what cfm fan would i need to exhaust the air out of a 12x12 ft room?

my local shop says a 250cfm will do.
i think i'll need more on the 500cfm side of things

plus, he says its $320au just for a 250cfm!! thats too much right?


any help appreciated


ps, would i just match a 500cfm fan with a 500cfm carbon filter? or would in need more like a 750cfm filter?

 

http://www.greenhousecatalog.com/fan_calculator.php


i need about 1000cfm