Greenhouse ventilation is a crucial aspect of maintaining a healthy and productive growing environment. Proper ventilation helps to regulate temperature, humidity, and carbon dioxide-to-oxygen ratios, which are all essential for plant growth. In this video, we’ll discuss the importance of greenhouse ventilation and the different types of ventilation systems available.
• Hoop house ventilation is essential to balance the internal heat and avoid plant stress.
• Ventilation helps regulate temperature, manages humidity, and ensures a continuous flow of fresh air for plants to thrive.
• Ventilation includes active (mechanical/electrical) and passive (unpowered) methods.
• Active ventilation requires electricity, can be expensive to install and operate, and should have a total fan capacity equal to twice the floor area of the greenhouse.
• Passive ventilation relies on airflow through vents, windows, and doors, is energy-efficient and cost-effective, and should take into account elements such as climate, size/design of the greenhouse as well as plant needs.
• A combination of both mechanical and natural ventilation works best with regular monitoring and adjustments necessary for optimal conditions.
GREENHOUSE VENTILATION CALCULATOR
The University of Massachusetts recommends that your total fan capacity should be 2 times the floor area of your greenhouse. Fan capacity is measured in cubic feet per minute (CFM) of air moved. So in a 30' x 100' greenhouse, the fan capacity should be 30' x 100' x 2 = 6000 CFM.
From there you’ll need to calculate the CFM of your fans. The number of fans can be calculated by dividing the capacity needed by the output of one fan.
Greenhouse fans are generally available in 12", 24", and 36” diameter blades. Fan output and efficiency increase with an increase in blade diameter. Here’s the capacity for our greenhouse fans:
12” Fan - 900 High CFM
24” Fan - 4450 High CFM
36” Fan - 8860 High CFM
Using the initial example, let’s assume we’re going to purchase 24” fans. To calculate the number of fans needed = 6000 CFM divided by 4450 CFM/fan = 1.35 fans. Use 2 fans.
Also, remember that fans and vents go together. For every fan you install, you need an equal number of vents. So if you’re using 2 fans, be sure to also install 2 vents.
GREENHOUSE VENTILATION FAQ
What is the best way to ventilate a greenhouse?
The best way to ventilate is through a multi-prong approach. Rolling up the sides of your hoop house or opening windows and doors on the greenhouse are good ways to start. Passive ventilation methods have distinct limitations. They take time each day to roll up and roll down. You’ll have to always be on hand to manually adjust airflow depending on the weather and time of day.
This is where fans - especially ones connected to a temperature control unit - come into play. Fans not only maximize greenhouse ventilation, but they allow for a more hands-off approach. Any bit of time saved during busy farm days is worth it!
Don’t forget the value of shade cloth. While not a ventilation mechanism, shade cloth is very important to maintain proper temperatures. To understand the best shade cloth for your growing situation be sure to read our article on Monofilament vs. Tape Shade Cloth.
At what temperature should I vent my greenhouse?
The ideal temperature for a greenhouse in the summer is 75-85 during the day and 60-70 at night. During the winter this generally decreases to 60-70 during the day and around 45 at night. Anytime your greenhouse is exceeding these recommendations, you’ll need to vent it.
Adequate greenhouse ventilation is crucial for maintaining a healthy and productive growing environment. By understanding the importance of airflow, selecting the right ventilation method, and optimizing your system, you can create the ideal conditions for your plants to thrive. Keep in mind that regular monitoring and adjustments may be necessary to ensure ongoing success. With the right ventilation strategy in place, you'll be well on your way to a flourishing greenhouse.
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