Top Ten Tips for Greenhouse Plastics
Greenhouse plastics are essential covering materials that directly impact your crop’s success. You might also hear them called greenhouse poly (or double poly), glazing, covering, or film. Some greenhouses use other materials such as polycarbonate paneling or glass, but flexible lightweight plastics are the most common.
1. Get the Best Greenhouse Plastic Lifespan
Choosing a greenhouse plastic involves factoring in many considerations. One major consideration is the lifespan of the plastic. Most greenhouse plastics have either a 1-year or 4-year lifespan. Nursery plastics are usually rated for 1-year of use and need to be recycled at the end of the season. However, the cost of buying plastics annually is considerably more than buying a 4-year lifespan plastic like TuffliteIV or TuffliteIR.
2. Make Sure Your Plastic Suits Your Greenhouse Frame
Semi-gable greenhouse frames are the best option for year-round greenhouse operations in areas that get snow. The steep peak allows the greenhouse to shed snow naturally. If you are leaving your greenhouse plastic on all year round, you still may need to invest in a double poly inflation system and/or greenhouse heater to ensure the plastic can withstand snowfall. Quonset greenhouses enable easier greenhouse plastic removal and installation but they do not support snowfall well. They are more suitable for seasonal use than year-round operation.
3. Make Sure Your Greenhouse Plastic Suits Your Climate
Different types of greenhouse plastic have different constructions. They may have more or less layers of plastic and also can contain additives such as anti-condensate, anti-dust, UV stabilizers, and infrared radiation filtration. There are also woven plastics with extra strength and black and white light deprivation plastics. When venturing into greenhouse production, it is important to really understand your site’s climate. Consider factors like:
- How many DLI does my site get throughout the growing season?
- How intense is the solar radiation at my site?
- What range of outdoor temperatures does the site experience?
- Will the site get snow, fog, heavy rain, heavy wind, frequent cloud cover, or extreme weather events?
TuffliteIR is one of the best greenhouse plastics you can choose because it has additives to prevent condensation, resist dust, filter UV rays and infrared rays, and provides the highest level of thermal stability. This plastic works to keep your greenhouse energy efficient while stabilizing environmental conditions.
You may also consider using a double poly inflation kit where two sheets of plastic are inflated with air via a motor. This system provides insulation for energy efficiency, environmental stability, and withstands snow.
4. Use the Right Greenhouse Plastic in the Right Places
You don’t have to choose just one type of greenhouse plastic for your entire structure. In fact, it is really beneficial to consider using different types for different purposes. Here are some examples:
- End walls are not a major source of light, you may opt to use woven greenhouse plastic or polycarbonate panels that are more durable and offer insulation and thermal stabilization.
- Greenhouse frames are the major area where light (and heat) enter the structure, you’ll want a plastic that has suitable light transmission with protection from harmful solar radiation that can damage plants.
- Light deprivation greenhouses will need to use both clear plastic and black and white plastic. External light dep systems will roll over the clear plastic so you may benefit from choosing a stronger plastic with less light transmission but greater ability to withstand use.
- Roll-up sides are rolled up for ventilation during the day and closed at night. This high-use system may also benefit from sacrificing light transmission for durability.
5. Understand Light Transmission and Diffusion
Some light diffusion is beneficial because it can reach more plants and more parts of the plant. Direct sunlight only reaches the upper canopy of the plants and slows the growth rate below the canopy. Direct light also creates more heat in the greenhouse versus diffused light which distributes heat more evenly. That is to say that losing some light transmission and gaining some light diffusion is actually good in many situations!
- Direct Solar Radiation: Sunlight hits the greenhouse plastic and is filtered through the plastic as it enters directly into the structure
- Diffused Light Type 1: Sunlight hits the greenhouse plastic and is scattered as it is filtered through the plastic as it enters the structure
- Diffused Light Type 2: Sunlight hits clouds and is scattered in the atmosphere, then scattered again as it is filtered through the greenhouse plastic
If you are located at a site that frequently has cloud coverage, fog, smoke, or haze, you may want to stick with a plastic that has the most light transmission. However, your goal is to reduce heat gain during the day, reduce heat loss during the night, and provide sufficient light for plants. With this in mind, you need to take a balanced approach when selecting greenhouse plastic.
TuffliteIV will have a light transmittance of about 85% to 87% for a single layer of film and about 74% to 77% for a double layer. With TiffliteIR you will have slightly less light transmittance but greater thermal stability to support sensitive plants and combat heat and harmful radiation in hotter climates like Arizona or high desert areas in Oregon and Colorado.
6. Recycle Your Used Greenhouse Plastic
It is fairly easy to recycle your used greenhouse plastic. Most localities can provide specific guidance through their agricultural departments or recycling programs. Recycling companies like Power Plastic Recycling offer recycling services in many states such as California, Oregon, and Oklahoma. No matter where you live, you can find out where to recycle your greenhouse plastic through ACRC. You’d be surprised how many recycling businesses are working to recycle agricultural waste like used greenhouse plastics. You might also find some other purpose for your used plastics, but beware that the chemicals start to break down after the lifespan is reached. The best option is to recycle them to keep chemical contamination out of the environment.
7. Repair Tears in Greenhouse Plastic
Keeping your greenhouse sealed is important for keeping pests out. It is also important for maintaining environmental conditions efficiently. Greenhouse repair tape can be used to repair small rips and tears in your greenhouse plastic.
8. Clean Your Greenhouse Plastic
Chemicals need to be kept away from plastic and can lead to damage. Keeping the plastic clean by washing it is also important. Dust and dirt will reduce light transmission, and moss and algae growth can harbor pests and spread pathogens. You can clean your greenhouse using a gentle detergent and a soft cloth or sponge, followed by a rinse to remove soap. Be gentle when cleaning plastics and avoid harsh scrubbing. A pressure washer is too rough to use, but a hose with a sprayer can assist in hard to reach places.
9. Install Greenhouse Plastic Correctly
The best way to install greenhouse plastic is by using aluminum channel base and wiggle wire. The plastic is pulled over the channel base, then secured with wiggle wire that is inserted into the channel over the plastic. These systems will hold your plastic in place and seal the structure effectively.
10. Get Expert Support
If you are leaving this article with more questions than answers, that’s ok. Greenhouses are simple structures that have surprisingly complex engineering. The staff at Hortitech Direct have actual growing experience and can help you decide on what greenhouse plastic best meets your goals and site conditions. Whether you are looking to save money, conserve energy, operate more sustainably, or all three, we understand your diverse needs and can offer solutions to meet them.