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.
End Louvre Vents
Louvres are easily fitted to the ends of the 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.
Roof Ventilation & Controller
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 fitting of these couldn’t be easier, simply cut out a 30-35cm hole in your polytunnel cover, insert the fan from the inside in a rotating motion and clip on to the support bars. It is important that the hole you make in the polythene is smaller than the diameter of the casing to create an air tight seal.
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
Circulation Fans & Control
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 Air Circulation Fans
These are purpose-built greenhouse circulation fans manufactured from Stainless steel for an attractive appearance without rust issues and long service life. They have a sealed motor unit to prevent water ingress.
| Specifications | AC04 Circulation Fan | AC05 Circulation Fan |
| Blade diameter | 400mm | 500mm |
| Voltage | 240/220 Vac 50Hz | 240/220 Vac 50Hz |
| Power | 250w (1 Amp) | 370w (1.5 Amp) |
| Rpm | 1400 | 1400 |
| Air Flow | 4350 m3hr | 5800 m3hr |
| Weight | 13kg | 13kg |
| Maximum spacing | 25m | 25m |
Variable Fan Speed Control
Simply loop the fan’s power supply through this switch for variable air flow.
| FCS15 up to 1.5 Amps |
| FCS30 up to 3 Amps |
| FCS60 up to 6 Amps |
Temperature Controller FCP02
This precise temperature controller is the ideal partner to any of our air circulation fans, allowing for maximum economy and temperature control. It can also be configured to work with heaters in winter.
- 1 Single temperature dial control
- From 0° to 30° control
- Temperature sensor on a 25m cable
- Thermostat for heating and cooling
- Splash proof IPX4
- Fan appliances output load 1kW inductive
- Heater appliances output load 3kW resistive
- Can run up to five 200w fans or one 3kW electric heater
Side Vent Options
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.
Side Vent Automation All our side vent options are able to be fully automated, with or without temperature control.
Economy Range Side Vent
Our entry level side vent. This system is available for polytunnels with timber side rails. The polythene screen and exterior netting are battened on to the side rails using wooden laths. The screen on this vent is polythene and clips directly onto a steel drive tube and is raised or lowered with a manual gearbox. There are no draft panels.
Commercial Timber Range Side Vent
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)
Commercial Aluminium Range Side Vent
Our superior range side vent with a manual gearbox operating the internal roll-up PVC screen. This system is available for polytunnels with aluminium side rails. The polythene screen and exterior netting are connected to the side and base rails using wiggle wire. 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)
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Economy Range Side Vent |
Commercial Timber Range Side Vent |
Commercial Aluminium Range |
| Base Rails | Base Rails | Timber | Aluminium |
| Side Rails | Timber Side Rails | Timber | Aluminium |
| Battens | Timber Battens | Timber | N/A |
| Shade | Full Depth shade net only (no skirt) | Full Depth net with PVC skirt | Full Depth skirt to net |
| Gearbox | Manual | Manual | Manual |
| Curtain Tube | Steel | Aluminium with Keder Slot | Aluminium with Keder Slot |
| Curtain | Wind-Up Polythene Curtain | Wind-Up PVC Curtain with Keder | Wind-Up PVC Curtain with double Keder |
| Draft Panels | Included | Included |