vs Polycarbonate Comparison

For long-term greenhouses, polycarbonate panels are generally better than PVC coverings.

How to Attach Plastic to a Greenhouse

Attaching plastic correctly to a greenhouse is essential for preventing wind damage, improving insulation, and extending the lifespan of the greenhouse covering. Most greenhouse coverings use UV-treated polyethylene plastic (usually 6 mil thickness) because it is durable and allows good light transmission.

Below are the proper steps to securely attach plastic to a greenhouse frame.

Step 1: Choose the Right Greenhouse Plastic

Before installation, select plastic specifically designed for greenhouse use.

Recommended features:

• 6 mil UV-treated polyethylene plastic
• Anti-drip or anti-condensation coating
• High light transmission (80–90%)

Avoid using regular construction plastic because it degrades quickly under sunlight.

Step 2: Prepare the Greenhouse Frame

Inspect the greenhouse frame carefully before installing plastic.

Important preparations include:

• Remove sharp edges or rough surfaces
• Tighten bolts and structural connections
• Clean the frame to remove dirt or debris

This prevents tearing and helps the plastic sit evenly on the structure.

Step 3: Measure and Cut the Plastic

Measure the greenhouse dimensions accurately before cutting the plastic sheet.

Guidelines:

• Leave extra plastic (12–18 inches) on each side
• Use one continuous sheet if possible
• Avoid seams whenever possible

Extra material allows the plastic to be stretched tightly and secured properly.

Step 4: Install Plastic on a Warm, Calm Day

Greenhouse plastic becomes easier to stretch when it is warm.

Ideal installation conditions:

• Warm weather (above 60°F / 15°C)
• Minimal wind
• Dry conditions

Warm plastic stretches slightly, which helps achieve a tighter fit.

Step 5: Position the Plastic Over the Frame

Place the plastic over the greenhouse structure.

Tips for positioning:

• Center the plastic evenly on the frame
• Ensure equal excess material on all sides
• Avoid dragging the plastic across sharp edges

For larger greenhouses, having two or three people makes this step easier.

Step 6: Secure Plastic Using Wiggle Wire and Channel

The most common professional method uses wiggle wire and channel systems.

How it works:

1. Attach metal channels along the greenhouse frame.
2. Press the plastic into the channel.
3. Insert wiggle wire to hold the plastic tightly in place.

Benefits of wiggle wire systems:

• Very secure installation
• Easy plastic replacement
• Prevents tearing

This method is widely used in commercial greenhouses.

Step 7: Use Greenhouse Clips or Batten Tape

For smaller greenhouses, plastic can also be secured using clips or tape.

Common fastening methods:

• Greenhouse spring clips for metal frames
• Batten tape wrapped around the frame
• Wooden lath strips screwed over the plastic

These methods hold the plastic firmly without puncturing it excessively.

Step 8: Stretch the Plastic Tight

Stretch the plastic tightly across the frame to prevent sagging.

Why this matters:

• Prevents water pooling
• Reduces wind damage
• Improves greenhouse insulation

However, avoid overstretching, which may cause tearing.

Step 9: Seal the Edges and Bottom

Secure the plastic edges tightly to prevent wind from entering.

Common sealing methods:

• Bury the plastic edges in soil
• Attach plastic to base boards
• Use weighted pipes or boards

Proper sealing helps maintain stable greenhouse temperatures.

Step 10: Add Doors and Vent Openings

Cut openings for greenhouse doors and ventilation after the plastic is secured.

Tips:

• Reinforce edges with tape before cutting
• Leave enough plastic to fold around door frames
• Secure edges tightly to prevent tearing

Ventilation openings help regulate temperature and humidity inside the greenhouse.

Greenhouse Plastic Attachment Methods Comparison

Wiggle wire systems provide the most secure and professional installation.

Tips to Make Greenhouse Plastic Last Longer

Proper installation can extend greenhouse plastic lifespan.

Helpful tips include:

• Install plastic during warm weather
• Avoid sharp edges on frames
• Use UV-treated plastic
• Keep plastic tight to prevent wind damage
• Inspect regularly for small tears

High-quality greenhouse plastic can last 3–5 years when properly installed.

Common Mistakes When Attaching Greenhouse Plastic

Many greenhouse owners make mistakes that reduce plastic lifespan.

Common problems include:

• Installing plastic during windy weather
• Using construction plastic instead of greenhouse film
• Leaving plastic loose or sagging
• Attaching plastic with too many punctures
• Ignoring small tears that grow larger

Avoiding these mistakes ensures better greenhouse performance.

Single Layer vs Double Layer Greenhouse Plastic

Greenhouses can use either single-layer or double-layer plastic coverings.

Single-Layer Plastic

Advantages:

• Lower cost
• Easier installation
• Good light transmission

Disadvantages:

• Less insulation
• Higher heating costs

Double-Layer Plastic

Double-layer greenhouses use two plastic sheets with air blown between them.

Advantages:

• Better insulation
• Reduced heat loss
• Improved energy efficiency

Disadvantages:

• Higher installation cost
• Requires inflation system

Comparison Chart

Commercial growers often use double-layer polyethylene plastic to reduce heating costs.

Best Plastic for Different Greenhouse Types

Different greenhouse structures require different coverings.

Choosing the right plastic depends on budget, climate, and greenhouse size.

How Long Does Greenhouse Plastic Last?

The lifespan of greenhouse plastic depends on several factors.

Average Lifespan

Regular maintenance and proper installation can extend the lifespan of greenhouse coverings.

Tips for Choosing the Best Greenhouse Plastic

Consider Climate

Cold climates require thicker plastic or double-layer insulation.

Check Light Transmission

Plants require at least 80–90% light transmission for healthy growth.

Look for UV Protection

UV-treated plastic lasts significantly longer.

Use Anti-Condensation Films

Some greenhouse plastics include anti-drip coatings that prevent water droplets from falling on plants.

Frequently Asked Questions

What thickness plastic is best for a greenhouse?

Most growers use 6 mil UV-treated polyethylene plastic, which offers durability and good light transmission.

How long does greenhouse plastic last?

High-quality greenhouse plastic typically lasts 3–5 years.

Can you use regular plastic sheeting for a greenhouse?

Regular plastic is not recommended because it degrades quickly under sunlight.

What is the best greenhouse covering material?

Polyethylene film is the most common, while polycarbonate panels provide the longest lifespan.

Should greenhouse plastic be clear or opaque?

Clear plastic allows maximum light transmission, while diffused plastic distributes light evenly.

Is polycarbonate better than polyethylene?

Polycarbonate is more durable but also more expensive.

Can greenhouse plastic survive strong winds?

Yes, if properly secured using wiggle wire or greenhouse clips.

Does thicker plastic improve insulation?

Yes, thicker plastic and double-layer systems improve insulation.

How often should greenhouse plastic be replaced?

Most polyethylene greenhouse plastics should be replaced every 3–5 years.

Is UV-treated plastic necessary for greenhouses?

Yes. UV-treated plastic prevents rapid deterioration from sunlight exposure.

Conclusion

Selecting the right plastic for your greenhouse is essential for creating a successful growing environment. The best greenhouse coverings provide high light transmission, durability, UV resistance, and good insulation.

For most growers, 6 mil UV-treated polyethylene plastic offers the best balance of affordability and performance. Commercial greenhouses may benefit from double-layer polyethylene or polycarbonate panels for improved insulation and long-term durability.

By choosing the correct greenhouse plastic and installing it properly, growers can create a productive, energy-efficient greenhouse that supports healthy plant growth throughout the year.

References

1. https://www.greenhousemag.com/article/choosing-greenhouse-coverings/
2. https://extension.psu.edu/greenhouse-coverings-for-protected-culture
3. https://www.canr.msu.edu/resources/greenhouse-plastics
4. https://www.uvm.edu/extension/agriculture/greenhouse-coverings
5. https://www.rhs.org.uk/advice/profile?pid=751

David Holtzman

I’m David man behind Lawn Mowerly; I’ve been dealing with lawnmowers and Tractors with my father since I was a kid. I know every make and model and what each one is capable of and love helping people find the perfect equipment for their needs.