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Guidelines

GUIDELINES FOR THE USE OF GREENHOUSE COVERING SHEETS

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HANDLING AND STORAGE OF THE ROLLS

  • As the sheets thickness is limited to 1-2 tenths of a millimeter and even less, particular care should be taken when loading,
    transporting, unloading and stocking, making sure not to drag the rolls on the ground.
  • The rolls have to be stored in a shaded, dry place and left in the original wrap till installation, paying attention at the presence of
    rodents.
  • The rolls should not be stored for more than 12 months before usage.

INSTALLATION

  • Avoid to install the film during the warmest hours of the day (in summertime risk of loosening the film), in particularly cold periods
    (in wintertime difficulty of film tensioning and potential problems with the anti-fogging system), and in any case in windy conditions.
  • Do not leave the film unrolled or folded in the sun without the original wrap, even for a short time, nor outside when there is a risk of
    frost.
  • While unrolling the film, check the contact surface (ground or structures etc.) to avoid contact with sharp edges or abrasive
    surfaces.
  • The film should be properly tensioned , it should not exceed 3% of strain in either direction. This avoids the formation of wrinkles or
    hollows, the flapping due to windy conditions (insufficient tension) and the reduction in the thickness of the sheet where it is held in
    place (overstretching).
  • Check that the gutters are properly sized and without obstructions (risk of hollows).
  • It is advisable to stop small holes, tears or cuts from running or expanding using a suitable repair tape.
  • When dealing with air inflated double sheets, always fit an outside air intake and limit the air pressure to 6mm (¼’’) water column.
  • Don’t cut or tear the sheet during the handling and the installation. It is possible to make round holes or opening with rounded
    corners only.

WOOD GREENHOUSES

  • When using the film on wood greenhouses, it is essential to smooth off or remove any sharp edges which might damage the film.
  • Avoid to install the film on resinous wood or wood treated with protective substances which might cause the film degradation
    (naphtha, tar coatings, sulphurous solutions, solvent-based paints etc.).
  • Installation on black wooden frames or any other black or dark material or on PVC accelerates the rate of local degradation of the
    film.
  • In case nails are used, sandwich the film between two pieces of lath by putting nails every 150 – 200 mm.

METAL GREENHOUSES

  • The film must only be used on galvanic zinc coated steel structures.
  • Do not install on rusty metal structures that could damage the film by abrasion and by chemical degradation process.
  • When using the film on new structures, make sure any residual traces of grease, lubricating oil or organic solvents are carefully
    removed. Also when the structures have been left open to the atmosphere or stored for a long time (even some months or more)
    make sure they are carefully cleaned before installation.
  • Corners and edges should be rounded off or protected and any metal burring which could cut or damage the film should be
    removed.
  • The contact surface between the film and the frame should be protected using white acrylic or vinyl paint applied to the external
    surface of the covering. This protects against early degradation of the film due to thermal action (high temperatures in the points of
    contact between the film and the metal frame of the greenhouse). For the same reason, avoid solarization techniques once the
    covering has been installed.

LIFESPAN OF THE FILMS

  • The warranty period starts from the date the film is delivered, unless otherwise agreed.
  • Thickness: film thickness should comply the PATI dimensional standards and EN 13206, 2002 standard where applicable.2/2
  • Lifespan indications are always based on tests carried out in conditions according to EN 13206, 2002 standard.
  • The quoted film life is always referred to installation performed in Autumn. When the film is installed in other periods of the year,
    the user should contact the producer to verify the expected life reduction.
  • Extensive research performed by leading manufacturers of additives shows that UV stabilizers included in plastic films can be
    inactivated by several categories of plant protection chemicals with a consequent reduction in stabilizing effect (lifespan of the film
    lower than expectations cfr. APPENDIX A EN 13206, 2002 standard).
  • The lifespan of films is related to a number of factors, for example, but not solely, proper installation, design and structure of the
    greenhouse, protection of contact points, latitude, climate factors, type of crop and relative treatments (type, frequency and
    technique of application of plant protection chemicals).
  • Plastic film is stabilized only against degradation caused by sunlight. The user should therefore take particular care when using
    sulphur, chlorine, bromide, iron, copper, aluminium etc. which, on contact with the film, can accelerate degradation, especially in
    areas where such substances are collected or accumulate (winding pipes, fastening profiles, gutter edges, laths etc.).
  • Tips for limit the interactions between harmful chemicals and the film:
  • when using said treatments, be sure to follow manufacturers’ instructions regarding dilution, supply pressure and settings of
    the spray nozzles, and limit the use of foggers, guns and sulphur sublimation systems inside the greenhouse;
  • avoid contact between the film and crops;
  • always provide good ventilation of the greenhouse;
  • do not burn sulphur, PVC or other materials inside or close to the greenhouse;
  • If it is necessary to shade the greenhouse during the Summer, use only products or materials specifically designed to this purpose
    only.

ANTI-CONDENSATE TREATMENT

  • Thermoplastic films promote an increase in evapotranspiration of crops, with an increase in the relative humidity inside the tunnel
    or greenhouse, which can, in consequence, cause fogging, increase in condensation and/or other phenomena which are difficult to
    predict as they depend on other factors and chemical substances, as the ones mentioned above, which also influence the lifespan
    of the film as well.
  • Anti-drop additives reduce the surface tension of condensed water creating a continuous thin layer of water avoiding droplets,
    only if the film has been properly installed with its side marked INTERNO/INSIDE facing the greenhouse inside.
    However, due to the number of factors which may influence the effectiveness of anti-drop additives, there are no guarantees
    regarding efficiency in reducing droplet formation, or regarding the continuing duration of the effect.
    Factors which may reduce the effectiveness of anti-drop additives are mainly, but not solely:
  • very warm season, causing an excessive migration velocity of the additive;
  • very humid or rainy season when the additive washes away too quickly;
  • very cold season, which can reduce the effect by inhibiting the migration of the additive onto the film surface;
  • particularly intense irrigation of crops (due to seasonal weather conditions), which increases evapotranspiration;
  • insufficient air recycling inside the greenhouse;
  • insufficiently covering film slope which does not allow condensation sliding down.

IMPORTANT WARNING
This information represents the current extent of our technical knowledge and is intended as a guide to our products and to
their most effective use. It does not constitute any form of guarantee of the results which may be obtained. In particular, no
guarantees are made regarding agronomic results, for example, but not solely, ripening or maturation times, yields or quality
inasmuch as these results are conditional on climatic, pedological, fitopathological and environmental factors in general, as
well as the cropping techniques applied.

PATI reserves the right to modify this information in line with advances in technical knowledge of the subject.