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Bayliss XL Greenhouse Autovent

Product Code:
£28.99 £24.16
In stock

Essential for greenhouse growing, Bayliss autovents automatically open and close hinged vents providing accurate and continuous ventilation around the clock.

Using the energy from the warmth of the sun the Autovents are designed to mechanically open the vents as the temperature increases. Similarly, as the temperature lowers so do the Autovents. They automatically open and close hinged vents. "Clip-on" model lifting a load of up to 5.5kg (12lbs) giving a maximum opening of approximately 12".

Please note that additional parts may be required to fit XL autovents to Halls, or Robinsons greenhouses.

Preparing for fitting:

Remove the autovent unit and fixing pack from the box
Place the unit in a cool place for half an hour – in a fridge is ideal. This will allow the wax in the power tube time to contract as it cools.
When the autovent unit is cool, remove from the fridge and place the steel piston rod, against a hard surface and push it firmly back into the tube. The autovent is now ready to fit.
Because the design of greenhouse vents varies considerably, it is impossible to illustrate every type of fitting. Choose the fitting method most suitable from those in the instruction booklet. To ensure that the autovent is not overloaded and that head room or growing space is not reduced. It is important that the gap between the straight link and the glass in the vent is the same at both ends when the vent is closed..


When the Autovent has been fitted, take the knurled adjuster screw from the fixings pack and slip it over the piston rod. If necessary, open the window with one hand and screw the knurled adjuster into the swivelling block until the Autovent until holds the window open 1/8 inch (3mm) when you lower it slowly take your hand away. Setting is best carried out when there is no wind blowing through the window and setting and when the temperature measured by a thermometer placed or hung on the autovent unit indicates the temperature at which you wish the vent to start opening. If you wish the Autovent to start at a higher temperature, screw the adjuster out of the swivelling block and vice versa, but make sure that at least four threads on the adjuster screw are engaged.

How it Works

The autovents strong metal tube contains a mineral wax which expands with heat. This pushes a piston which opens the vent via a balanced linkage. As the temperature drops, the wax shrinks and a strong stainless steel spring closes the vent and resets the piston.

The XL Autovent is designed in such a way that it will not open in cold weather. It is fitted with a strong spring to hold it steady, but in high winds other windows and doors should be kept closed. The XL Autovent should not be harmed by low temperatures and can even be left on the window all year round.

"Clip-on" model lifting a load of up to 5.5kg (12lbs) giving a maximum opening of approximately 12".


The unit measures 11" in length and is supplied in satin anodised finish. Complete with all the fixings and instructions.


All Bayliss products are guaranteed for two years against faulty manufacture. They are designed and tested to last for many years and are fully serviceable

When ordering just nematodes, delivery is free of charge.
For all other items, we will either charge £4.98 for standard items, £6.99 for large items and £14.99 for oversized items.
The correct delivery charge will be applied in the checkout.
*some additional charges can be applied for larger and heavier items to highlands and islands.