How to Calculate CFM Greenhouse Specifications
To successfully grow plants and cuttings, a greenhouse must maintain a certain air pressure and exchange rate. The air exchange rate is the number of times that all of the air in the greenhouse is exchanged in a certain amount of time (hours or minutes). The industry standard is one full exchange per minute (i.e., all of the air in the greenhouse is exchanged every minute). That may seem like a lot, but in reality, many greenhouse fans can easily handle that kind of volume, especially with a multiple fan setup. To calculate the fan CFM (cubic feet per minute) requirement for your greenhouse, follow these simple steps. Does this Spark an idea?
Other People Are Reading
Instructions
-
-
1
Calculate the volume of your greenhouse. Multiply the width by height by length in feet of the greenhouse to get the overall air volume of the greenhouse. Use this number as a starting point for the CFM you will be looking for in a fan.
-
2
Correct for environmental factors by calculating F-house (F-house = elevation (feet) X light (square feet) X average temperature). Multiply F-house by the starting point CFM that was calculated in step 1.
-
-
3
Search for applicable fans and determine their setup. If you have a greenhouse with dimensions of 10-by-20-by-8 feet, then your standard CFM would be 1,600 CFM. If you adjust for the greenhouse being at 10 feet above sea level, with 10 feet of light and an average temperature of 20 degrees, you get 32,000 CFM (10 feet X 10 feet X .20 = CFM). Divide your final number by the number of fans you plan on having. In our example, we will have eight fans, which means we need to find fans with a 4,000 CFM rating.
-
1
Tips & Warnings
Most companies provide online exhaust fan calculators that are accurate and easy to use. Check out the links in Resources to find one that will work for you.
