Greenhouse automatic vent opener in the open position

How to Keep Your Greenhouse Cool With Automatic Greenhouse Vent Openers

Greenhouse too hot? And you forget to open the greenhouse vents again!? With automatic greenhouse vent openers, stop overheating your greenhouse for good.

Greenhouses are designed to capture solar energy. But too much of the sun’s heat can be a problem.

The sun is a powerful source of energy and a small greenhouse can reach blistering temperatures in just a few hours.

The last thing you want to have happen is for your plants to perish because they literally were cooked.

The easiest and most reliable way to avoid this is to install automatic greenhouse vent openers.

Why You Need Greenhouse Vents Or Windows

blazing sun in blue sky

Greenhouses need to be designed to not only capture solar energy but also adequately ventilate excess heat if temperatures get too hot.

You should always make sure you have adequate vents in the roof of your greenhouse as heat rises and you want that heat to escape.

Greenhouse roof vents work really well as they are located where hot air gathers naturally at the peak of the roof.

If vents in the roof are not possible, make sure to at least have a window to two you can open.

Ideally you want to have cross ventilation so two windows on two sides of the greenhouse work best.

However you should not leave the vents or windows open at nighttime as you’ll lose any heat gain and cool your greenhouse too much.

So you close the vents or windows at night and what happens the next morning: you forget! Now your greenhouse overheats and if you’re unlucky, you lose some plants.

Or you forget to close the vents at nighttime and your plants suffer if the night is too cool.

Instead let’s automate your vents and windows using automatic greenhouse vent openers. Set them and forget them.

Electric Vs. Wax Charged Automatic Vent Openers

There are essentially two types of automatic vent openers. One uses an electric motor to open the vent and another one using wax charged cylinders to hydraulically open the vent.

Electric Greenhouse Vent Openers

These use a strong electric motor to open the windows in the morning and close them again at night. They require an external temperature sensor to tell them when the temperature reaches a preset level.

Since you have to rely on a power supply, whether it be batteries, solar panels or line power to power the motor, if anything goes wrong with the power source, the vents won’t open or close.

Therefore as a failsafe, most systems have a power backup of some sort for all the vents or have some vents powered by one system and the other vents powered by a second system.

Non-Electric Automatic Vent Openers

These rely on a expandable wax (usually beeswax) that expands when heated and contracts when cooled. This pushes a hydraulic cylinder to open the window. The cylinder is similar to what you find on a car’s hatchback or tailgate.

As the temperature decreases and the wax cools, the hydraulic window opener contracts and a spring pulls the window or vent closed.

The main benefit is that they do not require an external temperature sensor and are adjusted with a thumbscrew to set the temperature at which they open and close.

So they’re a bit more reliable than an electric system since you’re not relying on an external power source or an external temperature sensor.

They can however fail if the seal on the cylinder leaks or in my case the thumbscrew on one kept turning by itself and I had to jury-rig something to stop the screw from turning.

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Advantages Of Automatic Greenhouse Vent Openers

I’ve alluded to some reasons why you should consider these types of openers:

automatic greenhouse vent opener from inside a greenhouse
  • Don’t need a long pole or ladder to open the vents
  • Don’t need a manual way to prop the vents open
  • Can be adjusted to open when greenhouse temperatures hit a certain threshold
  • Open automatically during the day – great in summer if your mornings are still on the cool side and you’re not home to open them later
  • Will stay closed if you have a cloudy day that doesn’t warm up your greenhouse enough
  • Close automatically at night when the temperature drops
  • Will stay open if nighttime temperatures do not drop sufficiently

My Buying Recommendation

The automatic vent openers do cost some money.

But in the end you can save a lot of money by not having to replace plants that perish when greenhouse temperatures hit extremes because you forgot to open the vents manually.

And they save you a lot of time not having to open vents in the morning (or later in the day) and close them again at nighttime. And they say time is money!

I don’t recommend getting an electric vent opener. They are more expensive, require additional equipment such as a power source, temperature sensor and wiring and are not as reliable as motors can burn out or wires can break or power supplies can fail.

So the best automatic greenhouse vent opener I recommend that is cost-effective (mine were expensive!) and has good reviews is this one:

If you prefer to buy in person you can probably also find them in a well-stocked feed supply store or greenhouse supply store. But you may find them to be much more expensive as they were catering to greenhouse growers.

The good thing is that these commercial openers will usually be of much higher quality and open much larger windows and vents.

You Need Some Type Of Backup

greenhouse roof with three vents, two of them open

I recommend having at least two automatically controlled vents just in case one of the vent openers fails. I have three and wish I would have added more (and I may at some point).

I also open my greenhouse door in the morning for added ventilation. And I have my solar-powered fans help move the air in the greenhouse. I describe how I installed in this post: Free Greenhouse Ventilation Via Solar Panel

For electric vents you need to have two sources of power. But again you need to have more than one vent as wiring or motors can fail, especially in the hot, humid environment of a greenhouse.

Automatic greenhouse vent openers will pay for themselves in reduced plant damage and save you the time and effort of opening vents manually.

For an expanded list of greenhouse accessories that I recommend all greenhouses to have, check out the post 7 Greenhouse Accessories and Features That Get You The Best Results

Want even more greenhouse information? Check out my greenhouse playlist on YouTube: Greenhouse Growing

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