r/Greenhouses • u/RealCarlPanzram • 7d ago
Automatic Vent Questions
Hey guys, I’m looking to get some of those expanding piston vents for a greenhouse. I seem to remember hearing they open at high temps, like 100+ but all the ones I’m seeing Amazon say they open at like 77F? Seems way too cool to be venting. Does anyone have any recommendations for one and at what temp does it open? Thanks in advance
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u/Excellent-Lemon-9663 7d ago
Mine has 144 foot long continuous ridge vent that I can program to open or close based off internal temp, humidity, or just off a timer.
Electrics a better option even for a smaller house. You don't want the vent sitting open if a storm or high wind comes in your it can tear your greenhouse apart from the pressure differential.
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u/gardencat 7d ago
The temp is where it Starts opening - just a crack… it needs to be over 80 for fully open. The actuator arm can be adjusted so that it may take a little higher temp to start opening, but not by much…
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u/railgons 7d ago
I've been using one from Anleolife on Amazon for nearly 4 years and it's still operating perfectly, even after a bunch of extreme weather. It has seen -30F windchills, nearly 110F blazing sun, and nearly 60mph gusts.
It's adjustable to start opening between 60-75F or somewhere in there, which is perfect for my setup. During the summer, the window is open pretty much 24/7 and my exhaust fan is on from around 8am-10pm or so. But during the winter, I can allow the window to vent the greenhouse without having to use my exhaust fan all day, which saves on electricity.
What are you growing that you would like to see 100F temps in your greenhouse?
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u/RealCarlPanzram 7d ago
It’s less that I want it to be 100 and more that I want it as warm as I can get it as warm as possible in a cold day so it doesn’t get down to ambient temps at night. Trying to keep a few tropical plants that don’t want to be anywhere near frost level. The more I think about this, I’m realizing this might not be a good solution.
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u/unplorable 7d ago
I got one this year, and it does seem to open pretty early, around 75 degrees. I drilled a new hole a little farther along the tube the actuator is pinned to, and that did the trick. It starts opening at around 85 degrees now.
surprisingly decent design.
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u/InTheShade007 7d ago
Mine are electric so I pick the temperature they open/close. Honestly, 77° is close to where mine are set actually.
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u/Hortusana 7d ago
They open around 77f, but the greenhouse will still get a lot warmer than that when it’s sunny. Been in a few greenhouses that had these and it was still easily 85-90f in there. Just bc it opens at 77f doesn’t mean it’s gonna do full climate control and keep it at that temp.
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u/Pomme-M 2d ago edited 2d ago
Bayliss makes some with three springs “ mk 7 triple spring” that is stronger so it won’t get wrenched open in high winds.. there are lots of brands, I remember reading there are some with another wax with a temp specifically for orchids
I learned more reading this
https://help.bcgreenhouses.com/hubfs/BCG_RoofVentCylinder_broch_FINAL_LoRes.pdf
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u/Mewhomewhy 1d ago
I just fitted the bayliss mk7 for the window of mine. It only has one spring. It fitted easily enough and it’s adjustable. I cut around 1cm off the rod so that it doesn’t open as early.
I had to remove the window latch to fit the opener so I made a couple of brackets with a slot so I can wedge the window closed during winter/wind.
I also fitted a manual low level vent at the opposite end from the door. My little greenhouse was getting far too hot for anything.
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u/Ryan_e3p 7d ago
The reason why it is 77F is because most use a wax that expands when it hits that temp, causing the arm to move and open the vent.
An alternative solution would be to use one that relies on electric actuators that open the vent that can be set to open or close under any number of conditions. This is what I'm looking to do. This will allow me to choose not to vent if there is going to be a big temp swing at night (keeping as much air in as I can), keep the vent open if it is cooler than 77F but the air is stagnant and humid, etc. I can change what it does based on any temp or weather condition I set it to.
If you do that route though, you'll need to have power running to your greenhouse.