Ventilation is one of the key elements to growing succesfully in any type of tunnel. When you cover plants with glass or polythene you remove many of the unwanted elements such as rain, wind and frost. Eliminating these can allow you to grow a better crop. But conversely during the warmer months, if a tunnel is not properly ventilated you can soon 'cook your crop'. This is why all our tunnels come with ventilation fitted as standard to allow you to regulate temperature.

On the Haygrove Garden tunnel we have a side venting system that is stitched into the materail on either side. . 

Vents are roll-up, roll-down. Fully opened the vent is 0.8m (2’6’’) wide or the vent can be stopped at any width to allow less cooling especially in early spring and autumn.


Insect Control

Stitched under the vent is an insect net. This means that when the vents are lifted the fresh air can come into the polytunnel, but the pests can't.

The insect net has been specified to a mesh size that will prevent common pests such as whitefly, thrips and aphids getting into your Garden Tunnel.

Frost Protection

There are a number of important techniques to protect your Garden Tunnel plants from frost and to extend the growing season.

Sealing the Tunnel

The Haygrove Garden Tunnel has been designed to be fully sealed for winter and early spring protection with no air gaps or holes for warm air to escape.


  • The door has been designed for the outer frame to overlap the inner frame to create a great seal. In addition, the door comes with a draft extruder fitted around the edge of the frame to provide a good seal.
  • The steel skid at the base of the structure incorporates a channel that zip locks the plastic into the frame to make an excellent seal around the complete base of the polytunnel.
  • To seal the side vents the Garden Tunnel comes complete with special clips that means the edges of the side vent can be completely secured to the steel structure during the winter and early spring.

Adding Extra Frost Protection

Your Haygrove Garden Tunnel with well sealed sides, doors and base should provide up to -3 to -4°C frost protection.

However, it is also possible to achieve added protection. Here are a useful list of techniques:

  • Add woven fleece material inside the tunnel. This can be achieved by laying the fleece material directly over the plants or better still creating a ‘false ceiling’ by running wires from hoop to hoop inside the tunnel and draping the fleece across the wires and down the sides to create in effect a double glazed house.
  • Add a Greenhouse Heater. There are a vast range of electric, gas and paraffin heaters on the market. A typical 1.8kw Electric Greenhouse Fan Heater will heat approx. 6 sq m (65 sq. ft) or provide frost protection for 12 sq m (130 sq ft). To create a confined area inside the Tunnel to apply heat, it is easy to drop a plastic baffle from inside one of the hoops to create a false walled compartment.


Depending on where your polytunnel is located, green algae can build up.

This blocks light entering the tunnel and limits the growing potential of your plants. To clean your tunnel, wash with soapy, water and a soft brush. 

Replacement covers are available if your cover is damaged or has begun to degrade, usually after about 8 years.