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.
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.
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.
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:
So how do you determine the right thickness for your needs? Here are the key factors to consider:
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 |
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.
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.
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.
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.
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:
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 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:
Downsides of polycarbonate panels:
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.
Here are some expert tips to help your greenhouse plastic last longer:
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.
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.
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.
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.
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.
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.
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