When you pull to much air out of your space, it causes a negative pressure in the grow area.. If your exhaust is 4 or 6 inches and your space is like 5x7 you would need a 6 inch intake to level the pressure out.My 465 cfm fan would raise the floor up when I turned on the fan. It was sealed that tight.I had a four inch intake.. Changed to a 6 and all is well...:thumbsup:


Ga Grown!
GaGrown Reviewed by GaGrown on . BATHROOM EXHAUST FANS....GOOD/BAD? Hello everyone...im still trying to work some bugs out of my growroom design! I got talked into using a 8" room fan as an exhaust fan (placing the backside of the fan in the grow space, blowing out!) Anyways...it was a terrible idea and it sucks way way way to much air out no matter how much I choke it down! I now have a 8" hole in the top of my box...has anyone used a bathroom exhuast fan? what issues will I run into? Looks like I can get a decent one for around $50! Thank Rating: 5