How thick does greenhouse plastic need to be?

Greenhouse plastic—also known as polyethylene film—is a critical component of any agricultural greenhouse. But one of the most common questions growers ask is: “How thick does greenhouse plastic need to be?” The answer depends on a few factors including climate, crop type, expected lifespan, and budget.

In this article, we’ll explain:

• The standard greenhouse plastic thickness options

• How thickness affects durability and insulation

• Which thickness suits which climate and use case

• Tips for selecting the right plastic for your structure

Common Greenhouse Plastic Thicknesses Explained

Greenhouse plastic is typically measured in mils, where 1 mil = 0.001 inch (0.0254 mm). The most commonly used greenhouse films are:

• 4 mil (0.10 mm)

• 6 mil (0.15 mm)

• 8 mil (0.20 mm)

Let’s compare these in more detail.

4 Mil Greenhouse Plastic

Best For:

• Temporary structures

• Seasonal growers

• DIY garden tunnels

Pros:

• Lightweight and affordable

• Easy to handle and install

Cons:

• Lower durability

• Typically lasts 1–2 seasons

• More prone to tears and UV degradation

Use this option if you only grow part of the year or are covering a small space temporarily.

6 Mil Greenhouse Plastic

Best For:

• Commercial growers

• Year-round protection

• Standard high tunnels

Pros:

• Industry standard for durability and insulation

• UV-resistant versions last up to 4 years

• Good balance between cost and lifespan

Cons:

• Heavier than 4 mil, needs stronger frame

• Slightly higher cost

This is the most popular choice for commercial greenhouses and agricultural farms. 6 mil plastic is also required for USDA NRCS compliance in many greenhouse funding programs.

8 Mil Greenhouse Plastic

Best For:

• Harsh weather regions

• Heavy snow/wind load zones

• Long-term installations

Pros:

• Extremely durable and tear-resistant

• Excellent insulation and UV protection

• Can last 5+ years with proper care

Cons:

• More expensive

• Requires sturdy structural support

• Less flexible, harder to install

If you’re investing in a long-term greenhouse in an extreme climate (snow or high wind), 8 mil may save you replacement costs in the long run.

How Plastic Thickness Affects Greenhouse Performance

Here’s what thickness impacts in a practical sense:

Climate Considerations

Different regions require different thickness levels based on local weather:

• Hot climates (e.g., Africa, Middle East):
  6 mil UV-resistant film works best; look for anti-drip coating to reduce internal humidity.

• Cold climates (e.g., Canada, Europe):
  Use 6 mil or 8 mil double-layered film with air inflation for better insulation.

• Tropical climates:
  6 mil film with light diffusion technology improves plant growth and reduces sunburn.

Choosing the Right Greenhouse Plastic Thickness: Questions to Ask

Ask yourself:

• Will the greenhouse be used year-round or seasonally?

• Is your region prone to strong winds or heavy snow?

• What is your budget for upfront vs. long-term maintenance?

• Do you need to meet any government or agricultural compliance standards?

Additional Features to Consider

Besides thickness, here are some added-value features to look for in greenhouse plastic:

• UV Stabilizers: Prevent film from breaking down in sunlight

• Anti-Drip Coating: Reduces condensation and mold

• Light Diffusion: Scatters light for more even plant growth

• Infrared Additives: Improves heat retention for cold nights

Buying Tips: Wholesale or Retail?

• Retail buyers: May purchase 4 or 6 mil film in rolls of 3–6 meters width.

• Wholesale buyers / greenhouse builders: Often order customized roll widths and lengths, usually 100–200 microns (4–8 mil), in bulk.

If you are a greenhouse installer or agri-business purchasing in volume, contact a manufacturer directly for custom sizes and factory pricing.

Conclusion: So, How Thick Should Greenhouse Plastic Be?

For most commercial and semi-commercial greenhouses, 6 mil plastic film is the best overall choice. It offers the right balance of durability, insulation, and cost-efficiency, and is suitable for most climates.

If you're in an area with harsh winters or are building a long-term structure, 8 mil plastic is worth the investment. For temporary or hobby use, 4 mil will do the job.