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Charley's Greenhouse
17979 State Route 536
Mt. Vernon, WA 98273
Fax 360-873-8264

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Solar Powered Vent Control Application Guide
Solar Powered Vent Control Application Guide

How do Solar Vent Openers work?

"Solar" vent controls convert heat energy from the sun into mechanical energy to open the vents. The hotter it gets, the wider the vents are opened.

The power comes from a cylinder with a piston inside. It contains a mineral wax that expands when heated. This expansion pushes the piston, driving a leverage arm that lifts the vent. As the temperature lowers, the wax cools and shrinks. A strong spring closes the vent and resets the piston. Opening and closing are gradual changes, allowing just the right amount of air flow cooling.

Which vent opener do I need?


Roof Vent

Side Vent


Winds over 50 mph

Gradually Opens to
Quick Release for small greenhouses

14 lbs

Streamlined for small greenhouses

14 lbs


Bayliss MK7
Triple Spring

Two extra closing springs

14 lbs

Bayliss MK7
Orchid Opener

Higher opening temperature

14 lbs

Bayliss MK7 Hydraulicheck
Hydraulic damper

14 lbs

Bayliss MK7 Super
Internal and external fins provide faster operating response
35 lbs
Mega Vent Control
Hydraulic damper & heavy lifting capacity

26 lbs

Giga Vent
Heaviest lifting capacity

33, 47, or 66 lbs
18", 16" or 12"
  • All vent openers can be installed in series to open a long or heavy vent.
  • All openers have a 2-year mfg. warranty

Vent Design

To avoid excessive temperatures in the greenhouse, it is necessary to have enough vents of adequate size. Ideally, roof vents should equal 20% of the floor area, plus lower fresh air intake vents equal to 10% of the floor area. Manual opening and closing of vents is easily done, but requires two trips to the greenhouse daily without exception. One sunny day with vents closed and plants look like last week’s salad or candidates for dried flower arranging. A cold night with vents left open will cause some plants to shiver to death and your heating system may croak from exhaustion. (Or you will croak when you get the heating bill!) So give the plants (and yourself), the care and peace of mind deserved - automate the vents!

Bayliss Solar-Powered Greenhouse Vent Controls

These “top of the line” controls will open and close greenhouse vents automatically without electricity. Bayliss vent openers convert energy from the warmth of the sun into mechanical energy to open vents. The hotter it gets, the wider the vents are opened.

Materials: Bayliss openers are made from the best corrosion resistant materials: brass, stainless steel and satin-anodized aluminum. They are designed to give many years of service, are covered by a 2-year guarantee, and can be repaired should the need arise.

Capacity: The Bayliss can exert a force of 14 lbs. at the point where it is attached to the vent. A threaded adjuster bolt can set the Bayliss to start opening the vent at temperatures between 55º F and 75º F. Maximum opening of 12" is reached at approximately 20º F above the starting temperature.

Openers can be installed in a series on a long vent to replace worn out electric vent motors. The adjuster bolt can equalize the loading so the lifters work in unison.

Installation: Easy to install with screws: top arm to vent, bottom arm to greenhouse frame. Illustrated directions included. Openers are about 12" long and fit neatly up close to the glass.