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Polytunnel Polythene Terminology

There is now a bewildering array of Polytunnel Covers available in todays market, many more than when we first started selling polytunnel covers back in 2004, now over twelve years ago.

The terminology of what one polytunnel cover does over another can be very bewildering, so to try and help you decide on your polytunnel cover and what properties you need and how thick the polythene should be, we have put together a handy guide below, which will hopefully try and help you decide on which Polytunnel Cover is best for you.

Polytunnel Cover Terminology Demistified ......

If you're not sure what properties to look for in a polytunnel cover and what all the terminology means, have a read of the following....

Anti Fog / Anti Condensate :

Basically, these two terminologies are interchangeable and refer to the way the inevitable condensation forms on the inside of a Polythene Polytunnel Cover. Anti Fog / Anti Condensate Polytunnel Cover films contain a coating on the film that break down the surface tension of the water creating a fine mist which runs off down the inside of the Polytunnel Cover, as opposed to gathering in large droplets of water that then drop off the roof of the Polytunnel Cover onto your plants (causing cross contamination of diseases), as happens with none, Anti Fog / Anti Condensate Films.  It is however, worth noting that this feature does not have an infinate life span, as it is purely a coating on the inside of the film which slowly wears off over a period of about two years, although you can purchase sprays to replace the Anti Fog / Anti Condensate over the course of your Polytunnel Cover lifespan.


Thermic Films :

 Thermic Polytunnel Cover films have a dual ability to keep your Polytunnel cooler in the day and warmer during the night, aiding frost protection and also reducing heating costs. it cleverly does this by blocking near InfraRed Radiation during the day, whilst creating a barrier to the Far InfraRed Radiation reflected by the soil during the night.


Diffused Films :

Diffusers added to Polytunnel Cover Films break up the suns radiation into a multitude of rays, which gives an even spread of light across the greenhouse, minimizing scorching to taller plants and shadowing to shorter plants and decreasing phototropism (the orientation of a plant in relation to the source of light - either towards it or away from it).

Diffused films do not impair light transmission. 


UV Stabilisers

UV Stabilisers are a careful mix of additives added to the Polythene Polytunnel Film during its manufacture,  to inhibit the breakdown of the polythene under sunlight without blocking UV Radiation. The UV stabilisers also aid the stimulation of Bee, Bumblebee and other insect poination.  

Polythene films have come a long way and most manufacturers gurantee their films against UV breakdown for five seasons, with an expected lifespan in the UK of 7 or 8 years, but some customers report they have had 10 or more years use out of their Polytunnel Cover, however by this point the levels of light available under the Polytunnel Cover will have diminished and will therefore not be creating the best growing environment.

It is worth noting that the thickness of a film does not play a part in the UV lifespan of a film, as shown by Damp Proof Membrane which is usually about 1200g (gauge) in thickness but will not last 6 months under the summer sun, whilst a 720g (gauge) polytunnel film can last 10 years whilst only being almost half thickness.


UV Blocking/Disease Reducing

UV Blocking films have an additive in the film which blocks light up to approx. 380nm, this causes insects to lose visual ability in the polytunnel causing them not to fly around and therefore preventing viral and fungal diseases and crop damage caused by white flies, aphids, red spiders, leaf miners, thrips and other insects. UV Blocking/Disease reducing polythene is an effetive contributor to Integrated Pest Management.  However, NOTE : - DISEASE CONTROL FILMS SHOULD NOT BE USED IN POLYTUNNELS REQUIRING INSECT POLINATION.


Ethyl Viny Acetate (EVA) Co Polymer

EVA additives added to all Polytunnel Films increase the mechanical properties of the film, enabling it to stretch without breaking and giving it extra strength, whilst also reducing crystaline patterns in the polythene aiding transparency for increased light levels.


800g/200mu - 720g/180mu - 600g/150mu

The gauge or thickness of polythene deserves a whole page of its own, which you can find here, but to sum up the 'g' represents the word gauge which is one way of measuring the thickness of polythene, whilst the 'mu' represents the word micron which is an alternative measurement for the thickness of polythene, some sites use one measurement and other sites will use the other, or also interchange the terms.  Broadly speaking - thicker isn't always better and you can find out why here.