Polythene film: Diffused or Clear?

Light Transmission

• Light transmission is the quantity of light going through the polythene, measured by %.
• For temperate climates, a rate of higher than 85% is the target.

Thermal Efficiency

• Where the heat in the tunnel is retained during the night.
• This is measured by thermal retention + thermal transmission = 100 and is expressed as %.
• The higher the thermal efficiency, the better the polythene retains heat.
• The higher the thermal transmission the more energy is lost.

Anti-Drip

• The anti-drip coating reduces condensation droplets and produces more of a film of water.

Benefits of Anti-Drip

• Reduces the risk of droplets then dripping which can cause fungal diseases.
• Improves the quality of light for photosynthesis, Droplets of water cause light refraction reducing the quality of light.

Note: requires adequate management of the internal micro-climate through ventilation.

Lumisol Clear – Clear Polythene

The clear polythene improves the passage of light into the tunnel to promote photosynthesis.

Clear polythene is measured by haze. The lower the % the clearer the polythene appears and the more light is allowed to be transmitted.

• Our clear polythene has 30-35% haze.
• Our clear polythene has 88-92% light transmission.
• Our clear polythene has 80-85% thermic effect.

Benefits of clear polythene:

• Improves the quantity of light to encourage photosynthesis.
• Encourages early crop yields and crop strength.
• Increases daytime temperatures.
• 5-year incremental guarantee, although a 12-14 year lifespan is not uncommon.

Lumisol Diffused – Diffused Polythene

The diffusion effect ensures better light distribution inside the polytunnel, Diffused Polythene is measured by haze.

The higher the % the cloudier the film is, the more light it defuses.

• Our diffused polythene has 90-93% haze.
• Our diffused polythene has 87-91% light transmission.
• Our diffused polythene has 80-85% thermic effect.

Benefits of diffused polythene:

• Reduces the stressful effect of direct sunlight on the plants.
• Reduces the risk of leaf burn and crop deformation.
• Encourages a more uniform ripening and colouring of the fruit as less shadowing is cast. Note: designed for use in very luminescent areas of the UK.
• 5-year incremental guarantee, although a 12-14 year lifespan is not uncommon.

Over a certain length, commercial tunnels can struggle with stagnant air in the middle of the structure that airflow from open doors cannot circulate.

The best recourse for this is to opt for side ventilation. Whether manual winch, gearbox or motor-driven, it gives the grower control over the environment in the polytunnel.

Opening the side vents allows air to flow throughout the tunnel reducing hot spots in summer. Closing them during cooler months reduces heat loss and encourages the grower to bring on plants earlier in the year.

Side vents are designed work in conjunction with open doors and/or roof ventilation, allowing full circulation through the tunnel.

Commercial Timber Range

• Timber Base Rails
• Timber Side Rails
• Timber Battens
• Full Depth net with PVC skirt
• Draft Panels
• Manual Gearbox
• Aluminium Curtain Tube with Keder Slot
• Wind-Up PVC Curtain with double Keder

This is our professional range side vent with a manual gearbox operating the internal roll-up PVC screen. This system is available for polytunnels with timber side rails.

The PVC screen and exterior netting are battened on to the side and base rails using wooden laths. The netting comes complete with a solid draft-proof skirt, draft panels are also fitted to the mesh where the curtain ends to minimise the cold air entering the tunnel. The PVC Screen fits inside the aluminium drive tube using a Keder bead and is raised or lowered with a manual gearbox. (An automation option is available)

We only offer sliding doors on our commercial tunnels. Over the years we have learned that doors on polytunnels work better and last longer if they slide rather than swing.

We offer 2 models; a low-cost timber framed, clad in polythene and our new heavy duty aluminium frame, clad with PVC. Both versions come with our aluminium profile sliding track and 4-wheel roller carriages.

Low-cost Timber Doors

• 3” x 2” timber with fixing battons
• Polythene cover
• Nail plate joints
• NP door furniture Door shoes fixing to the posts, drop bolt at the back of the door, door catch, small channel to hold the together when shut.

Heavy Duty Aluminium

• NP designed aluminium door profile with wiggle wire fixing system
• Clear PVC top panel
• PVC grey lower panel
• Steel, bolt on triangle corner plates
• PVC finishing strip to cover the perimeter wiggle wire
• Brush strip seal at the rear of the door (optional)
• NP Designed door furniture, Door shoes to fix to the door posts, drop bolt at the rear of the door, full length channel section to form a seal between the doors, door catch.

Louvres are easily fitted to the ends of our structures. They can be used in conjunction with doors and the configuration can vary, depending on the size of your structure.

Louvre measurement: 0.79m x 2.12m.
Actual ‘opening’ size: 0.8m x 2.15m.

Ventilation Louvres – Pull Cord (Gable end instead of a door)
These feature our unique 3 positional hinge which locks the louvre in place. This allows the louvre to be set in the fully open position, (90°) 1/2 open (45°) or closed. These can either be single row or a double row (as above) for extra ventilation.

Ventilation Louvres – Rack and Pinion (Above the door)
These louvres feature a rack and pinion system for opening, controlled by a gearbox with winding handle. The rack and pinion louvres are fully adjustable, not just limited to the three positions like the pull cord louvres.

It may seem like an obvious statement, but the more steel in the structure, the stronger it is. How much steel you need can depend heavily on the prevailing weather in your area. You can use the maps and tables included in this brochure (page 6) to check your average wind speed and snow load. This will help you to determine which kind of crop bar hangers you should choose; the “Inverted V” for lighter weather loading, or the sturdier “W-Hangers” for heavier weather loading, load bearing apparatus and crop support.

Formed from 50mm and 32mm diameter, Armour-guard coated steel tubing, our crop bars and hangers are just as strong and durable as the hoops they service. Not only do they pin the hoops together, they prevent lateral movement and joint loosening. When fitted with “W-Hangers”, they’re strong enough to carry direct loading. This is often seen in retail locations where large numbers of hanging baskets or planters are to be displayed. Crop bars also form the backbone of vital irrigation and air circulation systems as they are able to carry the additional load of water pipes, heaters and fans.

Our crop bars are just another reason why Northern Polytunnels produce the most robust tunnels on the market, specifically designed to stand up to the worst that the British weather can throw at them.

V Hangers – Sufficient throughout most of the UK

W Hangers – Used in more extreme locations on wider tunnels

These roof air extraction fans have revolutionised the way that polytunnels can be ventilated. These fans extract heat from the roof space of the greenhouse at its highest point. Which, in turn, draws cooler, fresher air in from the doors or side vents creating air movement in the structure. The 240v fans can be connected to either a simple on off switch, one of our fan controllers or a climate computer.

The number of fans required depends upon the volume of warm air you want to expel and how quickly you want to expel it. As a general guide we would recommend a maximum of one fan for every 350m³ of air space – this would allow up to 13 air changes per hour.

Typically, one fan would be required for every 35ft to 80ft of polytunnel, depending on the width, height, and existing ventilation systems. For a 30ft (9.14m) wide polytunnel this would be approx. 1 fan for every 36ft (11m) length of polytunnel.

Therefore, a 30ft wide x 110ft long polytunnel would require a maximum of 3 fans. Even if only a single fan was installed you would still feel a significant difference as you would still achieve 4-5 complete air changes per hour.

Fan Controller

This precise, adaptable and dependable temperature controller is the ideal partner to any of the air circulation fans offered in our brochure, allowing for maximum economy and temperature control.

This robust unit can also be configured to work with heaters in winter. It’s a fantastic way of keeping simple, but accurate control over your growing environment.

• Function for ventilation in summer
• 1 Single temperature dial control
• From 0° to 30° control
• Temperature sensor on a 20m cable
• Fan appliances output load 1kw inductive
• Can run up to five roof fans
• Splash proof IPX4

Optimal ventilation is vital as it plays a significant role in the cultivation of crops. Effective air circulation not only supports but drives crop growth and gives the grower complete control over the climate inside the tunnel.

Mould and fungal diseases thrive on poor ventilation, which is why proper air flow is so important.

It’s not all about the heat. On a humid and sunny day, when the temperature inside the greenhouse rises excessively, it’s important to open the vents to avoid overheating and to spread that cooler air evenly throughout the tunnel. This can be achieved using circulation fans throughout the structure.

NP overhead irrigation kits utilise the best components we can source including VDL valves and pipework, Netafim down tubes, anti-drip valves and nozzles giving high spray uniformity with minimal wasted water.

Our kit includes 30cm weighted down tubes, anti-drip valves and a nozzles/sprinkler specific to each width of greenhouse, twin 32 mm PVC spray-lines with PVC ball valves on each line, these are connected to a 50mm PVC header manifold with a drop pipe and connection for a Geka snap coupling.

All straining wires, tensioners and header brackets are included in the kit.

Sprinkler Performance

Each sprinkler is connected to a weighted 30cm down tube this allows the sprinkler to work in a true plumb position for optimum performance.

These are connected to a pressure release anti drain valve, these prevent the water within the sprayline dribbling out after a watering period has ended, saving water and leaving the line ready and primed for the next use.

Benching

Our robust cost-effective benching system is modular meaning that its easily dismantled and reassembled to expand or reduce in size.
The benching comes as a flat pack which is easy to re-site or store when not in use.

The construction is based on our ArmourGuard 25mm diameter tube which has a magnesium zinc coating for years of rust-free life. Our specially designed corner and side fitting gives the bench its modular capability and strength. It is supplied with four corner bracing bars to give extra stability.

The bench top is a hot dipped galvanised mesh with a 3mm wire diameter and hole size of 25mm x 75mm.

Available in 1mtr wide and in multiples of 1.2m lengthways, allowing you to create a continuous bench to suit the length of your polytunnel or plant display area.

Staging

Our staging kits are a low cost solution where a full length bench is required for your polytunnel.

We ONLY provide the steel frame, leaving you to provide your own table-top. Some customers use heavy-duty, galvanised weldmesh, whereas others choose timber slats. Whatever your choice, our staging kits provide the ideal framework on which to grow your potted plants. Supplied with fasteners for fixing timber slats.

Our staging can be installed in new and existing polytunnels.

The Danish Trolley track and ramp is easy to lay and move, and can be used as either a permenant or temporary track. The interlocking sections (end to end) ensure smooth and quiet trolley movement and are supplied in 1.2m x 0.54m interlocking lengths. The track is heavy-duty,long-lasting and made from recycled plastics, with a built-in anti-slip surface along the centre.

Quantity = length of the tunnel ordered

With less than 5% light transmission, ground cover is an effective weed control fabric. Manufactured from black polypropylene (100gm/m2) with 25cm x 25cm green grid lines for accurate plant spacing.

Optimum water permeability (15ltr/m2/second). Ideal for above-ground or below-ground applications.