Simply Solar Greenhouses

Greenhouse Vent Controls

Vent Open / Vent Closed / How They Work /

Thermofax Solar-Powered Vent Controls


These “top of the line” controls will open and close greenhouse vents automatically without electricity. Thermofax 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: Thermofax vent controls 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 Thermofax can exert a force of 14 lbs. at the point where it is attached to the vent. A threaded thumb screw can adjust the Thermofax 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.



Solar-Powered Vent Openers

How they work: The opener has a metal cylinder containing a mineral wax which expands with heat. This pushes a piston that opens the vent via a leveraged arm. As the temperature cools, the wax shrinks and a strong spring closes the vent and resets the piston. Opening and closing are gradual adjustments, allowing just the right amount of air flow for cooling.

ThermoMax Auto Vent Opener

This opener is recommended for solar-powered control of top mounted window vents only. Opener is spring loaded to hold the vent snug against the greenhouse frame when closed. ThermoMax openers have an adjustable opening temperature of 59° F to 77° F and a 14" maximum opening which is reached at approximately 90° F. Lifting capacity is 15 lbs. ThermoMax openers are made from corrosion resistant materials including aluminum and stainless steel.



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