Automatic Vents for the Greenhouse

. . . Automatic Vents: Circulation for the Greenhouse

Automatic greenhouse vent openers work on a pretty simple principal. As wax (or a similar substance) heats up inside a cylinder, it expands and pushes a piston out. The piston then pushes open the vent or window. Most openers begin to expand at 70 to 75 degrees Fahrenheit. Some automatic vent openers are adjustable as to how far they will open or sometimes even at what temperatures, although 60 to 75 degrees seems to be the average "adjustable opening temperature." Of course these automatic vent openers were created specifically for greenhouses, but many are easily installed in ordinary fold-out windows. Many automatic openers include springs to pull the window closed tightly after closing and are rated for how much weight they can lift. This was important as I installed these on windows with hinges that folded up. My opener bears the weight of the entire window when it opens.

. . . for Monitoring Greenhouse Temperatures

Greenhouses can get extremely hot quite fast. If you aren't able to open and close the doors or windows on a pretty regular schedule, you may find yourself frustrated with how to keep it from getting too hot. One hot day in my greenhouse means my tomatoes endure 120 degrees Fahrenheit! On days the clouds keep the sun from heating up the greenhouse, I don't want my door open, but on days the sun is up and bright early, I have to be quite diligent to get out there and open the doors and windows before it gets too hot. My solution for this was to purchase two automatic vent openers, which cost about $50 to $80 each but are very much worth the money if you aren't able to run open the greenhouse door any time of the day. It's also saved my tomatoes a few times when I left while the sky was pouring rain but wasn't home in the afternoon when the hot sun came back out!

. . . for Monitoring Greenhouse Humidity

It's important that greenhouses have ventilation. Plants not only need adequate air for respiration but too much humidity in a greenhouse can cause damp conditions that often lead to problems. Circulating the air is helpful and automatic window openers allowed me to circulate dry air from the outside through my greenhouse.

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Location of the Automatic Vent is Important Consider where to install a greenhouse vent, as you want it to circulate air and, depending on the size of your greenhouse, it shouldn't open too soon (at least in Montana). I have an automatic window opener on each end of my greenhouse, one down low and one up high to help circulate the air through my greenhouse. Often the one up high will open sooner or may be the only one that opens completely for the day.

Maintenance is also Important It is recommended you remove cylinders in the fall so they do not freeze and reinstall in the spring, though cylinder replacements are available. You should oil moving parts (including the cylinder rod) once a year with a light oil or Teflon spray.

Univent and Gigavent are two major brands of automatic vent openers for the greenhouse.