If you use your greenhouse in the summertime, then you'll most likely need a ventilation system. A ventilation system is more than simply ensuring there's air circulation, it system consists of exhaust fans, intake shutters, shutter motors, and a thermostat. Typically, the exhaust fans are placed on one end of the greenhouse and the intake shutters are placed on the opposite end. This allows cool air to be brought in from the outside, then carried through the length of your greenhouse and out the exhaust fans. It's recommended to place the fans and shutters at a height between waist and head high. Some prefer to place their exhaust fans above the door. This is okay, but you don’t want to place your intake shutters too high because this will bring the hot air that has collected at the top of your greenhouse down to your plants. If you need to cool the top of your greenhouse, then you can place an additional smaller system up in the gable.
To determine the size of your system, you will need to calculate your CFM (cubic feet of air per minute) requirement. For example, if your greenhouse is 10’ W x 20’L with a peak height of 8’ and a sidewall height of 6’, then you would use this calculation: 10 x 20 x 7 (average of peak and sidewall height) = 1,400 CFM.
We have put together ventilation packages for your convenience, but if you would like to customize your system, you can certainly do that. If you are customizing your system, then you'll start with the exhaust fan and reference the specification chart. You always want to make sure that your intake shutters can accommodate more CFM than the fan. A general rule of thumb is to size the intake 1.5 times the size of the fan. For example, a 16” exhaust fan will need a 24” intake, or two 20” intakes. It’s typically better to use more than 1 intake shutter to provide accurate coverage.
The thermostat must be wired to the fan and shutter motors so they can turn on at the
same time. There is an option to buy a thermostat with a cord if you prefer, but you'll need to make sure to select the cord option for the fans and shutter motors and purchase a thermostat for each corded item. Our ventilation packages come with the hardwired versions.
- Sarah H., Greenhouse Megastore Team
