$42 210CFM fan

Didn't know if anyone else knew about these, they're 120mm computer fans that put out 210CFM (equivalent to a 4" inline fan that retails for more than 100) and uses 2.7amps of 12v current. Just need an AC/DC adapter with at least 3 amps.

Here's the fan
http://www.newegg.com/Product/Product.aspx?Item=N82E16835706022

and the power adapter
http://www.parts-express.com/pe/showdetl.cfm?partnumber=320-312&source=googleps

thats over $60 before shipping . I bought a house fan from Walmart for $15 and it blows plenty of air and is very quiet . I have two . One for exaust and one to blow across the girls to stir up the air .

I use a inline booster fan for my aircooled hood and exhaust and they are 200 to 300 CFM variable speed and were only 35 dollars each
get them are home depot or princess auto

Those computer fans really don't do much, you might as well open a hole in your grow room and use a regular fan like dadio said.