Your first big decision when choosing a Polytunnel is almost always..."What size is ideal?". But there's other important factors to take into consideration..."What type of cover do I want?". It might not sound like something to give a lot of thought to, but the cover you choose will affect your day-to-day Polytunnel management, what and how you grow. We have 4 options to choose from...

Super Therm

Super Therm PolytheneOur most popular polythene cover incorporates an additive that increases its Thermic efficiency, yet still retains 90% light transmission. In simple terms the polythene helps trap and preserve higher temperatures inside the structures for much longer - in heated structures, a 15-20% fuel savings can be achieved. A beneficial side effect of this added additive is that light entering the polytunnel is diffused - scattering light evenly throughout the structure. This UV stabilised film is 200 microns (800 Gauge) and is supplied with a five year guarantee.

FOR USE WITH All crops where heat is important such as bedding/annual plants, propagation houses & over wintered vegetable production.

Super Therm Properties

Solar Radiation

Our polythene is exclusively sourced from Sotrafa in Spain, the world's biggest producer of horticultural film with an enviable reputation for quality thanks to exhaustive testing in the demanding weather conditions of Almeria.

First Tunnels are the sole distributor of Sotrafa products in the UK, and we are proud to work with the global leader to deliver the best possible products for our customers. UK suppliers make cheaper alternatives, but the quality simply doesn't compare.


Solar Radiation

Although guaranteed for 5 years against its biggest threat of sunlight degradation, when fitted correctly, it is not uncommon to hear our polythene covers have lasted in excess of 10 years.

5 Year Polythene Guarantee

Please note - to help identify the polythene type and validate the guarantee, a series of numbers and letters are intermittently printed across the polythene.

View the terms of the Guarantee here.

Sunlight is the biggest enemy of polythene. While it's essential for the wellbeing of whatever you're growing, it also 'kills' polythene in much the same way you can find old discarded crisp packets lose their colour and become very brittle. First Tunnels polythene covers are developed and tested in the extreme conditions to give optimum performance and are UV stabilised to prevent the polythene from breaking down prematurely.

What is a KLy?

A Kilo-Langley is the measure of Solar energy radiated in 1 year. It varies from a minimum of 60 KLy in the Polar regions to 120 KLy in warm regions, and to a maximum of 200 KLy in the African desert. Southern Spain receives about 140 KLy whereas the UK receives about half of that, just 78KLy.

Solar Radiation


Our Super Therm polythene is 800 gauge/200 micron and made up of 3 layers for outstanding strength and performance.

We use a 3 layer polythene made of exceptional quality material, which has a hugely beneficial thermal effect.

The common misconception about polythene is the more layers, the better the product. Unfortunately this isn't true. More layers simply hide poor quality films, which are sandwiched inside a very average inner and outer skin. 25% ThickerThe result of these multi-layer (often called 5 or 6 layer) films is a noticeably poorer all-round performance - the thermal effect is significantly decreased.

Total Transmission of Visible LightTotal Transmission of Visible Light
The amount of available light entering the polytunnel through the film. Measured as a percentage of total light.
Super Therm = 95%

The scattering of direct light entering the polytunnel ensuring no shadows, so all plants receive equal light. Measured as a percentage of total light.
Super Therm = 30%

Thermal EffectThermal Effect
A pocket of additives within the layers of the film that ensure and maintain a stable and optimum temperature within the polytunnel, especially during the night when it is colder.
Super Therm = 85%

Strength at BreakStrength at Break
The load on a tested sample when it breaks. This is expressed in Pascals or MPa.
Super Therm = MD24/TD23

Elongation at BreakElongation at Break
The strain on a tested sample when it stretches. This is also expressed in Pascals or MPa.
Super Therm = MD920/TD920

As the weather changes becoming hotter or colder, so the Polythene expands and contracts. Creep is the terms used to express this.
Super Therm = 5

Dart TestDart Test
A test to measure the impact strength on a test piece of plastic, using a weighted falling 'dart'.
Super Therm = 5