If you use your greenhouse during the summer months, a reliable greenhouse ventilation system is essential. Proper ventilation does more than just circulate air - it helps regulate temperature, reduce humidity, and keep plants healthy. A complete system usually includes exhaust fans, intake shutters, shutter motors, and a thermostat that controls when the components operate.
In a standard setup, exhaust fans are installed on one end of the greenhouse, and the intake shutters are placed on the opposite end. This design allows cool, fresh air to enter from outside, flow across your plants, and exit through the fans. For best results, fans and shutters should be positioned between waist and head height. Some growers install the exhaust fans above the greenhouse door, which is acceptable, but intake shutters should not be installed too high. Placing them high can draw hot air from the top of the greenhouse down onto the plants. If you need to cool the upper section, a smaller secondary fan system can be installed near the gable.
Calculating Your Ventilation Requirements
To size your greenhouse ventilation system correctly, you need to determine the CFM (cubic feet per minute) requirement. Here is an example:
If your greenhouse measures 10 feet wide by 20 feet long with a peak height of 8 feet and a sidewall height of 6 feet, use this calculation:
10 x 20 x 7 (average of peak and sidewall height) = 1,400 CFM
This means your greenhouse requires a fan, or a combination of fans, that can move about 1,400 cubic feet of air per minute for proper air exchange.
Choosing Fans, Shutters, and Accessories
We offer convenient greenhouse ventilation packages that make it easy to select everything you need, but you can also customize your system. When creating a custom setup, begin by choosing the correct exhaust fan using the specifications chart. Once you know the fan size, ensure that your intake shutters can handle more airflow than the fan provides. A good guideline is to size your intake area about one and a half times larger than your fan.
For example, a 16-inch exhaust fan should be paired with either one 24-inch intake shutter or two 20-inch shutters. Using multiple shutters helps distribute airflow evenly and prevents stagnant areas inside the greenhouse.
Thermostat and Wiring Setup
The thermostat must be wired to both the fan and the shutter motors so that they turn on together. This coordination ensures consistent cooling and efficient airflow. If you prefer a plug-in style, you can purchase a corded thermostat along with corded fans or motors. Be sure to select the corded option for each component and purchase one thermostat per corded item. Our standard ventilation kits include the wired versions for a clean, permanent installation.
By properly sizing and installing your greenhouse ventilation system, you will maintain a balanced growing environment and keep your plants healthy all season long.
- Sarah H., Greenhouse Megastore Team
