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Greenhouse Ventilation

Ventilation is perhaps the most important component in a successful greenhouse. Without proper ventilation, greenhouses and their plants become prone to a myriad of problems. This is because ventilation serves four major purposes within the greenhouse. First of all, it helps to regulate temperature. It also ensures that your plants get plenty of fresh air that they can use to photosynthesize. Additionally, good ventilation prevents pest infestations and will encourage important pollination within the greenhouse. If you find your plants struggling in any of these areas, selecting the proper fans and vents for your greenhouse can help to alleviate the problem.

greenhouse exhaust fan Temperature

Without good ventilation, any greenhouse can become too warm, even in relatively cool weather.  Believe it or not, more plants die from excess heat within a greenhouse rather than from the cold.  Many plants are extremely sensitive to heat and will either wilt, stop growing or die. Having vents placed throughout the greenhouse will help to keep the temperature more consistent and will allow some of this heat to naturally escape. If heat is an especially big concern in your greenhouse, consider an exhaust fan that will push stale air out the greenhouse, encouraging fresh air to flow in. Using an evaporative cooler in conjunction with a high-quality exhaust fan is the best way to cool your greenhouse in hot climates.

Fresh Air

All plants need carbon dioxide in order to photosynthesize. If your greenhouse does not have good air flow, the plants will not have the carbon dioxide they need to produce the sugars they use as food. Your greenhouse needs vents to allow fresh air to move in, but you should also have some kind of circulation fan to keep the air moving throughout the entire greenhouse so that it will reach all of your plants.


Many people fail to realize how ventilation affects pests within greenhouses. Not only does poor ventilation cause plants to become sick and fall victim to opportunistic bugs, but many bugs will also find your greenhouse too comfortable if air is not properly circulating. In fact, by placing fans like this high-powered circulation fan near plants plagued by pests such as white fly, you can cause these pesky populations to leave your greenhouse altogether.


In nature, wind is constantly causing pollination to occur. Because your greenhouse does not naturally have this wind, it is important to substitute it with good fans. Moving air will gently shake the plants, allowing pollination to occur. This is especially important with plants such as tomatoes, which are self-pollinating. If you notice that your favorite plants are not fruiting, this is a sign that you need to increase air flow in your greenhouse. The gentle pressure on your plants caused by the air flow will also encourage your plants to develop sturdier stems and root systems, improving their overall health. You might also want to consider a hand pollinator to increase pollination like the Vegibee.

Choosing Fans and Vents

An exhaust fan is an important way to help decrease the temperature and improve overall success in your greenhouse. Ideally, exhaust fans should be placed towards the roof of the greenhouse, opposite the door. If your particular greenhouse does not allow you to add exhaust fans, be sure to add extra circulation fans.

Depending on your particular model, you may already have base or roof vents in your greenhouse. These are extremely important and should always be left open during warm weather. It is best to add solar openers to these vents so that they will automatically open and close when necessary. If your particular greenhouse offers the ability to add extra vents, often times this is advantageous and highly suggested in warm climates. Ideally, there should be at least one large vent placed near or on the roof of the greenhouse in order to allow heat to escape. There should also be several vents placed around the perimeter of the greenhouse, near the base. This allows for the best, most natural type of ventilation – cross-ventilation.

In cross-ventilation, cool air freely enters the greenhouse through the vents placed near the base and flows across the greenhouse towards the vents near the top of the greenhouse. Heat escapes most efficiently in this manner, while your plants receive a consistently fresh supply of carbon dioxide. Natural convection causes cross-ventilation, which maximizes the circulation you can achieve by vents alone.

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