I just got a Univent automatic opener that opens and close a cold frame lid. I’ve wanted one for a long time. This will save me time running out and opening it on a warm fall day (so my veggies don’t cook) and then running back and closing it when it gets cold later in the day (so they don’t freeze). It is a temperature sensitive opener designed to open windows in greenhouses or lids on cold frames. It can be adjusted to start opening between 60-75°F. It fully opens at 86-90°F up to 18″ and fully closes at 55°F.
Here is a little info from ACF Greenhouses on them- “How do automatic vent openers work? Vent openers do not require electricity. The opener has a metal cylinder containing a mineral which expands when heated. This pushes a piston that opens the vent. As the temperature cools, the mineral shrinks and a spring closes the vent and resets the piston. The opening and closing of the vent is gradual allowing just the right amount of air flow for cooling.”
You can get them from ACF Greenhouses or I got mine from Peaceful Valley. Now all I got to do is get my fall greens in!
giantveggiegardener 
We have these vents on our Growing Dome and they are amazing! Word to the wise: Periodically check that the adjustable nut/screw thingie is not loose. I lost one because it worked its way off the threaded post it was attached to.
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Thanks for the advice-appreciate it!
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After looking at your univent pic, it looks like your nut/screw thingie is larger, so you probably won’t lose it! LOL!
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Hi! Looks like a great set-up. How do you get into your cold frame when you just want to open the lid? Do you have to unhook the automatic opener somehow? Does it not damage the opener to force it open? Thanks!
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It’s easy-just push a little button. No forcing.
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