Last updated on April 27th, 2021
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Do you run out to your greenhouse in your pyjamas in the morning when the suns up to open the window so the plants don’t cook in the hot air inside? When you’re away, are your neighbours reluctant to constantly open and close your greenhouse door when the temperature changes? An automatic vent opener takes the worry and personal time and effort out of ventilating your greenhouse and they are well worth installing. Fitted to a window (usually in the roof), automatic vent openers open the window when it’s hot in the greenhouse and close it when the weather cools off.
This review of the Best greenhouse automatic vent openers for controlling the temperature in your greenhouse introduces you to the best models of this product to help you avoid cheap copy products that simply underperform or break.
We describe the features of each greenhouse automatic window opener and its pros and cons. We end each section with our recommendation as to who and where the product is good for. The individual product sections are relatively short as there’s not much difference between the openers. Our Buyer’s Guide rounds this out by examining the different features of greenhouse vent openers that do make a difference.
Our Best Pick is the Bayliss XL Auto Vent Opener. This is a mechanical solar-powered window opener. If you have either a wood or an aluminium greenhouse, this vent opener will operate comfortably there. This is probably the best choice for most greenhouses.
The Runner-up for Best greenhouse automatic window opener is the Palram Greenhouse Accessory Automatic Vent Opener. This is also a mechanical vent opener and it’s specially made for Palram greenhouses which are very popular in the UK and many people will have this brand of greenhouse already so this is obviously a good model to start with for those people.
If your greenhouse is on the smaller side and you’re looking for a good quality budget automatic vent opener, take a long look at this one. If you have a polycarbonate greenhouse, the vents are usually much lighter so we recommend the Bayliss Mk7 Triple Spring variant which we also review below. This is also better if your greenhouse is exposed to high winds.
This automatic vent opener could be a winner if you own, or are buying, one of the popular Palram greenhouse.
Top 5 Best Greenhouse Automatic Vent Opener Reviews
1. Bayliss XL Auto Vent Opener
The Bayliss XL Auto Vent Opener is a solar-powered vent opener that operates mechanically. It’s received good reviews and Bayliss is a company with an excellent reputation.
This automatic vent opener is made from anodised aluminium which makes it resistant to corrosion. The heavy spring holds everything in place firmly. The opener is thus resistant to damage caused by high winds when the window opens and closes.
The Bayliss XL automatic vent opener is suitable for greenhouses made from wood or aluminium. It’s also simple to install as you screw the opener into the wooden frame or clamp it onto the aluminium struts without the need for any drilling. However, online reviewers state that, depending on the model of your greenhouse, you may have to make custom adjustments to the unit and fittings but for most this won’t be something you will need to do.
This vent opener is suitable for opening hinged windows up to 60cm by 60cm. That’s the standard size of many greenhouse windows. The window has to weigh less than 5.5kg which is usually the case and its maximum opening with this vent opener is 30cm. Ensure that the weight and opening space of your vent window suits these measurements. You adjust the temperatures at which the opener opens and closes by simply turning a knob. If a cold spell of weather is predicted, you may want to keep your greenhouse warmer than usual.
Bayliss gives a list of its greenhouse models in which their XL vent opener will work. The vent opener comes with a full two-year manufacturer’s warranty for all parts. If the power tube (with the oil inside) breaks after this period, you can order replacement tubes from Bayliss; you don’t have to replace the whole unit which is something you cannot do with most other models.
- Solar-powered greenhouse vent opener so you don’t need an electric hook-up.
- Screws into wood and clamps onto aluminium greenhouses without the need for drilling.
- Anodised aluminium construction for durability and corrosion resistance.
- Spring controlled so avoids damage from high winds.
- Suitable for opening hinged windows/vents up to 60cm by 60cm – a standard size in many greenhouses.
- Adjustable temperature controls by turning a knob to handle changes in the weather.
- Budget model so you don’t need to invest more money than your greenhouse cost into it.
- Manufacturer-backed full two-year guarantee for all parts.
- Not suitable for side vents.
- Instructions are a little inadequate.
- Installation problems with older greenhouses.
The Bayliss XL Auto Vent Opener is a mechanical piston model that’s powered by solar power. On its website, Bayliss lists its greenhouse models that this vent opener fits (and doesn’t fit). Check this out before you purchase the XL auto vent opener. Handling a maximum payload of 5.5kg (that’s the weight of the vent window that it can open), this vent opener is limited to windows that are no larger than 60cm by 60cm.
We’ve made the Bayliss XL Auto Vent Opener our Best Pick of greenhouse automatic vent openers.
If you have a small to medium size greenhouse and are looking for a quality automatic vent opener at a budget price, this one could be for you. If you have a polycarbonate greenhouse so. the vents are lightweight or you have your greenhouse exposed to high winds, we recommend using the Bayliss Mk7 Triple Spring variant which we review below.
2. Palram Greenhouse Automatic Vent Opener
The Palram Greenhouse Automatic Vent Opener is another piston vent opener that is powered by the sun. It’s specially designed for the Palram line of greenhouses (except for discontinued models). If you have this brand of greenhouse, you know that this vent opener will fit. If you have another greenhouse brand, it may fit that as well.
The temperature at which the vent window opens is adjustable to suit different seasonal days. Choose a starting point for opening in the range of 12°C to 15°C. Installation of this automatic vent opener isn’t too bad, though some users say that the fixing screws are difficult to install and they’re in tight places that are tricky to get to.
- Mechanical piston system with solar power so you don’t need your greenhouse by an electric outlet.
- Start opening point is 12°C to 15°C for varied weather conditions.
- Fits any Palram greenhouses except for discontinued models.
- Fixing screws difficult to install.
The Palram Greenhouse Accessory Automatic Vent Opener is specially designed to fit in the Palram current line of greenhouses. If your Palram greenhouse is somewhat old, check the manufacturer’s website to see if it’s been discontinued. If you have another brand of greenhouse, this automatic vent opener may work with that as well.
This Palram Greenhouse Accessory Automatic Vent Opener is a good choice for you if you already own a Palram greenhouse which many people probably do as there very popular.
3. Grow It Gardman Greenhouse Auto Vent
The Grow It Gardman Greenhouse Auto Vent is yet another mechanical vent opener with a piston that uses solar power to move. Most aluminium or polycarbonate greenhouses benefit from the ventilation provided by this vent opener. However, it may not fit older greenhouses that have a different structure to current ones.
This Grow It greenhouse auto vent has a long-lasting metal construction that’s both rot and rust-proof. The unit comes in a green finish that looks smart and is a change to the usual silver colour. The opening temperature is adjustable so you can change it with the seasons. This auto vent suits greenhouses with dimensions of 182cm by 182cm or larger. The air from the ventilation reaches all your many plants.
- Durable metal construction that stands up against rot and rust.
- Mechanical piston powered by solar energy so there are no wires to worry about.
- Works with most polycarbonate and aluminium greenhouses.
- Wax cylinder can be easily removed for winter storage.
- Adjustable temperature for opening the vent to suit outside conditions.
- May not fit older greenhouses.
- Not for wood frame greenhouses.
The long-lasting metal construction of the Grow It Gardman Greenhouse Auto Vent keeps it safe from rot and rust. Its green finish adds style to your greenhouse alongside all your plants. If you have a greenhouse, that’s 182cm by 182cm or larger, this autovent will keep it well ventilated. Remember to store the easily removed wax tube over the winter so as to not harm the contents with low temperatures.
If you have an aluminium or polycarbonate greenhouse that’s fairly large, take a look at the Grow It Gardman Greenhouse Auto Vent.
4. Bayliss Mk 7 Window Autovent
The Bayliss Mk7 Window Autovent is the standard model in a line of Mk7 autovents. It’s similar to our Best Pick, the Bayliss XL Auto Vent Opener, but handles slightly heavier vent windows.
It’s also more suitable than our best pick for polycarbonate greenhouses because the vents are lightweight or if you have your greenhouse exposed to high winds.
A mechanical solar-powered piston powers the Bayliss Mk7 Window Autovent. This automatic vent opener comes in a satin anodised finish for resistance to rust and corrosion.
You can install this vent opener in aluminium or wood greenhouses just like our best pick so it works with whatever style of greenhouse you have.
However, some people may find installation can be difficult as you need small fingers to get into the small spaces to put screws in. Depending on your type and age of greenhouse, you may need to custom install the Bayliss Mk7, maybe drilling new holes or using longer screws.
Opening and closing vent windows of up to 60cm by 60cm are no problem for this autovent – as long as they weigh 6kg or less. The vent window opens to a maximum of 30cm to let an adequate volume of fresh air in. And you can set the vent window opening temperature anywhere from 12°C to 25°C. Spring, summer, autumn – this is a three-season vent opener.
The Bayliss Mk7 comes with a two-year manufacturer’s warranty. If you do need to replace part of the unit, Bayliss sells the parts individually. You don’t have to spend your money on a complete extra unit to get spare parts.
- Opening greenhouse roof windows 60cm x 60cm
- The payload is up to 6kg for heavier windows.
- The mechanical piston works on solar power so great for a sunny summer.
- Opens the window to a maximum gap of 30cm for adequate ventilation for many plants.
- Installs into wood or aluminium greenhouses.
- The adjustable opening temperature of between 12°C and 25°C lets you ventilate your greenhouse throughout the growing seasons.
- Two-year warranty against faulty manufacture.
- Difficult to install.
- May need to custom fit the vent opener.
The Bayliss Mk7 Window Autovent (standard model) is similar to our Best Pick, the Bayliss XL Auto Vent Opener. It has many of the same characteristics but can open and close a heavier window and as mentioned, is better for greenhouses with polycarbonate windows as it closes easier without the weight of the usual window glass. You have the ability to choose the temperature at which to open the ventilation – from 12°C to 25°C. This covers the needs of a wide range of plants at different stages of their growth.
If you have a greenhouse with heavy windows, perhaps glazed with toughened safety glass, the Bayliss Mk 7 Window Autovent may suit your needs.
5. Gardening-Naturally Automatic Greenhouse Window Opener
The Gardening-Naturally Automatic Greenhouse Window Opener is made from aluminium-coated zinc steel. These materials give the vent opener sturdiness and durability.
This Gardening-Naturally automatic vent opener handles larger and heavier window vents than the other products in this review. It has an opening force (window weight) of 7kg and opens to a maximum of 45cm. This maximum opening is reached when the temperature of the greenhouse is around 30°C. You don’t have to worry about your plants being fried on really hot days.
The range of opening temperatures is from 17°C to 25°C. The specific temperature at which the vent opens depends on how you set up the autovent. Installation of this model is quite easy, though some users report that the instructions are not easy to follow. However, YouTube videos are available if you need help so at least you have something to refer to.
- Piston vent opener that runs on solar power so you don’t need an additional power source such as a battery.
- Aluminium zinc-coated steel construction that makes this vent opener durable.
- The opening temperate range is from 17°C to 25°C; you set up what you want it to be.
- The window opens to a maximum of 45cm depending on how you adjust the unit.
- Opening force (payload) is 7kg to operate heavier windows.
- Warranty is for two years.
- Instructions are not clear.
The Gardening-Naturally Automatic Greenhouse Window Opener is constructed from aluminium-coated steel for years of opening and closing greenhouse vents and windows. The wide range of opening temperatures offers ventilation on cooler days as well as warmer ones. This window opener’s payload (weight of the window it can raise) is more than the other models in our review. It also opens a gap of up to 45cm, again wider than our other products here.
If you have a larger greenhouse with fairly heavy windows, consider the Gardening-Naturally Automatic Greenhouse Window Opener.
Good greenhouse ventilation is important to keep your plants from getting too hot, in every kind of weather. You can always keep track of the temperature yourself and run in and out to open the window vents as your plants need. But are you going to remember to do that throughout all of spring, summer and autumn?
Greenhouse automatic vent openers (sometimes called autovents) take all the worry out of giving your plants the correct ventilation and keeping them at an optimum temperature. Automatic vent openers open the vent/window at a particular temperate and close it when the weather cools off.
The individual reviews in this article show that autovents are similar to each other. The small differences may not be immediately obvious. This Buyer’s Guide points out the features to look for in an automatic window opener so you choose the best model for your greenhouse.
How an automatic vent window opener works
Window openers can be mechanical and solar-powered or electric. All the vent openers in this article are mechanical ones and we’ll focus on that. However, unlike mechanical openers, electric ones need a power source to power the strong electric mower that opens the windows. Electric vent openers also need an external temperature gauge to tell when the temperature reaches the pre-set limit or when it changes. These types of vent openers are usually installed in large commercial greenhouses.
In contrast, the way in which mechanical automatic openers operates is quite basic but ingenious. They work from a metal cylinder that contains mineral oil which expands when it’s hot. The expanding wax pushes a piston which opens the auto vent and opens the window. As the temperature drops in the greenhouse and the wax cools, a spring contracts and the window is closed and the piston is reset.
These mechanical vent openers don’t need a power source or an external temperature sensor. The sun heats up or cools the wax and the opener does its job. You usually adjust the temperature at which the window is opened by turning the adjustment knob on the end of the unit.
Automatic vent openers are usually made out of metal. This gives them strength and resilience. The units that are powder-coated, coated with aluminium or anodised re also rust-resistant. Check that all the fastenings and fittings have a galvanised coating so you can safely leave the vent opener out in the winter. The galvanised metal also protects them from rusting from any humidity in the greenhouse.
Look also at the oil cylinder, the piston and the spring. They should operate smoothly together with no snags or scratches. The cylinder wears out over time and loses its temperature sensitivity. You need to replace the cylinder when this happens. Some manufacturers sell the cylinder by itself; others require you to buy another unit. If you’re on a budget, or just don’t want to spend more than you need to, look for automatic window openers with replaceable cylinders are ideal and much more environmentally friendly.
Lifting capacity and window size
Lifting capacity (aka load capacity) and the size of the window that can be opened and closed are related. Generally, the larger the window, the heavier it is. However, your large windows may be lightweight if the glazing is of polycarbonate or other plastics. To be sure that you’re buying an automatic vent opener that can open your vent, measure the window for its dimensions and find out how much it weighs. (At the manufacturer’s website or in a review somewhere.)
Many of the vent openers in this review state that they handle windows up to 60cm by 60cm that’s the standard size for most greenhouses. The openers in this review can move vents with a weight ranging from 5.5kg to 7kg. If you have very large or very heavy greenhouse windows vents, look for an opener that handles weights above 7kg.
The whole point of automatic vent openers is to keep your plants at the best temperature for them. Most openers have a temperature range for you to choose the opening temperature from. When the greenhouse reaches that temperature, the window opens. The maximum opening of the window is usually upwards from a set temperate. For example, the opening temperature range may be from 15°C to 25°C and the maximum opening of the window may be at 30°C.
Some vent openers have a wider range for opening and a higher maximum for full extension. Be sure to buy a vent opener with a range of opening temperatures that suit your climate and the plants that you grow.
You do enough already to care for your plants and to give them the best possible growing conditions. Reduce some of that load with a greenhouse automatic vent opener. This type of vent opener opens and closes your vent for you according to the temperature. The vent openers in this review are all mechanical ones that are solar powered in that they react to the sun’s heat. There are no wires to hook up and no batteries to keep charged. Different models can manage various sizes and weights of window vents. Be sure to find out what conditions your new automatic window opener needs to operate in.
Our Best Pick is the Bayliss XL Auto Vent Opener. This is the least expensive of the models in this review but delivers most of the same features as the other openers.
The Palram Greenhouse Accessory Automatic Vent Opener is our Runner-up. This is designed to work with Palram greenhouses.
If you’re interested in buying a new greenhouse, or more accessories, to go along with your automatic greenhouse vent opener, check out our other relevant reviews.
Last update on 2021-10-16 / Affiliate links / Images from Amazon Product Advertising API