How To Determine What Size Fan & Filter You Will Need For Your Space
We recommend to change the air in your grow room once every 3 minutes or more. First you will need to calculate your cubic feet of your space. To do that, just multiply your rooms length, width and height. Once you get your cubic feet you want to divide that by 3. That will give you your starting point for sizing your fan. See below for example.
Example: Room Length (8) x Room Width (8) x Room Height (8) = 512 Cubic Feet. Divide 512 cubic feet by 3 to get your minimum recommended fan and filter combo. For this example you will want a fan that will is capable of exhausting 170 cubic feet per minute (CFM) or more. This will be the absolute minimum CFM for exchanging the air in an indoor garden. Remember that oversizing slightly is better than undersizing.
Other things to consider are: Will you have a carbon filter? If so add an additional 25% to your minimum CFM requirement. What type of lighting are you using? Add an additional 5% per air cooled light and about 10-15% per non air cooled light.