The proper greenhouse fabric, typically called greenhouse plastic, film, poly, and covering, is a vital aspect of building a fully functional greenhouse. Assessing your climate to ensure you have the right greenhouse covering to meet your specific needs allows you to maximize your crop and your overall efficiency. Greenhouse films enable heat retention, which allows you to be in control of the climate. Greenhouse films diffuse light and control harmful UV rays that negatively affect your garden as well as protect your crop from rain, wind, and snow to insure that natural causes do not disrupt your garden.
There are many different types of soft greenhouse fabrics available for your frame depending on your goals. 4 year films are popular due to their balance between benefits, functionality, and cost. 4 year films come in clear, white, infrared/anti-condensate and cooling films for summer or hot geographical locations. For moderate to harsh winters an overwintering film can be used to protect and prolong the life of your greenhouse.
Black-white poly is a reflective option that can be used for either ground cover, bench cover, or photoperiod control; this poly is durable enough to withstand foot traffic or retractable curtain usage. Reinforced poly can also be used for ground coverings, temporary walls, plant dividers, covers and more.
Certain building codes require the use of flame retardant materials, in which case a flame retardant greenhouse film such as GT's White Flame Retardant film can be a great option. Other greenhouse building codes you might run into specifiy that you need to use stiff polycarbonate panels instead of soft poly, read more here.
Please call our expert staff for quotes or questions about what type of poly will work best for your scenario at (541) 480-9392 or fill out our contact form.
Features of Soft Greenhouse Poly
- Heat Retention
- Condensation Control
- 4 year life span
- Folds up to 210% stronger
- High tear strength & puncture resistance
- UV Stabilization
- High light transmission & diffusion
Additional Benefits of Soft Poly
- Lowers greenhouse temperature by 9 degrees relative to outside temp
- Produces high-yielding plants with strong root systems
- Retains moisture in soil
- Inhibits fungus spore development
- Inhibits insect propagation
- Creates comfortable working conditions
Although many factors affect longevity of greenhouse fabrics and plastics, none are more destructive than the sun. Ultraviolet light breaks down plastics quickly. Although all plastics take a beating, UV coatings are specially designed to resist UV and extend the life of the film.
By diffusing the sunlight that reaches the plants, greenhouse film can improve growing conditions by making more photosynthetically active radiation available and in turn improving crop yields.
Some films reduce short wave infrared radiation, reducing temperatures in environments with hot summer months, overall improving conditions and resulting in higher crop yields. In addition, there is less risk of scorching while achieving an optimum rate of photosynthesis, and the plants can develop stronger-than-normal root systems if the conditions, application, and film are optimized.
Superior Light Transmission
Not all grow application poly films are created equally. Films designed for high light transmission significantly increase useful light (light within the PAR range) delivered to the plant to increase yields.
In contrast to soft greenhouse fabrics, greenhouse polycarbonate panels are a stiff greenhouse poly. There are benefits to a stiff polycarbonate panel including a better insulative value and a higher weather resistance. Polycarbonate paneling can last up to twice as long as soft poly and often has built-in condensate control. Some building codes often require a rigid greenhouse instead of a cold frame built with soft poly. As most things in life, all these benefits come at a cost. Greenhouse poly panels are more expensive than soft greenhouse fabrics.
If you are using a tarping system, a popular method is to use panda film that is pulled over the greenhouse at certain times of day. This can be an inexpensive option, however, it is a strenuous daily activity especially on larger cold frames.
Can I use regular plastics like Visqueen or other polyethylene films from Home Depot or Lowes to cut costs?
A: A generic polyethylene film is designed to accommodate simple applications and does not have properties supportive of plant growth. Generic films are especially lacking UV coatings which protect against yellowing and cracking in the sun. Our line of plastics have high durability, toughness, higher light transmission, and higher puncture and tear strength, among other useful properties. Although generic plastics have lower initial costs, at bare minimum regular replacement costs and reduced light transmission drive up overall costs in the long run. Starting out with the right coverings drives overall costs down and improves crop returns which far outweigh initial savings with generic film.
How many different grades of plastics are there? What are the benefits of higher grades?
There are different poly types and grades for each grow operation and climate. Choosing the right covering will provide the best environment for plants and result in the higher yields and keep costs down. Reach out to us to get a film recommendation for your application.
How does light diffusion help the plant?
Much of the useful light plants get from the sun hits the leaves directly, but some light bounces off of various surfaces and reaches the leaves indirectly. Depending on climate, sun intensity, and plant type, there’s an ideal amount of direct sunlight the crop should get. Beyond this direct light threshold, diffuse light can further increase useful light for the plant. Polys can be used to both limit direct sunlight to protect the plant, and turn that excess direct sunlight into diffuse light to achieve an optimum rate of photosynthesis and further increase yield and quality. A plant can benefit from the scattering of sunlight rays and grow up to 30% faster when all leaves are bathed in light, not just the upper canopy.
How can you tell if a poly has aged poorly?
Greenhouse poly degrades as the material ages. Many growers replace covering after they show visible signs of wear to save on cost. There are hidden costs associated with poorly performing plastics, however, which should be avoided when possible prior to visible degradation. Yellowing, darkening, scratching, cracking, punctures, and tearing can all impact performance and reduce crop quality and growth rate in different ways. For example any degradation which creates a roughened surface texture can provide a foothold for mold. A yellowed surface can simply block useful spectrum and slow down the growth rate of the plant. Cracking, tearing,and punctures can affect overall temperatures in the greenhouse as well as introduce unwanted temperature variations to plants closest to the leaks. Darkening usually happens more in certain zones than others creating inconsistency between plants. There are already so many factors that can negatively affect plants, eliminating the easy ones is highly desirable.