is based on a specific formula regardless of your plant types and climate
zone. You may vary shading and misting to accommodate plant needs and your
The exhaust fan should change the air in the greenhouse
in 1-1/2 minutes. Fan capacity is rated in Cubic Feet per Minute (CFM).
For your correct fan size in CFM, calculate your greenhouse Volume:
Length x Width x Average Height = Volume.
For Average Height, measure halfway up a roof rafter and
then measure straight down to the floor. This vertical measurement is
the Average Height.
Multiply the Volume by 0.75 for your fan CFM.
Now Select a fan with a CFM rating near or greater than
your calculation. Our larger fans can be slowed with a fan speed control.
Caution: A fan that is too small will provide very little
Some shading will be required in warmer months, and misting
for evaporative cooling may also be necessary.