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Not sure what size exhaust fan you need for your greenhouse kit? Our greenhouse fan size calculator does all the work for you. Just enter in the greenhouse dimensions into the fan calculator below. We offer complete greenhouse exhaust fan systems with thermostats, or you can purchase exhaust fans and controls separately.
Greenhouse Fans Chart

This chart shows the typical # of degrees warmer the inside of the greenhouse will be versus the outside air temperature if the ventilation system is running constantly.

- Chart assumes the exhaust fan and intake(s) are installed in opposite end walls (as shown below without any other openings near the fan).

- Individual results may vary. Chart does not take into account factors that can affect results like greenhouse shape, covering type, and area's sun intensity.
Greenhouse Fan Size Calculator
Length of Greenhouse (feet)
Greenhouse Exhaust Fan
Width of Greenhouse (feet)
Peak Height of Greenhouse (feet)
W x L x H x 0.85
Fan CFM Needed - This is the minimum recommended exhaust fan CFM (Cubic Feet per Minute) rating for your greenhouse. A fan this size will exchange the air in your greenhouse at least once per minute which is recommended for venting small greenhouses.
Greenhouse Evaporative Cooler CFM Calculator
Cooler CFM needed with no shade cover on the greenhouse.
Cooler CFM needed with a 50% or higher shade cover.
Note: You need to have Javascript enabled on your browser for the calculator to work.


This chart provides you with the recommended intake shutter sizes for the exhaust fan sizes specified. Two shutters are recommended for greenhouses over 10 ft. wide to provide better distribution of fresh air.
Recommended Fan Intake Shutter Sizes
Exhaust Fan Size 1 Intake Shutter 2 Intake Shutters 4 Intake Shutters
12" Exhaust Fan 16" Intake 12" Intakes 8" Intakes
16" Exhaust Fan 20" Intake 16" Intakes 12" Intakes
20" Exhaust Fan 24" Intake 20" Intakes 14" Intakes
24" Exhaust Fan 30" Intake 24" Intakes 16" Intakes
This chart provides you with the recommended exhaust shutter sizes for the evaporative cooler models specified.
Recommended Cooler Exhaust Shutter Sizes
Evaporative Cooler Size 1 Exhaust Shutter 2 Exhaust Shutters 4 Exhaust Shutters
3500VK Cooler 20" Shutter 16" Shutters 12" Shutters
5800VK Cooler 30" Shutter 24" Shutters 16" Shutters

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