Poly-Hort B.V.

Greenhouse Covering Films


Greenhouse covering film has high mechanical properties to withstand maximum stress during installation. The main purpose of greenhouses is to create an internal environment favorable to plant growth regardless of the external environment and to extend the growing season as well as the quality and crop yield. Better control equals better crop yield and quality. This all comes about because of the ability to control
the microclimate in terms of light, temperature, humidity and the physical protection of the crop (from winds, rain, snow etc).

Thickness range: 80-203 microns (3.14 - 8 mil). {According to customer’s order}
Width range: 1 to 15 meters (39”-49’) {According to customer’s order}
UVA Durability: 6 – 48 months {According to customer’s order}


Cover film properties:

basic properties:

  1. High mechanical properties:
    The film’s mechanical properties depend on the polymers used during production and the production technique itself. At Politiv we use only the most sophisticated materials supplied by the leading producers of polymers & additives in the industry; along with fully computerized extruders. Our films meet the Israeli Standard 821, ISO as well as the ASTM (click here to view the standards certifications
  2. UV Stability (film durability):
    Film without UV stabilizers will fail after only a few months (4-6 months depending on the film’s thickness). In order to achieve the required durability UV stabilizers should be added. The type of UV stabilizers and the percentage s employed depend on the crop, film’s life time desired, area (total radiation), film’s thickness desired, type of greenhouse structure and agrochemicals used.
    When Sulfur and chlorine are used, a special UV stabilizer package should be used. it is the customer’s responsibility to inform Poly-Ag when using Sulfur and/or chlorine
  3. Maximum light transmission at the visible range (TLT):
    Energy from the sun is transmitted through the greenhouse covering to the plant where it drives the photosynthetic process. The total light transmission of the greenhouse covering determines how the photo-synthetic active radiation (400-700 nanometers) is used and this is extremely important. The intensity of these wavelengths (PAR range) directly influences thegrowth and development of green plants.

optional properties:

  1. Thermal additives (IR):
    During the day, the air in the greenhouse heats up, therefore, if you use a regular cover at night when the outside temperature cools down the greenhouse losses heat.

    To prevent extreme temperature changes, a special additive is incorporated within the film during the manufacturing process. This additive blocks the IR radiation and helps to maintain a higher temperature inside the greenhouse, thereby, helping you to deal with frost and low temperature damage.
  2. Light diffusion:
    Direct sunlight (undiffused light) can cause a “shadow” effect and “sun burns” on plants. Additives that diffuse light will cause the direct light to scatter and will prevent the shadow effect as well as the sun burns. The light diffusion increases the photo-synthetic efficiency by providing a more homogeneous light from all directions and is advantageous when cultivating self-shading plants such as cucumbers, tomatoes, squash, roses and others. The film is suitable for areas with high radiation.
  3. Anti-fog/Anti-drip:
    Hot air contains more moisture than cold air. At night, the temperature inside the greenhouse decrease, as a result, the water vapor in the air condenses and form s small discrete droplets. The effect of fog creates:
    *- reduction in light transmission with a consequent reduction in cultivation.
    *- dripping on the plants causes diseases
    In order to prevent these situations special additives are incorporated into the film. These additives modify the film’s surface so the water droplets are spread out into a continuous invisible water layer.
  4. Anti- virus:
    The human eye is sensitive to a UV range of 400-700 nm, while insects are sensitive to a UV range (less than 400 nm), therefore, by blocking the UV range, the insects inside the greenhouses are less active. As a result, less agro chemicals need to be used. Furthermore, with red roses, UV blocking prevents the roses from blackening.
  5. Anti-mist:
    Mist forms in a greenhouse when the temperature drops and the relative humidity reaches saturation. Mist has a negative impact on the plants since the leaves are subjected to a thin moist layer, top and bottom, thereby, the mist blocks out the sun’s rays for many hours after sunrise.
  6. Anti-dust:
    The multi-layer construction along with a special polymer results in a smooth film that prevents dust accumulation on the outside. This is an important feature in order to insure maximum light transmission and allows cleaning the film to become easier.

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