it's pretty easy to figure it out. you multiply the cube feet of your grow area by three and that will give you the approximate CFM rating so you can exhaust your grow area three times a minute.
So for you it would be: 2.5 x 5 x 7 = 87.5, 87.5 x 3 = 262.5
So a fan with CFM rating around 265 would do the trick for you nicely.
As far as the different styles go, my understanding it the vortex style may be most efficient but i would surmise it might be the noisiest.
Bottom line - any fan that does the job is the right fan. |