Does My Greenhouse Need Ventilation?

Creating the proper ventilation system for a greenhouse is a vital part of keeping plants healthy and productive. This can be done by installing manual or electric ventilation systems.

Regardless of the size of the greenhouse, proper ventilation is important to ensure that the plants thrive. Having vents that allow air to circulate helps the plants to grow properly.

Although keeping plants warm is important, failing to maintain the proper ventilation can cause them to die. Having the proper ventilation system can also help keep the plants from getting too hot.

Good ventilation is important in maintaining a healthy and optimal greenhouse environment. In Australia, roof ventilation is commonly achieved by using vents and other systems to cool the air coming from the roof.

Why You Need Ventilation

Learning how to use a greenhouse is a process that involves trial and error. It will help you understand why ventilation is so important to the success of your plants.

Temperature control

Gardeners who have never used a greenhouse before are often amazed at how quickly it can become extremely hot inside. There must be a method for the hot air to leave in order to keep the temperature within the appropriate range for the plants you are cultivating. While most plants benefit from the extra warmth provided by a greenhouse, too much heat will kill them.


To photosynthesize, plants require fresh air. Plants, in addition to water and nutrients, require a steady supply of carbon dioxide from the air to create the sugars they require to exist. Fresh air may circulate around all of the plants in a vented greenhouse. Plants will struggle to photosynthesize if there isn’t enough air.


Pollination success is improved. Many plant species, such as tomatoes, eggplants, and peppers, rely on wind to distribute their pollen. Because plants are fully protected from the wind within a greenhouse, they may not produce fruits because their blooms are not pollinated.


When there is no breeze, insect pests like whitefly are at ease. Your greenhouse will attract all of the pests in your plants if there isn’t enough air movement. Powdery mildew and other fungal infections thrive in warm, humid environments with limited ventilation.

Aids in the development of robust stems and roots in plants. Outdoor plants must contend with the wind, so they build strong stems and root systems to attach themselves to the earth. 

How Many Air Vents You Need

The size of the greenhouse will determine the number of air vents required. In order to keep the air circulating, the greenhouse should have multiple air vents near the roof.

Even inside a tiny greenhouse, high temperatures can damage the plants’ natural defenses. This is why it’s important to have vents on small greenhouse setups.

It is often easy to assume that ventilation is only necessary for big greenhouses. However, in reality, it is always necessary.

Manual ventilation vents are located at the top and bottom of the greenhouse walls. These vents regulate the air flow inside the greenhouse.

As the sun rises, the greenhouse’s warm air rises to the top of the facility, where it can escape through a vent. This allows the plants to use the cool air coming in through the vents.

Exhaust fans and circulation fans are commonly used for electric ventilation. These units work by circulating fresh air around the greenhouse.

Electric ventilation is commonly used because it eliminates the need to close and open the vents each day. Also, it allows you to set a schedule for when the ventilation will start and stop.

Methods to Ventilate A Greenhouse

It is perfectly fine to ventilate your greenhouse using a low-tech method. You may be thinking of investing in a more energy-efficient system or are simply not ready to add a fan.

The height of a structure and the number of vents are both significant factors that affect the capacity of a ventilation system to remove heat from a greenhouse.


Pull the air through the entire structure of the greenhouse to avoid the accumulation of hot air pockets. Having fans placed on high ground is also beneficial for cooling.

Active ventilation is the process of forcing air into a structure. This method is usually carried out by installing fans. They can also be used to circulate air within a greenhouse.

Although active ventilation systems are designed to quickly exchange air, they are limited in their capacity to provide adequate air circulation throughout the structure. Having the right ventilation system and the proper design specifications are important factors to consider when it comes to greenhouse production.

Although fans are energy-efficient, they can also cause problems due to their noise generation. It’s also important to maintain their proper operation.

Natural Ventilation

A good ventilation system for hoophouses is usually found in the form of roll-up sides. This method works well for warm seasons as long as the houses have plenty of space between them.

When polyethylene was first developed, the roof was too big to fit vents. Engineers then came up with the idea of using fans that draw in the air and exhaust it out the other end.

Before the 1950’s, most greenhouse buildings had vents or louvers that were designed to allow air to escape and cool the greenhouse.

Heat loss through the use of wind and temperature gradients is achieved by enclosing a greenhouse with sidewall vents and roof vents. When the wind blows over the roof, a vacuum sucks the heated air out of the vent. If the vents are open, the cool air returns to the floor below.

The buoyancy effect, which is caused by the rising temperature, also helps in ventilation. On cool days, the temperature difference between the hot and cool air is less than 10 degrees. Since this effect is usually non-existent on hot days, horizontal fans should be turned off to prevent destratification of the warm air.

The size of the vents and the floor area should be equal to the ridge vent and the roof’s width should be about 15 to 20% of the floor area. Ideally, the wind should blow over the ridge to create a vacuum and allow the air to escape.

Open-roof greenhouse systems are usually made by major manufacturers. Some of the features that are standard in these types of buildings are vents and controls.

Evaporative Cooling

Clean and low in mineral content water should be used to prevent the pads from getting damaged. A flow rate of 113 gallons per minute is ideal for minimizing water damage.

In most cases, fans draw air through a pad or endwall that’s wet. The material used for the cooling system should have a life of about three years.

Evaporative cooling is a process that uses the heat from the air to remove the moisture from the leaves and other surfaces. It works best when the air has low humidity. In the dry Southwest, it is common to experience significant cooling during the summer months.

During extremely hot weather conditions, the temperature inside a greenhouse can reach 10 to 20 degrees Fahrenheit beyond the outside temperature. This can affect the quality and growth of plants.

A wetting agent should be added to the water to improve the uniform wetting of the pads.

A algaecide is also commonly added to the water supply to prevent the growth of algae within the pads.

An alternative method involves using a fog or fine mist to cool the air. This method works by producing a high pressure mist that’s injected into the air stream. Aside from a pump and fog nozzle, a two-stage system is also commonly used to evenly distribute the water.

Related: Can You Sleep In A Greenhouse?

Natural vs Mechanical Ventilation

A mechanical ventilation system uses a combination of fans and other mechanical devices to circulate and control the air. This type of ventilation system is more controlled than traditional ones. It can maintain the ideal environmental conditions in a greenhouse without the use of wind or thermal buoyancy.

This process generates a vacuum that draws cool air into the sidewall vents located near the ground. When the wind blows over the vents, the air carries fresh air into the vents.

Thermal buoyancy refers to the natural tendency of air to rise as temperature gets higher. This is evidenced by the use of ridge and sidewall vents in a greenhouse.

When it comes to choosing a ventilation system for a greenhouse or other outdoor space, the first step is to consider the type of ventilation system that will best suit your needs.

Sizing for Natural Ventilation Systems

It is generally recommended that the combined area of the ridge vents and the sidewall vents equal 20% of the floor area.

For some greenhouses, such as a hoop house, the use of rolling up the wall to create ventilation is all that is needed. However, for others, such as those made from rigid materials, proper ventilation should be carried out using guidelines.

Before you can properly install and operate a ventilation system for a greenhouse, it is important to consider if the facility is seasonal or year-round. For instance, if it’s used year-round, it’s best to size up the ventilation system for the hotter summer months.

Ideally, you should buy equipment that has variable speed fans or thermostats to allow it to be used throughout the year.

Related: What Are The Disadvantages Of Greenhouse?

Is GreenHouse Ventilation Important?

One of the most critical factors when it comes to constructing a greenhouse is ventilation. This is because adequate ventilation can help keep the greenhouse warm and productive.

Having the proper ventilation can help regulate the humidity and temperature inside a greenhouse. It’s also important to keep the plants’ air supply at a constant level.

A well-ventilated greenhouse can also help prevent pests and diseases from spreading. It’s also beneficial for the plants’ pollination rates.

The ventilation system of a greenhouse is a crucial component of plant health and crop production. Many novice gardeners do not realize the importance of this system and its various benefits.

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