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How Thick is Greenhouse Plastic? A Grower's Guide to Choosing the Right Thickness

How Thick is Greenhouse Plastic? A Grower's Guide to Choosing the Right Thickness

A greenhouse provides an ideal controlled environment for growing plants, protecting them from harsh weather while maintaining optimal temperature and humidity levels. A critical component of any greenhouse structure is the plastic covering or sheeting that acts as the barrier between the inside and outside environments. Greenhouse plastic comes in varying thicknesses, so making the right choice is essential to get the best performance for your needs.

In this comprehensive guide, we’ll explore the typical thickness range for greenhouse plastic, the factors that determine the ideal thickness, the pros and cons of different options, and key considerations for selecting the right greenhouse plastic film for your climate and crops.

Key Takeaways

  • The typical thickness range for greenhouse plastic is 4 to 8 mils. Thinner 3-4 mil plastic works for short-term structures. Thicker 8-12 mil plastic provides maximum durability.

  • For full-season greenhouses in moderate climates, 6 mil plastic is often the recommended thickness for good performance.

  • In cold climates and commercial operations, 8-12 mil plastic provides the greatest insulation and durability over many seasons.

  • With proper installation and care, quality greenhouse plastic can last multiple years. Proper support and UV protection are key to maximizing lifespan.

the interior of a hoop tunnel greenhouse with plastic sheeting

    Introduction to Greenhouse Plastic

    Greenhouse-grade plastic film, also called polyethylene plastic, is specially designed to transmit light while insulating the greenhouse. This clear plastic sheeting is commonly made of polyethylene resin that can withstand exposure to UV radiation from the sun and resists tearing.

    Greenhouse plastic is a critical component that significantly impacts the performance and life of your greenhouse. It protects plants from harsh weather conditions like rain, hail, high winds, and extreme temperatures. The plastic forms a barrier that keeps interior warmth in and cold drafts out while allowing sunlight to pass through. It also prevents the entry of insects and pests that could damage crops.

    Choosing the right thickness of greenhouse plastic is important to get the best longevity, insulation, light transmission, and durability. Leading manufacturers recommend polyethylene plastic ranging from 4 to 8 mils (1 mil = 0.001 inch) for most greenhouse applications. The ideal thickness depends on several factors which we’ll examine next.

    How Thick Should Greenhouse Plastic Be?

    The typical thickness range for greenhouse plastic sheeting is 3 to 12 mils, though 4 to 8 mils is recommended for most uses. Thinner plastic like 3 to 4 mils may be suitable for short-term season extension on tunnels or cold frames. Thicker plastic in the 8 to 12 mil range provides greater insulation and durability for commercial operations.

    Here is an overview of the typical thickness recommendations:

    • 3-4 mil plastic: Short-term use such as low tunnels or season extension
    • 6 mil plastic: Recommended for full-season protection in most climates
    • 8-12 mil plastic: Extra durability for commercial greenhouses and cold climates
    • 16 mil & above: Extremely thick for permanent installations

    Key Considerations When Choosing Greenhouse Plastic Thickness

    So how do you determine the right thickness for your needs? Here are the key factors to consider:

    Climate and Insulation Needs

    The thickness of the plastic will impact insulation capability. Thicker plastic provides better insulation value, reducing heat loss in colder climates. Greenhouse plastic thickness should be selected based on your lowest expected temperatures.

    For climates with moderate winters, a 4 to 6-mil thickness is often sufficient. Colder regions may benefit from 6 to 8 mil plastic. In extreme northern climates, 8 to 12 mils provide maximum insulation during frigid winters.

    Climate Recommended Thickness
    Moderate 4-6 mil
    Cool Summer 6-8 mil
    Cold Winter 8-12 mil
    Very Cold Winter 10-16 mil

    Duration of Use

    Another consideration is how long you intend to use the plastic covering. Thinner greenhouse plastic like 4 mils will typically last one growing season before needing replacement.

    Thicker 6 to 8 mil plastic will last 2 to 4 years, while 10 to 12 mil films may get 4 to 6 years of use if properly cared for. Weigh plastic lifespan against replacement costs to choose the best value.

    Light Transmission Needs

    Thicker plastic can slightly reduce light transmission, though the effect is minimal. Most polyethylene greenhouse films transmit over 90% of light.

    Going from 4 to 8 miles only reduces transmission by 1-2%. Only consider this if growing high-light crops like tomatoes or peppers. Thinner plastic is better for maximizing light.

    High Wind and Snow Load Potential

    In areas with heavy snowfall or high winds, a thicker greenhouse plastic of 6 to 8 mils helps withstand snow load and resists ripping or puncturing. Reinforced poly with an internal scrim provides even greater tear resistance.

    Types of Crops

    Certain crops like orchids and onions favor more diffused light. Thicker poly films can help diffuse direct sunlight. But most plants grow fine under clear 4 to 6 mil plastic.

    Consider crop needs, but the light diffusion benefits of thicker plastic are minimal for most uses.


    Thicker greenhouse plastic costs more initially. 4 to 6 mil plastic for smaller structures can be purchased for around $100 to $600. Commercial-sized 8 to 12 mil plastic for large greenhouses can cost $1,500 to $5,000 to install.

    Weigh the lifespan vs. cost to get the best return. Thinner plastic may need replacing yearly while thicker films provide multi-year performance.

    Common Greenhouse Plastic Thicknesses and Uses

    Now that we’ve covered the factors that determine the ideal thickness, let’s look at some of the most common options and how they’re used:

    4 mil

    • The thinnest plastic commonly used for greenhouse covering
    • Less expensive, making it a good choice for budget-conscious growers
    • Provides about 85% light transmission
    • Suitable for short-term season-extending applications like cold frames and low tunnels
    • Typically lasts 1 growing season before requiring replacement
    • Used by hobby greenhouses, market farmers, and growers doing off-season extension

    6 mil

    • Recommended thickness for general greenhouse use by many manufacturers
    • Provides excellent light transmission of 90%
    • Adds insulation for cooler weather while minimizing light loss
    • Withstands moderate snow load and wind
    • Lasts 2 to 4 seasons before replacement needed
    • Used by commercial greenhouses, market farmers, and intermediate hobby growers

    8 mil

    • Provides increased durability over 6 mil plastic
    • Offers good insulation for cold climates, reducing heat loss
    • High light transmission of 91%, comparable to thinner films
    • Withstands very heavy snow load and high wind conditions
    • Will last 3 to 6 years with proper maintenance
    • Trusted by professional growers and commercial operations

    10 to 12 mil

    • Thickest plastic films used for covering large commercial greenhouses
    • Provides maximum insulation value, ideal for cold northern climates
    • Highly resistant to punctures and tears
    • Withstands heavy snow loads and high winds
    • May diffuse light more than thinner options
    • Lifespan of 5 to 8 years with proper care
    • Used for extra durability in commercial operations

    In general, the thicker the plastic, the more durable, long-lasting, and insulating it will be. The tradeoff is that thicker plastic can be less transparent and more expensive.

    Polycarbonate Panels - An Alternative Option

    Polycarbonate panels are a rigid, multi-wall plastic alternative to polyethylene film coverings. Polycarbonate is available in thickness from 10 to 25 millimeters typically.

    Benefits of polycarbonate panels:

    • Extreme impact and tear resistance
    • Maintains transparency for light transmission
    • Excellent insulation value - even better than polyethylene
    • Long lifespan of up to 10 years

    Downsides of polycarbonate panels:

    • Much higher cost than polyethylene film
    • Requires more complex installation
    • Might need ventilation to prevent overheating
    • Can have issues with condensation buildup

    Polycarbonate is best suited for permanent commercial greenhouses that justify the higher investment. For hobbyists and high tunnels, polyethylene is usually the more cost-effective choice.

    Pro Tips for Maximizing Greenhouse Plastic Durability

    Here are some expert tips to help your greenhouse plastic last longer:

    • Support the plastic properly to prevent sagging, which stresses the plastic.
    • Use opaque reinforced plastic for end walls and doors to prevent UV damage. Clear plastic should only be used on the roof and sides.
    • Remove plastic coverings during extreme high winds to prevent wind damage.
    • Inspect regularly for rips, tears, or gaps, and repair immediately with greenhouse repair tape.
    • Wash off accumulated dirt, leaves, and debris regularly using a low-pressure hose, soft brush, and mild soap.
    • Avoid contact with chemicals like fertilizers or pesticides that could degrade the plastic.
    • Re-tighten bolts, straps, and wiggle wire that hold the plastic in place to prevent sagging over time.


    Selecting the proper thickness of greenhouse plastic is crucial for creating an optimal growing environment. Consider climate, budget, and desired lifespan when choosing thickness. While thin plastics work for short-term use, most operations need at least 6 mils for full-season protection. For commercial growers and cold climates, 8-12 mil plastic provides maximum resilience and insulation. With proper installation and care, quality greenhouse plastic can last many seasons. Investing in the right thickness provides environmental control to boost plant growth while avoiding excess material costs.


    Should I choose regular plastic or twin wall polycarbonate for my greenhouse?

    For most growers, regular single layer polyethylene plastic is the best choice for greenhouses due to lower cost and easier installation compared to rigid multi-wall polycarbonate panels. Polycarbonate excels in toughness but is more expensive. Polyethylene film in the 4-8 mil thickness range allows great light transmission for plant growth.

    How many square feet of plastic sheeting do commercial greenhouse contractors recommend?

    Commercial greenhouse contractors and distributors across the construction industry typically recommend at least 6 mil, UV-treated polyethylene plastic. The recommended amount is around 4 square feet of plastic film per square foot of greenhouse, which allows for sufficient overlap and surface tension for maximum infrared light transmission and insulation.

    How does greenhouse plastic thickness affect light transmission and longevity?

    Thicker plastic films have slightly lower light transmission, but the effect is minimal. Going from 4 mil to 8 mil plastic only reduces light by 1-2%. The main benefit of thicker plastic is much greater tenacity and insulation capability. 8-12 mil films will withstand weather and last 4-6 years, versus 1-2 years for thinner 4-6 mil plastic.

    How long does greenhouse plastic last before needing replacement?

    A: Greenhouse plastic lifespan depends on thickness and proper installation. Thinner 4 mil plastic is common for one year use on narrow tunnels. 6 mil may last 2-4 years, while 8-12 mil plastic films can endure for 4-6 years with care. Frequent inspection, cleaning, and repair help maximize lifespan.

    What width of plastic sheeting do most growers trust for building a greenhouse? 

    Most greenhouse growers trust 4-8 mil polyethylene plastic sheeting that's around 40-60 inches wide as ideal for building a greenhouse structure. Wider sheets with reinforcement of weave along the edges provide sturdiness across the entire width of the plastic. The weave prevents tearing and degradation along the edges.

    Previous article How to Properly Anchor a Greenhouse for Safety and Stability
    Next article How Does a Greenhouse Work: The Science Behind the Greenhouse Effect

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    About The Author

    Andy Wu - Resident Expert

    Andy Wu - Resident Expert

    Andy Wu is the resident backyard products expert and hails from Atlanta, Georgia. His passion for crafting outdoor retreats began in 2003.

    As a fellow homeowner, he founded Backyard Oasis to provide top-quality furnishings and equipment, collaborating with leading manufacturers.

    His main focus is on sheds and generators!

    In his spare time he like to hike the tallest mountains in the world and travel with his family.

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