These Bayliss MK7 openers have three heavy-duty springs which gives the opener superior closing power making it ideal for side wall vents and roof vents in windy areas. Opening temperature is adjustable (Ranges shown below). Maximum opening of 12" is reached at approximately 20° to 30°F above opening temperature. Bayliss MK7 vent openers are made from the best corrosion resistant materials: stainless steel, anodized aluminum, and brass. These are recommended for use with Cross Country greenhouse vents. Powertubes are interchangeable.
Bayliss MK7 vent openers are available with 2 different models. The only difference is the operational temperatures of the powertube. The Orchid Wax model allows you to keep the greenhouse warmer in cold weather while working well in hot weather also.
Bayliss MK7 Features
- Adjustable temperature range:
- Standard initial opening temperature range: 55° F to 70° F
- Orchid Wax initial opening temperature range: 70° F to 85° F - Maximum opening of 12"
- Recommended for vents up to 18 lbs.
- Equipped with 3 heavy duty springs for windy locations
- Made in the United Kingdom
How does a Greenhouse Autovent work?
A strong metal tube contains a mineral wax which expands with heat. This pushes a piston which opens the auto vent via a balanced linkage. As the temperature drops, the wax shrinks and a strong spring closes the vent and resets the piston.

Bayliss MK7 Vent Opener Dimensions
Bayliss MK7 Vent Opener Installation Manual
Overall Customer Rating of 4 Reviews: